SUPPLY-WATER WARMING SYSTEM

Abstract

A supply-water warming system includes a steam compression heat pump circuit, a heat recovery heat exchanger, a heat source fluid line in which heat source fluid flows in the heat recovery heat exchanger and the evaporator in this order, a water supply line in which supply water flows in the heat recovery heat exchanger and the condenser in this order, a refrigerant flow rate adjustment section controlled based on the superheat degree of gas refrigerant flowing into the compressor and configured to adjust a refrigerant flow rate, a supply water flow rate adjustment section controlled based on the tapping temperature of the supply water flowing out of the condenser and configured to adjust a supply water flow rate, and a control section configured to control the refrigerant flow rate adjustment section and the supply water flow rate adjustment section.

Description

BACKGROUND

1. Technical Field

The present invention relates to a supply-water warming system.

2. Description of the Related Art

In recent years, at business facilities such as factories, efforts for utilizing unused exhaust heat from various facilities have been advanced for the purpose of reducing the amount of emission of carbon dioxide as greenhouse gas. Thus, as described in JP-A-2013-210118 and JP-A-2014-169819, an unused heat utilization system (a supply-water warming system) has been proposed, in which boiler supply water is warmed by a heat pump circuit using hot waste water as a heat source to reduce a boiler fuel usage.

SUMMARY

The supply-water warming system described in JP-A-2013-210118 and JP-A-2014-169819 can be applied not only to warming of the boiler supply water, but also can be applied to warming of water in various production processes. The system according to JP-A-2013-210118 is configured such that heat source fluid (waste hot water) flows in an evaporator and a heat recovery heat exchanger in this order and supply water (cold water) flows in the heat recovery heat exchanger, a supercooler, and a condenser in this order. With this configuration, in the system according to JP-A-2013-210118, the coefficient of performance (COP: an energy consumption efficiency) is successively significantly increased as compared to a typical heat pump system without a heat recovery heat exchanger and a supercooler. Meanwhile, this system has a problem that when the temperature of the heat source fluid reaches a relatively-low temperature (e.g., equal to or lower than 40° C.), the effect of the heat recovery heat exchanger is eliminated.

On the other hand, the system according to JP-A-2014-169819 is configured such that heat source fluid (waste hot water) flows in a heat recovery heat exchanger and an evaporator in this order. With this configuration, in the system according to JP-A-2014-169819, when the temperature of the heat source fluid is higher than that of supply water, the effect of the heat recovery heat exchanger can be provided at maximum. The system according to JP-A-2014-169819 can recover, with a high COP, heat from heat source fluid with a broad temperature range, but a higher efficiency has been demanded for business facilities targeting high-level carbon dioxide emission amount reduction.

The present invention has been made in view of the above-described problems, and an object of the present invention is to further increase an efficiency in a supply-water warming system using both of a heat pump circuit and a heat recovery heat exchanger.

The present invention relates to a supply-water warming system including a steam compression heat pump circuit configured such that a compressor, a condenser, an expansion valve, and an evaporator are connected in an annular shape through a refrigerant circulation line and configured to take out warmth in the condenser by drive of the compressor, a heat recovery heat exchanger, a heat source fluid line in which heat source fluid flows in the heat recovery heat exchanger and the evaporator in this order, a water supply line in which supply water flows in the heat recovery heat exchanger and the condenser in this order, a refrigerant flow rate adjustment section controlled based on the superheat degree of gas refrigerant flowing into the compressor and configured to adjust a refrigerant flow rate, a supply water flow rate adjustment section controlled based on the tapping temperature of the supply water flowing out of the condenser and configured to adjust a supply water flow rate, and a control section configured to control the refrigerant flow rate adjustment section and the supply water flow rate adjustment section.

Moreover, the heat source fluid line preferably has a connection configuration in which after the heat source fluid and the supply water have exchanged heat in a counter flow in the heat recovery heat exchanger, the heat source fluid and liquid refrigerant exchange heat in a counter flow in the evaporator.

Further, the supply-water warming system preferably further includes a suction temperature sensor configured to sense the suction temperature of the gas refrigerant flowing into the compressor, a steam pressure sensor configured to sense the steam pressure of the gas refrigerant flowing out of the evaporator, and a tapping temperature sensor configured to sense the tapping temperature of the supply water flowing out of the condenser. The control section preferably obtains the evaporation temperature of the liquid refrigerant from the pressure sensed by the steam pressure sensor, calculates the superheat degree of the gas refrigerant by subtracting the evaporation temperature from the temperature sensed by the suction temperature sensor, and controls the refrigerant flow rate adjustment section such that the calculated superheat degree reaches a target superheat degree, and preferably controls the supply water flow rate adjustment section such that the temperature sensed by the tapping temperature sensor reaches a target tapping temperature.

In addition, the supply-water warming system preferably further includes a heat source temperature sensor configured to sense the temperature of the heat source fluid before the heat source fluid flows into the evaporator. The control section preferably sets the target superheat degree according to the temperature sensed by the heat source temperature sensor.

Moreover, the control section preferably increases the target superheat degree in a case where it is determined that fluctuation in the temperature sensed by the heat source temperature sensor is great.

Further, the control section preferably decreases the target superheat degree in a case where it is determined that the temperature sensed by the heat source temperature sensor is stable.

In addition, the supply-water warming system preferably further includes a supply water temperature sensor configured to sense the temperature of the supply water before the supply water flows into the condenser. The control section preferably sets the target tapping temperature according to the temperature sensed by the supply water temperature sensor.

Moreover, the supply-water warming system preferably further includes a supply water temperature sensor configured to sense the temperature of the supply water before the supply water flows into the condenser. The target tapping temperature is preferably settable to a value between an upper limit and a lower limit, and the lower limit is preferably a value obtained by addition of a predetermined value to the temperature sensed by the supply water temperature sensor and increasing as the temperature sensed by the supply water temperature sensor increases.

Further, the supply-water warming system preferably further includes one or two bypass lines configured to cause the supply water to bypass the heat recovery heat exchanger and/or cause the heat source fluid to bypass the heat recovery heat exchanger, and a preheating mode switching section configured to switch a preheating mode between a supply water preheating mode in which the supply water and the heat source fluid simultaneously flow in the heat recovery heat exchanger and a preheating stop mode in which at least one of the supply water or the heat source fluid flows in the one or two bypass lines.

In addition, the supply-water warming system preferably further includes a pre-heat-exchanger-inflow supply water temperature sensor configured to sense the temperature of the supply water before the supply water flows into the heat recovery heat exchanger, and a pre-heat-exchanger-inflow heat source temperature sensor configured to sense the temperature of the heat source fluid before the heat source fluid flows into the heat recovery heat exchanger. The control section preferably compares a first sensed temperature obtained by the pre-heat-exchanger-inflow supply water temperature sensor and a second sensed temperature obtained by the pre-heat-exchanger-inflow heat source temperature sensor, controls the preheating mode switching section to execute the supply water preheating mode in a case where the first sensed temperature falls below the second sensed temperature, and controls the preheating mode switching section to execute the preheating stop mode in a case where the first sensed temperature exceeds the second sensed temperature.

Moreover, the control section preferably includes a signal input unit configured to receive a preheating mode specifying signal for specifying a type which is the supply water preheating mode or the preheating stop mode, and a preheating mode switching control unit configured to control, according to the preheating mode specifying signal input to the signal input unit, the preheating mode switching section to execute the supply water preheating mode or the preheating stop mode.

According to the present invention, the efficiency can be further increased in the supply-water warming system using both of the heat pump circuit and the heat recovery heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a supply-water warming system according to one embodiment of the present invention;

FIG. 2 is a block diagram of a control unit of the embodiment;

FIG. 3 is a graph of fluctuation in a temperature sensed by a heat source temperature sensor;

FIG. 4 is a graph of a target tapping temperature settable range in the embodiment;

FIG. 5 is a Mollier diagram for describing a heat pump cycle;

FIG. 6A is a state transition chart of water passage mode switching control in the embodiment;

FIG. 6B is a flowchart of the flow of target superheat degree setting processing in the embodiment;

FIG. 6C is a flowchart of the flow of preheating mode switching control in the embodiment; and

FIG. 7 is a schematic diagram of a supply-water warming system according to a variation of the embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, one preferred embodiment of a supply-water warming system 1 of the present invention will be described with reference to the drawings. Note that a “line” in the present specification is a generic term of a line in which fluid can flow, such as a flow path, a channel, or a pipe line.

FIG. 1 is a schematic diagram of a configuration of the supply-water warming system 1 according to the present embodiment. As illustrated in FIG. 1, the supply-water warming system 1 is a system configured to supply, as hot water W2, supply water W1 warmed by a heat recovery heat exchanger 40 and a heat pump circuit 10 to a hot water demand location.

More specifically, the supply-water warming system 1 of the present embodiment includes a makeup water tank 70 configured to store makeup water W utilized as the supply water W1, the heat recovery heat exchanger 40 and the heat pump circuit 10 configured to warm the supply water W1, a hot water tank 60 configured to store, as the hot water W2, the warmed supply water W1, and a heat source water tank 50 configured to store heat source water W5 as heat source fluid.

Moreover, the supply-water warming system 1 of the present embodiment includes a water supply line L1 in which the supply water W1 flows in the heat recovery heat exchanger 40 and a condenser 12 of the heat pump circuit 10 in this order, a reflux line L2 in which the hot water W2 in the hot water tank 60 flows back to an upstream side with respect to the heat recovery heat exchanger 40, a bypass line L3 in which the supply water W1 bypasses the heat recovery heat exchanger 40, a hot water supply line L4 in which the hot water W2 in the hot water tank 60 is supplied to the hot water demand location, and a heat source fluid line L5 in which the heat source water W5 as the heat source fluid flows in the heat recovery heat exchanger 40 and an evaporator 14 of the heat pump circuit 10.

The makeup water tank 70 is a tank configured to store the makeup water W utilized as the supply water W1 to be warmed by the heat recovery heat exchanger 40 and the heat pump circuit 10, and the water supply line L1 is connected to the makeup water tank 70.

The heat recovery heat exchanger 40 is an indirect heat exchanger configured to perform indirect heat exchange between the supply water W1 flowing in the water supply line L1 and the heat source water W5 flowing in the heat source fluid line L5. More specifically, the heat recovery heat exchanger 40 performs heat exchange between the supply water W1 before passage through the condenser 12 of the heat pump circuit 10 and the heat source water W5 before passage through the evaporator 14 of the heat pump circuit 10.

The supply water W1 in the water supply line L1 passes through the heat recovery heat exchanger 40 and the condenser 12 in this order, and the heat source water W5 in the heat source fluid line L5 passes through the heat recovery heat exchanger 40 and the evaporator 14 in this order.

The heat pump circuit 10 is a steam compression heat pump circuit configured such that a compressor 11, the condenser 12, an expansion valve 13, and the evaporator 14 are connected in an annular shape through a refrigerant circulation line L9 and configured to take out warmth in the condenser 12 by drive of the compressor 11. Refrigerant R flows in the refrigerant circulation line L9.

The compressor 11 has an electric motor 15 as a drive source, and compresses the refrigerant R in the form of gas such as chlorofluorocarbon gas into high-temperature high-pressure refrigerant R. The condenser 12 releases heat to the supply water W1 sent through the water supply line L1 to condense and liquefy the refrigerant R from the compressor 11. The expansion valve 13 decreases the pressure and temperature of the refrigerant R sent from the condenser 12 when such refrigerant R passes through the expansion valve 13. The evaporator 14 absorbs heat from the heat source water W5 sent through the heat source fluid line L5 to evaporate the refrigerant R sent from the expansion valve 13.

As described above, in the heat pump circuit 10, the refrigerant R is vaporized by taking heat from the outside in the evaporator 14, and is condensed by releasing heat to the outside in the condenser 12. Utilizing such a principle, the heat pump circuit 10 draws heat from the heat source water W5 in the evaporator 14, and warms the supply water W1 in the water supply line L1 in the condenser 12.

On the refrigerant circulation line L9 of the heat pump circuit, a suction temperature sensor 17 configured to sense the suction temperature of the gas refrigerant R flowing into the compressor 11 and a steam pressure sensor 18 configured to sense the steam pressure of the gas refrigerant R flowing out of the evaporator 14 are provided.

The expansion valve 13 described herein forms a refrigerant flow rate adjustment section configured to adjust the flow rate of the refrigerant R flowing in the refrigerant circulation line L9 of the heat pump circuit 10. Specifically, the expansion valve 13 is formed as a proportional control needle valve, and changes the stroke of the needle valve by control of the rotational speed of a drive stepping motor to adjust a valve opening degree so that the flow rate of the refrigerant R can be adjusted.

The hot water tank 60 is a tank configured to store, as the hot water W2, the supply water W1 warmed by the heat recovery heat exchanger 40 and the heat pump circuit 10.

The hot water W2 stored in the hot water tank 60 can be circulated and warmed. Specifically, the hot water W2 in the hot water tank 60 can join the water supply line L1 through the reflux line L2, can be warmed again through the water supply line L1 by passing through the heat recovery heat exchanger 40 and the condenser 12, and can return into the hot water tank 60.

The hot water tank 60 includes a hot water temperature sensor 61 configured to sense the temperature of the hot water W2 in the hot water tank 60. Moreover, the hot water tank 60 is provided with a water level detection unit 62 configured to detect a water level in the hot water tank 60. In the present embodiment, the water level detection unit 62 includes an electrode water level detector having multiple electrode rods. Specifically, two electrode rods 621, 622 with different lengths are inserted and held such that the height positions of lower end portions of the electrode rods 621, 622 are different from each other. In the present embodiment, the electrode rods 621, 622 are inserted into the hot water tank 60 such that the height positions of the lower end portions of the electrode rods 621, 622 are sequentially lowered. Each of the electrode rods 621, 622 detects, based on whether or not the lower end portion thereof is in the water, the presence or absence of the water at such a lower end portion.

In the present embodiment, a control unit 100 performs later-described water passage mode switching control by using, e.g., detection results of the hot water temperature sensor 61 and the water level detection unit 62. The contents of such control will be described in detail later.

The heat source water tank 50 stores the heat source water W5 as the heat source fluid of the heat pump circuit 10. For example, hot waste water from a factory is used as the heat source water W5. In the heat source water tank 50, a not-shown overflow line for overflowing a predetermined amount of heat source water or more is provided. Moreover, in the heat source water tank 50, a not-shown water level detection unit configured to monitor whether or not the heat source water falls below a predetermined low water level is provided.

The upstream side of the water supply line L1 is connected to the makeup water tank 70, and the downstream side of the water supply line L1 is connected to the hot water tank 60. On the water supply line L1, a water supply pump 21, a first check valve 23, a first supply water temperature sensor 24, a three-way valve 25 arranged at a bypass line branched portion, the heat recovery heat exchanger 40, a second supply water temperature sensor 26, the condenser 12, and a tapping temperature sensor 27 are arranged in this order from the upstream side.

The rotational speed of the water supply pump 21 can be controlled by an inverter. The rotational speed of the water supply pump 21 is changed so that the flow rate of supply water to the hot water tank 60 through the water supply line L1 can be adjusted in the cases of a later-described once-through water passage mode. That is, the water supply pump 21 forms a supply water flow rate adjustment section in the once-through water passage mode.

The first check valve 23 is provided on the upstream side with respect to a later-described joint portion of the reflux line L2. This prevents the hot water W2 from flowing into a makeup water tank 70 side in a later-described circulation water passage mode.

The first supply water temperature sensor 24 is a pre-heat-exchanger-inflow supply water temperature sensor configured to sense the temperature of the supply water W1 before the supply water W1 flows into the heat recovery heat exchanger 40. The first supply water temperature sensor 24 is provided on the upstream side of a branched portion of the bypass line L3.

The three-way valve 25 is arranged at the branched portion of the bypass line L3. The three-way valve 25 is a section configured to switch whether or not the supply water W1 bypasses the heat recovery heat exchanger 40, and forms a preheating mode switching section. The bypass line L3 is a bypass line in which the supply water W1 bypasses the heat recovery heat exchanger 40.

The second supply water temperature sensor 26 is a supply water temperature sensor configured to sense the temperature of the supply water W1 before the supply water W1 flows into the condenser 12 of the heat pump circuit 10. The second supply water temperature sensor 26 is arranged on the upstream side of the condenser 12, and in the present embodiment, is arranged on the downstream side of the heat recovery heat exchanger 40.

The tapping temperature sensor 27 senses the tapping temperature of the warmed supply water W1 having flowed out of the condenser 12.

The upstream side of the reflux line L2 is connected to the hot water tank 60, and the downstream side of the reflux line L2 is connected to the water supply line L1. On the reflux line L2, a reflux pump 31 (a circulation pump 31) and a second check valve 33 are arranged in this order from the upstream side.

The rotational speed of the reflux pump 31 can be controlled by an inverter. The rotational speed of the reflux pump 31 is changed so that the flow rate of supply water circulating to return to the hot water tank 60 through the reflux line L2 and the water supply line L1 can be adjusted in the case of the later-described circulation water passage mode. That is, the reflux pump 31 forms a supply water flow rate adjustment section in the circulation water passage mode.

The second check valve 33 is, on the reflux line L2, provided on the upstream side with respect to the joint portion between the water supply line L1 and the reflux line L2. This prevents the makeup water W from the makeup water tank 70 from flowing into a hot water tank 60 side in the later-described once-through water passage mode.

With the water supply line L1 and the reflux line L2 as described above, when the water supply pump 21 is actuated in a state in which the reflux pump 31 is stopped, the makeup water W from the makeup water tank 70 can be, as the supply water W1, supplied to the hot water tank 60 while being warmed sequentially through the heat recovery heat exchanger 40 and the condenser 12. This is called the once-through water passage mode. On the other hand, when the reflux pump 31 is actuated in a state in which the water supply pump 21 is stopped, the hot water W2 in the hot water tank 60 can return as the supply water W1 to the hot water tank 60 while being re-warmed sequentially through the heat recovery heat exchanger 40 and the condenser 12, and the water stored in the hot water tank 60 can be circulated. This is called the circulation water passage mode. When both of the water supply pump 21 and the reflux pump 31 are stopped, water passage through the heat recovery heat exchanger 40 and the condenser 12 can be stopped. This is called a water passage stop mode.

That is, in the present embodiment, the water supply pump 21 and the reflux pump 31 form a water passage mode switching section configured to switch a water passage mode among the once-through water passage mode in which the water passes through the condenser 12 without the hot water W2 flowing in the reflux line L2, the circulation water passage mode in which the water passes through the condenser 12 while the hot water W2 is flowing in the reflux line L2, and the water passage stop mode in which water passage to the condenser 12 is stopped.

The hot water W2 in the hot water tank 60 is supplied to the hot water demand location through the hot water supply line L4.

A hot water supply pump 63 is provided on the hot water supply line L4. Examples of the hot water demand location include utilization of the supply water by a steam boiler. Note that the destination of the hot water W2 is not limited to the steam boiler. For example, the hot water W2 produced by the supply-water warming system 1 of the present embodiment may be utilized for rinsing a container for food/drink/drug, pasteurizer sterilization (bottle sterilization) and the like. In this case, a supply of the hot water W2 in a high-temperature range of about 60° C. to 80° C. might be constantly required. According to the supply-water warming system 1 of the present embodiment, for such a purpose constantly requiring a supply of hot water with a temperature in a predetermined temperature range, particularly preferably in, e.g., a system (a system in which non-warmed makeup water is not directly supplied into the hot water tank 60) in which only the warmed supply water W1 is supplied into the hot water tank 60, hot water can be efficiently warmed, and can be supplied while the temperature of the hot water is maintained.

On the heat source fluid line L5, a heat source supply pump 53, a first heat source temperature sensor 54, the heat recovery heat exchanger 40, a second heat source temperature sensor 55, and the evaporator 14 are arranged in this order from the upstream side.

The heat source supply pump 53 is actuated so that the heat source water W5 from the heat source water tank 50 can flow in the heat recovery heat exchanger 40 and the evaporator 14 in this order.

The first heat source temperature sensor 54 is a pre-heat-exchanger-inflow heat source temperature sensor configured to sense the temperature of the heat source water W5 before the heat source water W5 flows into the heat recovery heat exchanger. Note that in the present embodiment, the first heat source temperature sensor 54 is provided on the heat source fluid line L5, but may be provided in the heat source water tank 50.

The second heat source temperature sensor 55 is a heat source temperature sensor configured to sense the temperature of the heat source fluid exchanging heat with the refrigerant R in the evaporator 14. In the present embodiment, the second heat source temperature sensor 55 detects the temperature of the heat source water W5 before the heat source water W5 flows into the evaporator 14. The second heat source temperature sensor 55 is arranged on the upstream side of the evaporator 14, and in the present embodiment, is arranged on the downstream side of the heat recovery heat exchanger 40.

Note that as described above, the heat source fluid line L5 has a connection configuration in which the heat source water W5 flows in the heat recovery heat exchanger 40 and the evaporator 14 in this order.

As described above, the heat source water W5 first flows in the heat recovery heat exchanger 40, and therefore, a preheating amount of the supply water W1 can be increased and heat output of the heat recovery heat exchanger 40 can be increased. Note that as the temperature of the heat source water W5 increases, the effect for increasing the heat output increases.

As illustrated in FIG. 1, the heat source fluid line L5 has a connection configuration in which after the heat source water W5 and the supply water W1 have exchanged heat in a counter flow in the heat recovery heat exchanger 40, the heat source water W5 and the liquid refrigerant R exchange heat in a counter flow in the evaporator 14.

As described above, the heat source water W5 flows in the heat recovery heat exchanger 40 and the evaporator 14 in this order, and flows in the counter flow with respect to a flow direction of the supply water W1 in each of the heat recovery heat exchanger 40 and the evaporator 14. Thus, a heat recovery amount can be maximized.

Next, the control unit 100 of the supply-water warming system 1 of the present embodiment will be described. FIG. 2 is a block diagram of the control unit 100 as a control section of the supply-water warming system 1 of the present embodiment. The control unit 100 includes a target superheat degree setting unit 111, a superheat degree calculation unit 112, a refrigerant flow rate control unit 113, a target tapping temperature settable range determination unit 121, a target tapping temperature setting unit 122, a supply water flow rate control unit 123, a water passage mode switching control unit 130, a preheating mode switching control unit 140, a signal input unit 150, and a storage unit 160.

The target superheat degree setting unit 111 acquires the temperature, which has been sensed by the second heat source temperature sensor 55 as the heat source temperature sensor, of the heat source water W5 as the heat source fluid, thereby setting a target superheat degree according to the temperature sensed by the second heat source temperature sensor 55. For example, in a case where the temperature of the heat source water W5 as the heat source fluid is low, the target superheat degree is set low. In this manner, the circulation flow rate of the refrigerant R can be increased, and even with the low-temperature heat source water W5, the heat recovery amount can be increased.

As described above, a proper target superheat degree is set according to the temperature of the heat source water W5 as the heat source fluid, and therefore, damage of the compressor 11 due to liquid compression and insufficient lubrication can be prevented while the heat recovery amount in the evaporator 14 can be increased.

Moreover, the target superheat degree setting unit 111 may perform the control of increasing the target superheat degree in a case where it has been determined that fluctuation in the temperature sensed by the second heat source temperature sensor 55 is great.

FIG. 3 is a graph of the fluctuation in the temperature sensed by the second heat source temperature sensor 55, the vertical axis of the graph being the temperature T sensed by the second heat source temperature sensor 55 and the horizontal axis of the graph being time t. For example, as illustrated in FIG. 3, in a case where the amount ΔT of change in the temperature T sensed by the second heat source temperature sensor 55 per unit time t0 exceeds a predetermined threshold ΔT0, it is determined that the fluctuation in the temperature sensed by the second heat source temperature sensor 55 is great, and the control of increasing the target superheat degree is performed. Supposing that ΔT0=5° C. and t0=1 min, the control of increasing the target superheat degree is performed when fluctuation greater than 5° C./min occurs. At this point, in a case where the target superheat degree has been set to, e.g., 5° C., the target superheat degree is set to, e.g., 10° C. In an example of FIG. 3, the decrement ΔT of the sensed temperature T per unit time t0 is greater than the predetermined threshold ΔT0. Thus, such a situation is assumed as a situation where the temperature of the heat source water W5 rapidly changes, and therefore, the target superheat degree is changed to, e.g., 10° C.

With this configuration, even in a case where the situation where the temperature of the heat source water W5 as the heat source fluid rapidly changes has been confirmed, the heat pump circuit 10 can be stably driven.

For example, even in a case where the temperature rapidly decreases due to a rapid change in the temperature of the heat source water W5, the target superheat degree is set to a high value so that the refrigerant R can be reliably vaporized in the evaporator 14, and therefore, damage of the compressor 11 due to liquid compression can be prevented.

Further, the target superheat degree setting unit 111 may perform the control of decreasing the target superheat degree in a case where it has been determined that the temperature sensed by the second heat source temperature sensor 55 is stable.

For example, when the temperature T sensed by the second heat source temperature sensor 55 is within a predetermined temperature range for predetermined time, it is determined that the temperature sensed by the second heat source temperature sensor 55 is stable. In a case where the amount ΔT of change in the sensed temperature T per unit time t0 falls below the predetermined threshold ΔT0 for the predetermined time, it may be determined that the temperature sensed by the second heat source temperature sensor 55 is stable. At this point, the control of decreasing the target superheat degree is performed. For example, in a case where the target superheat degree has been set to 10° C., the target superheat degree is changed to, e.g., 5° C.

Note that the lower limit of the target superheat degree is set to, e.g., 5° C. so that damage of the compressor 11 due to liquid compression can be prevented. Moreover, the upper limit of the target superheat degree is set to, e.g., 10° C. so that the circulation flow rate of the refrigerant R can be maintained at a predetermined flow rate or higher and a decrease in the heat recovery amount can be prevented.

As described above, when the temperature of the heat source water W5 as the heat source fluid is stable, the target superheat degree is set to a low value so that the circulation flow rate of the refrigerant R can be increased and the heat recovery amount in the evaporator 14 can be increased.

Note that in the present embodiment, the temperature sensed by the second heat source temperature sensor 55 as the heat source sensor is used for setting the target superheat degree, but the first heat source temperature sensor 54 may be used as a heat source temperature sensor configured to detect the temperature (the pre-evaporator-inflow heat source temperature) of the heat source water W5 before the heat source water W5 flows into the evaporator 14. Although not right before the heat source water W5 flows into the evaporator 14, the first heat source temperature sensor 54 can also indirectly sense the temperature of the heat source fluid exchanging heat with the refrigerant R in the evaporator 14, and the situation where the temperature of the heat source water W5 rapidly changes can be confirmed. Note that the temperature of the heat source water W5 right before the heat source water W5 flows into the evaporator 14 is more preferably measured using the second heat source temperature sensor 55.

The superheat degree calculation unit 112 calculates the superheat degree of the refrigerant R flowing into the compressor 11.

Specifically, the superheat degree calculation unit 112 obtains the evaporation temperature of the liquid refrigerant R from the pressure sensed by the steam pressure sensor 18, and calculates the superheat degree of the gas refrigerant R by subtracting the evaporation temperature from the temperature sensed by the suction temperature sensor 17.

The refrigerant flow rate control unit 113 controls a refrigerant flow rate control section such that the calculated superheat degree (a value calculated by the superheat degree calculation unit 112) reaches the target superheat degree (a value set by the target superheat degree setting unit 111), thereby adjusting the flow rate of the refrigerant R.

For example, as specific control, the feedback control of taking, as a feedback value, the superheat degree calculated in real time by the superheat degree calculation unit 112 to adjust the valve opening degree of the expansion valve 13 such that the calculated superheat degree converges to the target superheat degree is preferably employed. For the feedback control, an arithmetic operation amount algorithm for proportional control (P control) or a combination of integral control (I control) and/or derivative control (D control) with the proportional control can be employed.

As described above, the superheat degree calculation unit 112 accurately calculates the superheat degree of the gas refrigerant R, and the refrigerant flow rate control unit 113 further performs the control of holding such a value constant. Thus, heat output of the condenser 12 to the supply water W1 is stabilized. Consequently, fluctuation in the flow rate of the supply water W1 supplied as the hot water after warming is reduced.

The target tapping temperature settable range determination unit 121 acquires the temperature, which has been sensed by the second supply water temperature sensor 26 as the supply water temperature sensor, of the supply water W1 before the supply water W1 flows into the condenser 12, thereby determining a target tapping temperature settable range according to the temperature sensed by the second supply water temperature sensor 26.

FIG. 4 is a graph of the target tapping temperature settable range determined according to the temperature sensed by the second supply water temperature sensor 26. The horizontal axis of FIG. 4 is the temperature (a pre-condenser-inflow supply water temperature) sensed by the second supply water temperature sensor 26, and the vertical axis of FIG. 4 is a target tapping temperature corresponding to the temperature sensed by the second supply water temperature sensor 26.

The target tapping temperature settable range in the present embodiment is a triangular region indicated as a settable range A. That is, in the present embodiment, the target tapping temperature can be set to a value between the upper limit and the lower limit, and the lower limit is a value obtained by addition of a predetermined value to the temperature sensed by the second supply water temperature sensor 26 and is a value increasing as the temperature sensed by the second supply water temperature sensor 26 increases. More specifically, the lower limit is a value obtained by addition of 15° C. to the temperature sensed by the second supply water temperature sensor 26, and the upper value is a certain temperature, i.e., 75° C. in the present embodiment.

Note that the predetermined value (e.g., 15° C.) for setting the lower limit is stored in the later-described storage unit 160. In this case, this predetermined value is preferably settable by, e.g., external input. Alternatively, the lower limit based on the predetermined value may be stored in the storage unit 160.

As described above, the region as indicated by the settable range A is taken as the target tapping temperature settable range, and therefore, the system is controlled such that a difference in the temperature of the supply water W1 between an inlet side and an outlet side of the condenser 12 is sufficiently great. Thus, insufficient supercooling of the refrigerant R flowing in the heat pump circuit 10 can be prevented, and an excessive flow rate of the supply water W1 can be suppressed in the control of the supply water flow rate adjustment section by the later-described supply water flow rate control unit 123.

Note that even in a case where the target tapping temperature settable range is a rectangular region with constant upper and lower limits, i.e., in a case where the lower limit is constant, if, e.g., a region as indicated by a settable range B illustrated in FIG. 4 is employed, insufficient supercooling of the refrigerant R can be prevented, and an excessive flow rate of the supply water W1 can be suppressed. However, in this case, an acceptable heat source water temperature range and the acceptable target tapping temperature settable range are narrowed.

Note that in a case where the target tapping temperature is a temperature lower than the lower limit indicated by the settable range A, such as a case where the target tapping temperature is not different from the temperature sensed by the second supply water temperature sensor 26 much, there is a probability that insufficient supercooling of the refrigerant R occurs.

This will be described using a Mollier diagram (a p-h diagram) illustrated in FIG. 5.

The vertical axis of the Mollier diagram is a refrigerant pressure (p), and the horizontal axis of the Mollier diagram is a refrigerant specific enthalpy (h). Moreover, the Mollier diagram shows a saturated liquid line Y1 and a saturated steam line Y2. Such a Mollier diagram can show a change in the state of the refrigerant R in a heat pump cycle. The refrigerant R is in a supercooled liquid state (the state of the liquid refrigerant R) on the left side of the saturated liquid line Y1, is in a wet steam state as a gas-liquid mixture state between the saturated liquid line Y1 and the saturated steam line Y2, and is in a superheated steam state (the state of the gas refrigerant R) on the right side of the saturated steam line Y2.

In FIG. 5, a solid line indicated by R (a to b to c to d) indicates transition of the state of the refrigerant R in the heat pump cycle in a proper state.

The gas refrigerant R sucked in the superheated steam state into the compressor 11 is adiabatically compressed in the compressor 11 to turn into the high-temperature high-pressure gas refrigerant R in the superheated steam state (a to b), and thereafter, is condensed/supercooled in the condenser 12 to turn into the liquid refrigerant R in the supercooled liquid state (b to c). Thereafter, the refrigerant R is adiabatically expanded by the expansion valve 13 to turn into the refrigerant R in the wet steam state (c to d). Then, the refrigerant R in the wet steam state is evaporated/warmed in the evaporator 14 to turn into the gas refrigerant R in the superheated steam state (d to a). The refrigerant R circulates in such a cycle. Note that as detailed description of the course of (b to c) in FIG. 5, the condenser 12 releases latent heat and sensible heat of the gas refrigerant R to change the gas refrigerant R into the liquid refrigerant R, and supercools the liquid refrigerant R.

In a case where the target tapping temperature described herein is a temperature lower than the lower limit indicated by the settable range A, the difference in the temperature of the supply water W1 between the inlet side and the outlet side of the condenser 12 decreases, and for this reason, there is a probability that the refrigerant R is not sufficiently condensed/supercooled in the condenser 12 (b to c′). As a result, the position of “c′” indicating the state of the refrigerant Rafter passage through the condenser 12 is shifted to the right side as compared to that in the proper case. That is, supercooling is insufficient for the refrigerant R in the state of “c′.” Moreover, there is also a probability that the state of the liquid refrigerant R is not sufficiently brought. In this case, operation is not always performed in a proper heat pump cycle.

However, in the present embodiment, the lower limit is the value obtained by addition of the predetermined value to the temperature sensed by the second supply water temperature sensor 26. Thus, the system is controlled such that the difference in the temperature of the supply water W1 between the inlet side and the outlet side of the condenser 12 becomes greater than at least the predetermined value, and therefore, the above-described problem is not caused. That is, operation can be performed in the heat pump cycle in the proper state.

The target tapping temperature setting unit 122 sets the target tapping temperature within the above-described target tapping temperature settable range according to the temperature sensed by the second supply water temperature sensor 26. For example, an optional target tapping temperature can be set within the settable range A based on, e.g., a request from the hot water demand location.

That is, the target tapping temperature setting unit 122 can acquire the temperature sensed by the second supply water temperature sensor 26, and as the lower limit, can take the value obtained by addition of the predetermined value to the acquired temperature sensed by the second supply water temperature sensor 26 and increasing as the temperature sensed by the second supply water temperature sensor 26 increases to set the target tapping temperature. With this configuration, operation can be performed in the heat pump cycle in the proper state, and the target tapping temperature settable range can be broadened.

Note that a form in which a value obtained by addition of a preset value to the temperature sensed by the second supply water temperature sensor 26 is automatically set as the target tapping temperature may be employed.

The supply water flow rate control unit 123 controls the supply water flow rate adjustment section such that the temperature sensed by the tapping temperature sensor 27 reaches the target tapping temperature (the value set by the target tapping temperature setting unit 122), thereby adjusting the flow rate of the supply water W1.

For example, as specific control, the feedback control of taking, as a feedback value, the tapping temperature sensed in real time by the tapping temperature sensor 27 to adjust the drive frequency of the water supply pump 21 or the reflux pump 31 such that the tapping temperature converges to the target tapping temperature is preferably employed. For the feedback control, an arithmetic operation amount algorithm for proportional control (P control) or a combination of integral control (I control) and/or derivative control (D control) with the proportional control can be employed.

Note that the inverter-controllable water supply pump 21 forms the supply water flow rate adjustment section in the later-described once-through water passage mode, and the inverter-controllable reflux pump 31 forms the supply water flow rate adjustment section in the circulation water passage mode.

Note that the supply water flow rate adjustment section may be formed in other forms. For example, in a case where the water supply pump 21 and the reflux pump 31 are pumps configured such that only ON-OFF control is allowed, a proportional-controllable flow rate adjustment valve may be provided on the downstream side of each pump, and these valves may be provided as the supply water flow rate adjustment section. Alternatively, a proportional-controllable flow rate adjustment valve may be provided on the downstream side of the joint portion between the water supply line L1 and the reflux line L2, and may be provided as the supply water flow rate adjustment section.

As a configuration substituted for the water supply pump 21 and the reflux pump 31, an inverter-controllable pump may be provided on the downstream side of the joint portion between the water supply line L1 and the reflux line L2 after on-off valves have been provided on the water supply line L1 and the reflux line L2 or after a three-way valve has been provided at the joint portion between the water supply line L1 and the reflux line L2, and may be provided as the supply water flow rate adjustment section.

As described above, a proper target tapping temperature is set according to the temperature of the supply water W1 before the supply water W1 flows into the condenser 12, and therefore, occurrence of insufficient supercooling, an excessive supply water flow rate and the like in the condenser 12 can be prevented.

Further, the lower limit of the settable target tapping temperature range is set according to the temperature of the supply water W1 before the supply water W1 flows into the condenser 12, and therefore, insufficient supercooling in the condenser 12 can be reliably prevented, and the heat recovery amount in the evaporator 14 can be stabilized. Moreover, an excessive flow rate of the supply water W1 can be prevented, and degradation due to an overload of the water supply pump 21 or the like can be reduced.

Note that in the present embodiment, the temperature sensed by the second supply water temperature sensor 26 is used for setting the target tapping temperature, but the first supply water temperature sensor 24 may be used as a supply water temperature sensor configured to indirectly detect the temperature (the pre-condenser-inflow supply water temperature) of the supply water W1 before the supply water W1 flows into the condenser 12. Note that for more stable control, the temperature of the supply water W1 right before the supply water W1 flows into the condenser 12 is preferably measured using the second supply water temperature sensor 26.

As described so far, the supply-water warming system 1 of the present embodiment causes the heat source water W5 to flow in the heat recovery heat exchanger 40 and the evaporator 14 in this order. Moreover, the supply-water warming system 1 of the present embodiment includes the refrigerant flow rate adjustment section controlled based on the superheat degree of the gas refrigerant R flowing into the compressor 11 and configured to adjust the refrigerant flow rate. Further, the supply-water warming system 1 of the present embodiment includes the supply water flow rate adjustment section controlled based on the tapping temperature of the supply water W1 flowing out of the condenser 12 and configured to adjust the supply water flow rate. In addition, the control unit 100 includes the refrigerant flow rate control unit 113 configured to control the refrigerant flow rate adjustment section and the supply water flow rate control unit 123 configured to control the supply water flow rate adjustment section.

The heat source water W5 first flows in the heat recovery heat exchanger 40, and therefore, the heat output of the heat recovery heat exchanger 40 increases and the preheating amount of the supply water W1 increases. Note that as the heat source water temperature increases, the effect for increasing the heat output increases. As the heat recovery amount of the heat recovery heat exchanger 40 increases, the heat recovery amount of the heat pump circuit 10 can be relatively decreased. That is, in the case of obtaining the same system heat output as that in a case where the heat source water W5 flows in the evaporator 14 and the heat recovery heat exchanger 40 in this order, the output of the compressor is decreased so that the power consumption of the heat pump circuit 10 can be reduced.

In this case, the heat source water W5 first flows in the heat recovery heat exchanger 40, and the temperature of the heat source water W5 flowing into the evaporator 14 decreases accordingly. By further control addition, i.e., the multiplexing effect of a combination of adjustment of the refrigerant flow rate based on the superheat degree and adjustment of the supply water flow rate based on the tapping temperature, such as the multiplexing effect of an increase in heat input of the evaporator 14 by adjustment of the refrigerant flow rate according to a low superheat degree setting and a further increase in the heat output of the heat recovery heat exchanger 40 and an increase in heat output of the evaporator 14 by adjustment of the supply water flow rate according to a low tapping temperature setting, the COP of the system can be significantly increased in the configuration in which the heat source water W5 first flows in the heat recovery heat exchanger 40.

The water passage mode switching control unit 130 performs the water passage mode switching control of switching the water passage mode among the once-through water passage mode, the circulation water passage mode, and the water passage stop mode. More specifically, the water passage mode switching control unit 130 controls the water supply pump 21 and the reflux pump 31 as the water passage mode switching section, thereby performing the control of switching the water passage mode among the once-through water passage mode in which the water passes through the condenser 12 without the hot water W2 flowing in the reflux line L2, the circulation water passage mode in which the water passes through the condenser 12 while the hot water W2 is flowing in the reflux line L2, and the water passage stop mode in which the water passage to the condenser 12 is stopped.

Note that in the once-through water passage mode, drive of the reflux pump 31 is stopped while the water supply pump 21 is driven, and the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10 are driven. In the circulation water passage mode, drive of the water supply pump 21 is stopped while the reflux pump 31 is driven, and the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10 are driven. In the water passage stop mode, drive of the water supply pump 21 and the reflux pump 31 is stopped, and drive of the compressor 11 of the heat pump circuit 10 is also stopped. Moreover, drive of the heat source supply pump 53 is also preferably stopped.

Note that in the present embodiment, the water supply pump 21 and the reflux pump 31 form the water passage mode switching section, but the water passage mode switching section may be formed in other forms. For example, a three-way valve provided at the joint portion between the water supply line L1 and the reflux line L2 and a water supply pump provided on the downstream side of the joint portion between the water supply line L1 and the reflux line L2 can form the water passage mode switching section. In this case, the water passage mode is switched by switching of the three-way valve and ON/OFF of the water supply pump.

As described above, operation in the circulation water passage mode can be performed in addition to the once-through water passage mode, and therefore, circulation warming for the hot water tank 60 is performed as necessary so that a stored hot water temperature can be maintained. Moreover, it is configured such that in the circulation water passage mode, the reflux line L2 is used to cause the water stored in the hot water tank 60 to flow into the heat recovery heat exchanger 40. Thus, in a case where the temperature of the heat source water W5 is higher than the temperature of the hot water W2 stored in the hot water tank 60, the hot water W2 flowing as the supply water W1 is warmed not only by the condenser 12, but also is warmed by the heat recovery heat exchanger 40 before the condenser 12. Thus, warming is efficiently performed.

The water passage mode switching control unit 130 described herein can perform water supply control for the hot water tank 60, and can also perform the water passage mode switching control based on the temperature of the hot water W2 in the hot water tank 60.

Specifically, the water passage mode switching control unit 130 controls the water passage mode switching section to execute the once-through water passage mode in a case where a new water supply is executed for the joint portion of the reflux line L2, controls the water passage mode switching section to execute the circulation water passage mode in a case where the new water supply to the joint portion is stopped and the temperature sensed by the hot water temperature sensor 61 falls below a predetermined set temperature, and controls the water passage mode switching section to execute the water passage stop mode in a case where the new water supply to the joint portion is stopped and the temperature sensed by the hot water temperature sensor 61 exceeds the predetermined set temperature.

The water passage mode switching control will be described in detail with reference to a state transition chart illustrated in FIG. 6A.

The water passage mode switching control unit 130 monitors, during execution of each water passage mode, the water level of the hot water W2 in the hot water tank 60 by the water level detection unit 62, and monitors the temperature of the hot water W2 in the hot water tank 60 by the hot water temperature sensor 61. During execution of the water passage stop mode, in a case where the water level exceeds the position of the electrode rod 622 detected by the water level detection unit 62 and the temperature sensed by the hot water temperature sensor 61 exceeds a first set temperature (e.g., a temperature lower than the target tapping temperature by 2 to 3° C.), the water passage mode switching control unit 130 continues the water passage stop mode.

<Event E1>

During execution of the water passage stop mode, in a case where the water level in the hot water tank 60 has decreased and has fallen below the position of the electrode rod 622 detected by the water level detection unit 62, the water passage mode switching control unit 130 drives the water supply pump 21 while the reflux pump 31 is kept stopped. By drive of the water supply pump 21, a new supply of the makeup water W to the joint portion of the reflux line L2 is executed, and therefore, the water passage mode switching control unit 130 drives the heat source supply pump 53 and the compressor 11 such that the water passage mode transitions to the once-through water passage mode. In the once-through water passage mode, the hot water W2 adjusted to a predetermined target tapping temperature is supplied to the hot water tank 60.

<Event E2>

During execution of the once-through water passage mode, in a case where the water level in the hot water tank 60 has increased and has exceeded the position of the electrode rod 621 detected by the water level detection unit 62, the water passage mode switching control unit 130 stops the water supply pump 21 while the reflux pump 31 is kept stopped. By stop of the water supply pump 21, the new supply of the makeup water W to the joint portion of the reflux line L2 is stopped, and therefore, the water passage mode switching control unit 130 stops the heat source supply pump 53 and the compressor 11 such that the water passage mode transitions to the water passage stop mode. In the water passage stop mode, a supply of the hot water W2 to the hot water tank 60 is stopped.

<Event E3>

During execution of the water passage stop mode, in a case where the temperature sensed by the hot water temperature sensor 61 has fallen the set temperature, the reflux pump 31 is driven while the water supply pump 21 is kept stopped. By drive of the reflux pump 31, circulation of the stored water is executed in a state in which the new supply of the makeup water W to the joint portion of the reflux line L2 is stopped, and therefore, the water passage mode switching control unit 130 drives the heat source supply pump 53 and the compressor 11 such that the water passage mode transitions to the circulation water passage mode. In the circulation water passage mode, the hot water W2 rewarmed to the predetermined target tapping temperature is supplied to the hot water tank 60.

<Event E4>

During execution of the circulation water passage mode, in a case where the temperature sensed by the hot water temperature sensor 61 has exceeded the set temperature, the water passage mode switching control unit 130 stops the reflux pump 31 while the water supply pump 21 is kept stopped. Then, the heat source supply pump 53 and the compressor 11 are stopped such that the water passage mode transitions to the water passage stop mode. In the water passage stop mode, circulation of the hot water W2 to the hot water tank 60 is stopped.

<Event E5>

During execution of the circulation water passage mode, in a case where the water level in the hot water tank 60 has decreased and has fallen below the position of the electrode rod 622 detected by the water level detection unit 62, the water passage mode switching control unit 130 stops the reflux pump 31, and drives the water supply pump 21. By drive of the water supply pump 21, a new supply of the makeup water W to the joint portion of the reflux line L2 is executed, and therefore, the water passage mode switching control unit 130 keeps driving the heat source supply pump 53 and the compressor 11 such that the water passage mode transitions to the once-through water passage mode. In the once-through water passage mode, the hot water W2 adjusted to the predetermined target tapping temperature is supplied to the hot water tank 60.

Note that in the present embodiment, transition from the once-through water passage mode to the circulation water passage mode is not performed. This is because the water passage mode transitions to the once-through water passage mode when hot water demand is high, and therefore, a priority is placed on a supply of the makeup water W to the hot water tank 60 to quickly recover the water level. Moreover, the tapping temperature in the once-through water passage mode is higher than the stored hot water temperature in the hot water tank 60, and therefore, the stored hot water temperature can be increased in a short time.

Note that the set temperature for determining continuation of the water passage stop mode and the set temperature for determining transition from the water passage stop mode to the circulation water passage mode may be the same temperature or different temperatures. In the case of the different temperatures, the latter set temperature is a temperature lower than the former set temperature.

Note that for performing the above-described water passage mode switching control, determination on whether or not, e.g., a new supply of the makeup water W to the joint portion of the reflux line L2 is executed may be performed based on a drive state (a drive command signal or a drive feedback signal) of the water supply pump 21.

Alternatively, a not-shown flow rate sensor may be arranged on the water supply line L1 on the upstream side with respect to the joint portion of the reflux line L2, and determination may be performed based on a detection result of this flow rate sensor.

According to the mode switching control according to the state transition chart of FIG. 6A, when there is sufficient hot water demand and a supply of the makeup water W is necessary, operation can be performed in the once-through water passage mode with the maximum system COP. When there is low hot water demand and a supply of the makeup water W is not necessary, the temperature of the stored water can be increased in the circulation water passage mode upon a decrease in the temperature of the stored water in the hot water tank 60. When there is low hot water demand and a supply of the makeup water W is not necessary, if there is substantially no decrease in the temperature of the stored water in the hot water tank 60, operation can stand by in the water passage stop mode.

With the above-described configuration, the hot water W2 at the set temperature or higher can be constantly ensured in the hot water tank 60. Moreover, the circulation water passage mode is executed only upon a decrease in the temperature of the stored water in the hot water tank 60, and therefore, there is no unnecessary power consumption due to excessive water circulation.

The preheating mode switching control unit 140 performs the preheating mode switching control of switching a preheating mode between a supply water preheating mode and a preheating stop mode. More specifically, the preheating mode switching control unit 140 controls the three-way valve 25 as the preheating mode switching section to perform the control of switching the preheating mode between the supply water preheating mode in which the supply water W1 and the heat source water W5 simultaneously flow in the heat recovery heat exchanger 40 and the preheating stop mode in which the supply water W1 flows in the bypass line L3.

Note that in the present embodiment, the three-way valve 25 forms the preheating mode switching section, but the preheating mode switching section may be formed in other forms. For example, two-way valves may be each provided on the upstream side of the joint portion of the bypass line L3 on the water supply line L1 and on the bypass line L3, and may form the preheating mode switching section.

Note that the bypass line is not limited to one causing the supply water W1 to bypass the heat recovery heat exchanger 40, and may be one causing the heat source water W5 to bypass the heat recovery heat exchanger 40. In this case, in the preheating stop mode, the heat source water W5 flows in the bypass line.

That is, it may only be required that one or two bypass lines configured to cause the supply water W1 to bypass the heat recovery heat exchanger 40 and/or cause the heat source water W5 to bypass the heat recovery heat exchanger 40 are provided and the preheating mode switching section is in such a form that the preheating mode is switched between the supply water preheating mode in which the supply water W1 and the heat source water W5 simultaneously flow in the heat recovery heat exchanger 40 and the preheating stop mode in which at least one of the supply water W1 or the heat source water W5 flows in the bypass line.

With this configuration, the heat recovery heat exchanger 40 can be selectively utilized according to a situation.

The preheating mode switching control unit 140 described herein can acquire a first sensed temperature (a pre-heat-exchanger-inflow supply water temperature) obtained by the first supply water temperature sensor 24 (the pre-heat-exchanger-inflow supply water temperature sensor 24) configured to sense the temperature of the supply water W1 before the supply water W1 flows into the heat recovery heat exchanger 40 and a second sensed temperature (a pre-heat-exchanger-inflow heat source temperature) obtained by the first heat source temperature sensor 54 (the pre-heat-exchanger-inflow heat source temperature sensor 54) configured to sense the temperature of the heat source water W5 before the heat source water W5 flows into the heat recovery heat exchanger 40, thereby performing the preheating mode switching control based on the first sensed temperature and the second sensed temperature.

Specifically, the preheating mode switching control unit 140 compares the first sensed temperature obtained by the first supply water temperature sensor 24 and the second sensed temperature obtained by the first heat source temperature sensor 54 with each other, thereby controlling the preheating mode switching section to execute the supply water preheating mode in a case where the first sensed temperature falls below the second sensed temperature and controlling the preheating mode switching section to execute the preheating stop mode in a case where the first sensed temperature exceeds the second sensed temperature.

Such automatic preheating mode switching according to the supply water temperature and the heat source water temperature can maximize the system COP.

Note that the preheating mode switching control unit 140 can switch the preheating mode switching section between the preheating modes when the water passage mode is at least the circulation water passage mode. In this case, the preheating mode switching control unit 140 may set the preheating mode switching section to the supply water preheating mode when the water passage mode is the once-through water passage mode, and may set the preheating mode switching section to the preheating stop mode when the water passage mode is the water passage stop mode.

In this manner, in, e.g., the once-through water passage mode using, as the supply water W1, the makeup water W often having a relatively-low temperature, the heat recovery heat exchanger is actively utilized. On the other hand, in the circulation water passage mode using, as the supply water W1, the stored water of the hot water tank 60 often having a relatively-high temperature, the heat recovery heat exchanger can be selectively utilized according to a temperature relationship between the supply water W1 and the heat source water W5.

Note that the preheating mode switching control unit 140 may be configured to switch the preheating mode switching section between the preheating modes when the water passage mode is the circulation water passage mode or the once-through water passage mode so that efficient warming can be performed even under various makeup water temperature and heat source water temperature situations.

The signal input unit 150 includes a first signal input unit 151 configured to receive a water passage mode specifying signal for specifying any of the once-through water passage mode, the circulation water passage mode, and the water passage stop mode.

The water passage mode switching control unit 130 controls, according to the water passage mode specifying signal input to the first signal input unit 151, the water passage mode switching section to execute the once-through t water passage mode, the circulation water passage mode, or the water passage stop mode. Then, the water passage mode switching control unit 130 controls, for example, the water supply pump 21 upon execution of the circulation water passage mode or the water passage stop mode to stop a new water supply to the joint portion of the reflux line L2.

In this manner, operation can be, utilizing an external signal indicating the presence of the makeup water, performed in the once-through water passage mode with the maximum system COP, for example. Moreover, utilizing an external signal indicating the absence of the makeup water, warming of the stored water can be performed in the circulation water passage mode.

The signal input unit 150 also includes a second signal input unit 152 configured to receive a preheating mode specifying signal for specifying any of the supply water preheating mode and the preheating stop mode.

The preheating mode switching control unit 140 controls, according to the preheating mode specifying signal input to the second signal input unit 152, the preheating mode switching section to execute the supply water preheating mode or the preheating stop mode.

In this manner, the system COP can be maximized by passive heating mode switching according to an external signal.

The storage unit 160 stores various types of information necessary for the control, such as various thresholds.

Next, one example of the flow of control by the control unit 100 of the present embodiment will be described.

FIG. 6B is a flowchart of one example of the flow of target superheat degree setting processing by the target superheat degree setting unit 111 of the control unit 100.

First, when the system is started, the target superheat degree setting unit 111 sets, at a step S1, the target superheat degree to a high temperature such as 10° C.

Next, at a step S2, it is determined whether or not the temperature sensed by the second heat source temperature sensor 55 is stable and is equal to or lower than a predetermined heat source temperature threshold (e.g., 60° C.). In a case where it is determined that the temperature sensed by the second heat source temperature sensor 55 is stable (ΔT≤ΔT0, see FIG. 3) and is equal to or lower than the predetermined heat source temperature threshold (the step S2: YES), the target superheat degree is set to a small value such as 5° C. at a step S3. On the other hand, in a case where it is determined that the temperature sensed by the second heat source temperature sensor 55 is not stable or exceeds the predetermined heat source temperature threshold (the step S2: NO), the processing returns to the step S1 to continuously maintain the target superheat degree at 10° C.

After the target superheat degree has been set to 5° C. at the step S3, it is, at a step S4, determined whether or not the fluctuation in the temperature sensed by the second heat source temperature sensor 55 is great or exceeds the predetermined heat source temperature threshold, for example. In a case where it is determined that the fluctuation in the temperature sensed by the second heat source temperature sensor 55 is great (ΔT>ΔT0, see FIG. 3) or exceeds the predetermined heat source temperature threshold (the step S4: YES), the target superheat degree is increased and set to, e.g., 10° C. at a step S5. On the other hand, in a case where it is determined that the fluctuation in the temperature sensed by the second heat source temperature sensor 55 is not great and is equal to or lower than the predetermined heat source temperature threshold (the step S4: NO), the processing returns to the step S3 to continuously maintain the target superheat degree at 5° C.

In this manner, even in a case where the situation where the temperature of the heat source water W5 as the heat source fluid rapidly changes has been confirmed, the heat pump circuit 10 can be stably driven.

Next, the preheating mode switching control will be described. Note that the water passage mode switching control is as described above (see FIG. 6A).

FIG. 6C is a flowchart of one example of the flow of the preheating mode switching control of switching the preheating mode between the supply water preheating mode and the preheating stop mode by the preheating mode switching control unit 140 of the control unit 100. In this example, the preheating mode switching control unit 140 performs the preheating mode switching control based on detection results of the first sensed temperature (the pre-heat-exchanger-inflow supply water temperature) obtained by the first supply water temperature sensor 24 (the pre-heat-exchanger-inflow supply water temperature sensor) and the second sensed temperature (the pre-heat-exchanger-inflow heat source temperature) obtained by the first heat source temperature sensor 54 (the pre-heat-exchanger-inflow heat source temperature sensor).

At a step S11, the preheating mode switching control unit 140 determines whether or not the circulation water passage mode is executed. Ina case where the circulation water passage mode is executed (the step S21: YES), the detection results of the first sensed temperature obtained by the first supply water temperature sensor 24 and the second sensed temperature obtained by the first heat source temperature sensor 54 are compared with each other at a step S12. In a case where the first sensed temperature falls below the second sensed temperature (the step S12: YES), the supply water preheating mode is executed at a step S13. On the other hand, in a case where the first sensed temperature does not fall below the second sensed temperature (the step S12: NO), the preheating stop mode is executed at a step S14.

Note that the control of determining whether or not the once-through water passage mode or the circulation water passage mode is executed and causing the processing to transition to the step S12 in a case where the once-through water passage mode or the circulation water passage mode is executed may be employed at the step S11.

FIG. 7 is a schematic diagram of a variation of the supply-water warming system 1 of the first embodiment.

The condenser 12 of the heat pump circuit 10 in the present embodiment takes on the function of condensing and supercooling the refrigerant R. However, as in the present variation, the condenser of the heat pump circuit 10 may be divided into a condenser 12A mainly taking on the function of condensing the refrigerant R and a supercooler 12B mainly taking on the function of supercooling the refrigerant R. In this case, the refrigerant R in the heat pump circuit 10 preferably releases latent heat in the condenser 12A, and releases sensible heat in the supercooler 12B. That is, the gas refrigerant R is condensed into the liquid refrigerant R in the condenser 12A, and such liquid refrigerant R is supplied to the supercooler 12B and is further cooled (supercooled) in the supercooler 12B.

The supercooler 12B is an indirect heat exchanger configured to perform heat exchange between the supply water W1 sent to the condenser 12A and the refrigerant R flowing from the condenser 12A to the expansion valve 13. The supercooler 12B can supercool the refrigerant R flowing from the condenser 12A to the expansion valve 13 by means of the supply water W1 to the condenser 12A, and can warm the supply water W1 to the condenser 12A by means of the refrigerant R flowing from the condenser 12A to the expansion valve 13.

In this manner, the heat exchanger is divided into one for condensing the refrigerant R and one for supercooling the refrigerant R. Thus, the heat exchanger can be easily designed, and cost reduction can be realized. Moreover, a general-purpose heat exchanger can be also utilized.

Note that in the present variation, the second supply water temperature sensor 26 as the supply water temperature sensor configured to sense the temperature of the supply water W1 before the supply water W1 flows into the condenser 12 of the heat pump circuit 10 is preferably arranged on the upstream side of the supercooler 12B.

Note that in a case where a decrease in the temperature of the hot water W2 in the hot water tank 60 is acceptable to a certain extent, such as a case where the hot water demand location is the steam boiler, a not-shown makeup water line for directly supplying the water from the makeup water tank 70 to the hot water tank 60 without the heat recovery heat exchanger 40 and the heat pump circuit 10 may be provided. In this case, e.g., when the water level of the hot water W2 in the hot water tank 60 becomes lower than a detection position of an electrode rod longer than the electrode rod 622, a makeup water pump provided on the makeup water line is driven so that the makeup water W can be directly supplied from the makeup water tank 70 to the hot water tank 60.

Note that in the present embodiment, the heat source water W5 is used as the heat source fluid for the heat pump circuit 10, but the heat source fluid is not limited to the heat source water W5. Various types of fluid such as air and exhaust gas can be used. The heat source fluid is preferably fluid decreasing in temperature while providing heat (sensible heat) to the supply water W1 in the heat recovery heat exchanger 40 and decreasing in temperature while providing heat (sensible heat) to the refrigerant R of the heat pump circuit 10 in the evaporator 14.

Note that the drive source of the compressor 11 of the heat pump circuit 10 is not limited to the electric motor. For example, the compressor 11 may be driven by a steam motor configured to generate power by means of steam, or may be driven by a gas engine. In this case, the output of the compressor 11 may be adjusted by, e.g., adjustment of the amount of steam supplied to the steam motor or the amount of gas supplied to the gas engine, and in this manner, the refrigerant flow rate may be adjusted.

According to the supply-water warming system 1 of the first embodiment as described above, advantageous effects as indicated by (1A) to (11A) below are provided.

(1A) The supply-water warming system 1 of the present embodiment includes the steam compression heat pump circuit 10 configured such that the compressor 11, the condenser 12, the expansion valve 13, and the evaporator 14 are connected in the annular shape through the refrigerant circulation line L9 and configured to take out the warmth in the condenser 12 by drive of the compressor 11, the heat recovery heat exchanger 40, the heat source fluid line L5 in which the heat source fluid flows in the heat recovery heat exchanger 40 and the evaporator 14 in this order, the water supply line L1 in which the supply water W1 flows in the heat recovery heat exchanger 40 and the condenser 12 in this order, the refrigerant flow rate adjustment section controlled based on the superheat degree of the gas refrigerant R flowing into the compressor 11 and configured to adjust the refrigerant flow rate, the supply water flow rate adjustment section controlled based on the tapping temperature of the supply water W1 flowing out of the condenser 12 and configured to adjust the supply water flow rate, and the control section configured to control the refrigerant flow rate adjustment section and the supply water flow rate adjustment section.

The heat source water W5 as the heat source fluid first flows in the heat recovery heat exchanger 40 as described above, and therefore, the heat output of the heat recovery heat exchanger 40 is increased and the preheating amount of the supply water W1 is increased. As the heat source water temperature increases, the effect of increasing the heat output increases. The heat recovery amount of the heat recovery heat exchanger 40 increases, and therefore, the heat recovery amount of the heat pump circuit 10 can be relatively decreased. In the case of obtaining the same system heat output as that in a case where the heat source water W5 flows in the evaporator 14 and the heat recovery heat exchanger 40 in this order, the output of the compressor 11 is decreased so that the power consumption of the heat pump circuit 10 can be reduced.

In this case, the heat source water W5 first flows in the heat recovery heat exchanger 40, and the temperature of the heat source water W5 flowing into the evaporator 14 decreases accordingly. By further control addition, i.e., the multiplexing effect of the combination of adjustment of the refrigerant flow rate based on the superheat degree and adjustment of the supply water flow rate based on the tapping temperature, such as the multiplexing effect of an increase in the heat input of the evaporator 14 by adjustment of the refrigerant flow rate according to the low superheat degree setting and a further increase in the heat output of the heat recovery heat exchanger 40 and an increase in the heat output of the evaporator 14 by adjustment of the supply water flow rate according to the low tapping temperature setting, the COP of the system can be significantly increased in the configuration in which the heat source water W5 first flows in the heat recovery heat exchanger 40.

(2A) The heat source fluid line L5 of the supply-water warming system 1 of the present embodiment has the connection configuration in which after the heat source fluid and the supply water W1 have exchanged heat in the counter flow in the heat recovery heat exchanger 40, the heat source fluid and the liquid refrigerant R exchange heat in the counter flow in the evaporator 14.

As described above, the heat source water W5 flows in the heat recovery heat exchanger 40 and the evaporator 14 in this order, and flows in the counter flow with respect to the flow direction of the supply water W1 in each of the heat recovery heat exchanger 40 and the evaporator 14. Thus, the heat recovery amount can be maximized.

(3A) The supply-water warming system 1 of the present embodiment further includes the suction temperature sensor 17 configured to sense the suction temperature of the gas refrigerant R flowing into the compressor 11, the steam pressure sensor 18 configured to sense the steam pressure of the gas refrigerant R flowing out of the evaporator 14, and the tapping temperature sensor 27 configured to sense the tapping temperature of the supply water W1 flowing out of the condenser 12. The control section obtains the evaporation temperature of the liquid refrigerant R from the pressure sensed by the steam pressure sensor 18, calculates the superheat degree of the gas refrigerant R by subtracting the evaporation temperature from the temperature sensed by the suction temperature sensor 17, and controls the refrigerant flow rate adjustment section such that the calculated superheat degree reaches the target superheat degree. The control section controls the supply water flow rate adjustment section such that the temperature sensed by the tapping temperature sensor 27 reaches the target tapping temperature.

As described above, the superheat degree of the gas refrigerant R is accurately calculated, and such a value is held constant. Thus, the heat output of the condenser 12 to the supply water W1 after preheating is stabilized. Consequently, fluctuation in the flow rate of the hot water is reduced. Moreover, the supply water flow rate is, for example, properly increased by the set value of the target tapping temperature, and such a flow rate is held within a certain range. Thus, high heat output can be maintained.

(4A) The supply-water warming system 1 of the present embodiment further includes the heat source temperature sensor configured to sense the temperature of the heat source fluid before the heat source fluid flows into the evaporator 14. The control section sets the target superheat degree according to the temperature sensed by the heat source temperature sensor.

As described above, a proper target superheat degree is set according to the temperature of the heat source fluid, and therefore, damage of the compressor 11 due to liquid compression can be prevented while the heat recovery amount in the evaporator 14 can be increased.

For example, in the case of a low heat source water temperature, the target superheat degree is set low, and the refrigerant circulation flow rate increases accordingly. Thus, even with the low-temperature heat source water W5, the heat recovery amount can be increased. The lower limit of the target superheat degree is set to, e.g., 5° C. so that damage of the compressor 11 due to liquid compression can be prevented. Moreover, the upper limit of the target superheat degree is set to, e.g., 10° C. so that the refrigerant circulation flow rate can be maintained at the predetermined flow rate or higher and a decrease in the heat recovery amount can be prevented.

(5A) The control section of the supply-water warming system 1 of the present embodiment increases the target superheat degree in a case where it is determined that the fluctuation in the temperature sensed by the heat source temperature sensor is great.

With this configuration, even in a case where the situation where the temperature of the heat source fluid rapidly changes has been confirmed, the heat pump circuit 10 can be stably driven.

For example, even in a case where the temperature of the heat source fluid has rapidly decreased, the target superheat degree is set to a high value so that the refrigerant can be reliably vaporized in the evaporator 14. Thus, damage of the compressor 11 due to liquid compression can be prevented.

(6A) The control section of the supply-water warming system 1 of the present embodiment decreases the target superheat degree in a case where it is determined that the temperature sensed by the heat source temperature sensor is stable.

With this configuration, when the temperature of the heat source fluid is stable, the target superheat degree is set to a low value so that the refrigerant circulation flow rate can be increased and the heat recovery amount in the evaporator 14 can be increased.

(7A) The supply-water warming system 1 of the present embodiment further includes the supply water temperature sensor configured to sense the temperature of the supply water before the supply water flows into the condenser 12. The control section sets the target tapping temperature according to the temperature sensed by the supply water temperature sensor.

As described above, a proper target tapping temperature is set according to the temperature of the supply water, and therefore, occurrence of insufficient supercooling, an excessive supply water flow rate or the like in the condenser 12 can be prevented.

(8A) The supply-water warming system 1 of the present embodiment further includes the supply water temperature sensor configured to sense the temperature of the supply water before the supply water flows into the condenser 12. The target tapping temperature is settable to the value between the upper limit and the lower limit, and the lower limit is the value obtained by addition of the predetermined value to the temperature sensed by the supply water temperature sensor and increasing as the temperature sensed by the supply water temperature sensor increases.

As described above, the lower limit of the settable target tapping temperature range is set according to the temperature of the supply water, and therefore, insufficient supercooling in the condenser 12 can be reliably prevented, and the heat recovery amount in the evaporator 14 can be stabilized. Moreover, an excessive supply water flow rate can be prevented, and degradation due to the overload of the water supply pump 21 can be reduced.

(9A) The supply-water warming system 1 of the present embodiment further includes one or two bypass lines configured to cause the supply water W1 to bypass the heat recovery heat exchanger 40 and/or cause the heat source fluid to bypass the heat recovery heat exchanger 40, and the preheating mode switching section configured to switch the preheating mode between the supply water preheating mode in which the supply water W1 and the heat source fluid simultaneously flow in the heat recovery heat exchanger 40 and the preheating stop mode in which at least one of the supply water W1 or the heat source fluid flows in the one or two bypass lines.

With this configuration, the heat recovery heat exchanger 40 is bypassed under a condition where the effect of the heat recovery heat exchanger 40 cannot be achieved, and therefore, a pressure loss of the supply water W1 and/or the heat source water W5 can be reduced and the COP of the system including the water supply pump 21 and the heat source supply pump 53 can be improved.

(10A) The supply-water warming system 1 of the present embodiment further includes the pre-heat-exchanger-inflow supply water temperature sensor 24 configured to sense the temperature of the supply water W1 before the supply water W1 flows into the heat recovery heat exchanger 40, and the pre-heat-exchanger-inflow heat source temperature sensor 54 configured to sense the temperature of the heat source fluid before the heat source fluid flows into the heat recovery heat exchanger 40. The control section compares the first sensed temperature obtained by the pre-heat-exchanger-inflow supply water temperature sensor 24 and the second sensed temperature obtained by the pre-heat-exchanger-inflow heat source temperature sensor 54, controls the preheating mode switching section to execute the supply water preheating mode in a case where the first sensed temperature falls below the second sensed temperature, and controls the preheating mode switching section to execute the preheating stop mode in a case where the first sensed temperature exceeds the second sensed temperature.

Such automatic preheating mode switching according to the supply water temperature and the heat source water temperature can maximize the system COP.

(11A) The control section of the supply-water warming system 1 of the present embodiment includes the signal input unit 150 configured to receive the preheating mode specifying signal for specifying the type which is the supply water preheating mode or the preheating stop mode, and the preheating mode switching control unit 140 configured to control, according to the preheating mode specifying signal input to the signal input unit 150, the preheating mode switching section to execute the supply water preheating mode or the preheating stop mode.

Such passive preheating mode switching according to the external signal can maximize the system COP.

According to the supply-water warming system 1 of the first embodiment as described above, advantageous effects as indicated by (1B) to (8B) below are also provided.

(1B) The supply-water warming system 1 of the present embodiment includes the steam compression heat pump circuit 10 configured such that the compressor 11, the condenser 12, the expansion valve 13, and the evaporator 14 are connected in the annular shape through the refrigerant circulation line L9 and configured to take out the warmth in the condenser 12 by drive of the compressor 11, the heat recovery heat exchanger 40, the heat source fluid line L5 in which the heat source fluid flows in the heat recovery heat exchanger 40 and the evaporator 14, the water supply line L1 in which the supply water W1 flows in the heat recovery heat exchanger 40 and the condenser 12 in this order, the hot water tank 60 configured to store the hot water W2 generated in the condenser 12, the reflux line L2 in which the hot water W2 in the hot water tank 60 flows back to the upstream side with respect to the heat recovery heat exchanger 40, the water passage mode switching section configured to switch the water passage mode among the once-through water passage mode in which the water flows in the condenser 12 without the hot water W2 flowing in the reflux line L2, the circulation water passage mode in which the water flows in the condenser 12 while the hot water W2 is flowing in the reflux line L2, and the water passage stop mode in which water passage to the condenser 12 is stopped, and the control section configured to control the water passage mode switching section.

As described above, operation in the circulation water passage mode can be performed in addition to the once-through water passage mode, and therefore, circulation warming for the hot water tank 60 is performed as necessary so that the stored hot water temperature can be maintained. It is configured such that in the circulation water passage mode, the stored water flows into the front of the heat recovery heat exchanger 40. Thus, in the case of the stored water temperature<the heat source water temperature, efficient warming can be performed.

(2B) The supply-water warming system 1 of the present embodiment further includes one or two bypass lines configured to cause the supply water W1 to bypass the heat recovery heat exchanger 40 and/or cause the heat source fluid to bypass the heat recovery heat exchanger 40, and the preheating mode switching section configured to switch the preheating mode between the supply water preheating mode in which the supply water W1 and the heat source fluid simultaneously flow in the heat recovery heat exchanger 40 and the preheating stop mode in which at least one of the supply water W1 or the heat source fluid flows in the one or two bypass lines.

With this configuration, the heat recovery heat exchanger 40 can be selectively utilized according to a situation.

(3B) The control section of the supply-water warming system 1 of the present embodiment can switch the preheating mode switching section between the supply water preheating mode and the preheating stop mode at least in the circulation water passage mode.

With this configuration, the heat recovery heat exchanger 40 can be actively utilized in the once-through water passage mode, and can be selectively utilized in the circulation water passage mode, for example.

(4B) The heat source fluid line L5 of the supply-water warming system 1 of the present embodiment has the connection configuration in which the heat source fluid flows in the heat recovery heat exchanger 40 and the evaporator 14 in this order.

With this configuration, the heat source water W5 as the heat source fluid first flows in the heat recovery heat exchanger 40, and therefore, the preheating amount of the supply water W1 is increased. Thus, the heat output of the heat recovery heat exchanger 40 can be increased. As the heat source water temperature increases, the effect of increasing the heat output increases.

(5B) The supply-water warming system 1 of the present embodiment further includes the hot water temperature sensor 61 configured to sense the temperature of the hot water W2 in the hot water tank 60. The control section controls the water passage mode switching section to execute the once-through water passage mode in a case where a new water supply to the joint portion of the reflux line L2 is executed, controls the water passage mode switching section to execute the circulation water passage mode in a case where the new water supply to the joint portion is stopped and the temperature sensed by the hot water temperature sensor 61 falls below the set temperature, and controls the water passage mode switching section to execute the water passage stop mode in a case where the new water supply to the joint portion is stopped and the temperature sensed by the hot water temperature sensor 61 exceeds the set temperature.

With this configuration, when there is sufficient hot water demand and a supply of the makeup water W is necessary, operation can be performed in the once-through water passage mode with the maximum system COP. When there is low hot water demand and a supply of the makeup water W is not necessary, the temperature of the stored water can be increased in the circulation water passage mode upon a decrease in the temperature of the stored water in the hot water tank 60.

(6B) The supply-water warming system 1 of the present embodiment further includes the pre-heat-exchanger-inflow supply water temperature sensor 24 configured to sense the temperature of the supply water W1 before the supply water W1 flows into the heat recovery heat exchanger 40, and the pre-heat-exchanger-inflow heat source temperature sensor 54 configured to sense the temperature of the heat source fluid before the heat source fluid flows into the heat recovery heat exchanger 40. The control section compares the first sensed temperature obtained by the pre-heat-exchanger-inflow supply water temperature sensor 24 and the second sensed temperature obtained by the pre-heat-exchanger-inflow heat source temperature sensor 54, controls the preheating mode switching section to execute the supply water preheating mode in a case where the first sensed temperature falls below the second sensed temperature, and controls the preheating mode switching section to execute the preheating stop mode in a case where the first sensed temperature exceeds the second sensed temperature.

Such automatic preheating mode switching according to the supply water temperature and the heat source water temperature can maximize the system COP.

(7B) The control section of the supply-water warming system 1 of the present embodiment includes the first signal input unit 151 configured to receive the water passage mode specifying signal for specifying any of the once-through water passage mode, the circulation water passage mode, and the water passage stop mode, and the water passage mode switching control unit 130 configured to control, according to the water passage mode specifying signal input to the first signal input unit 151, the water passage mode switching section to execute the once-through water passage mode, the circulation water passage mode, or the water passage stop mode. The water passage mode switching control unit 130 stops a new water supply to the joint portion of the reflux line L2 upon execution of the circulation water passage mode or the water passage stop mode.

With this configuration, operation can be, utilizing the external signal indicating the presence of the makeup water, performed in the once-through water passage mode with the maximum system COP, for example. Moreover, utilizing the external signal indicating the absence of the makeup water, warming of the stored water can be performed in the circulation mode.

(8B) The control section of the supply-water warming system 1 of the present embodiment includes the second signal input unit 152 configured to receive the preheating mode specifying signal for specifying any of the supply water preheating mode and the preheating stop mode, and the preheating mode switching control unit 140 configured to control, according to the preheating mode specifying signal input to the second signal input unit 152, the preheating mode switching section to execute the supply water preheating mode or the preheating stop mode.

With this configuration, e.g., passive heating mode switching according to the external signal is allowed, and the system COP can be maximized.

According to the supply-water warming system 1 of the first embodiment as described above, advantageous effects as indicated by (1C) to (7C) below are also provided.

(1C) The supply-water warming system 1 of the present embodiment includes the steam compression heat pump circuit 10 configured such that the compressor 11, the condenser 12, the expansion valve 13, and the evaporator 14 are connected in the annular shape through the refrigerant circulation line L9 and configured to take out the warmth in the condenser 12 by drive of the compressor 11, the refrigerant flow rate adjustment section configured to adjust the flow rate of the refrigerant R flowing in the heat pump circuit 10, the heat source temperature sensor configured to sense the temperature of the heat source fluid exchanging heat with the refrigerant R in the evaporator 14, and the control section configured to control the refrigerant flow rate adjustment section. The control section sets the target superheat degree according to the temperature sensed by the heat source temperature sensor, and controls the refrigerant flow rate adjustment section such that the superheat degree of the refrigerant R flowing into the compressor 11 reaches the target superheat degree.

As described above, a proper target superheat degree is set according to the temperature of the heat source fluid, and therefore, damage of the compressor 11 due to liquid compression can be prevented while the heat recovery amount in the evaporator 14 can be increased.

For example, in the case of a low heat source water temperature, the target superheat degree is set low, and the refrigerant circulation flow rate increases accordingly. Thus, even with the low-temperature heat source water W5 as the heat source fluid, the heat recovery amount can be increased. The lower limit of the target superheat degree is set to, e.g., 5° C. so that damage of the compressor 11 due to liquid compression can be prevented. Moreover, the upper limit of the target superheat degree is set to, e.g., 10° C. so that the refrigerant circulation flow rate can be maintained at the predetermined flow rate or higher and a decrease in the heat recovery amount can be prevented.

(2C) The control section of the supply-water warming system 1 of the present embodiment increases the target superheat degree in a case where it is determined that the fluctuation in the temperature sensed by the heat source temperature sensor is great.

With this configuration, even in a case where the situation where the temperature of the heat source fluid rapidly changes has been confirmed, the heat pump circuit 10 can be stably driven.

For example, even in a case where the temperature of the heat source fluid has rapidly decreased, the target superheat degree is set to a high value so that the refrigerant can be reliably vaporized in the evaporator 14. Thus, damage of the compressor 11 due to liquid compression can be prevented.

(3C) The control section of the supply-water warming system 1 of the present embodiment decreases the target superheat degree in a case where it is determined that the temperature sensed by the heat source temperature sensor is stable.

With this configuration, when the temperature of the heat source fluid is stable, the target superheat degree is set to a low value so that the refrigerant circulation flow rate can be increased and the heat recovery amount in the evaporator 14 can be increased.

(4C) The supply-water warming system 1 of the present embodiment further includes the suction temperature sensor 17 configured to sense the suction temperature of the gas refrigerant R flowing into the compressor 11, and the steam pressure sensor 18 configured to sense the steam pressure of the gas refrigerant R flowing out of the evaporator 14. The control section obtains the evaporation temperature of the liquid refrigerant R from the pressure sensed by the steam pressure sensor 18, calculates the superheat degree of the gas refrigerant R by subtracting the evaporation temperature from the temperature sensed by the suction temperature sensor 17, and controls the refrigerant flow rate adjustment section such that the calculated superheat degree reaches the target superheat degree.

As described above, the superheat degree of the gas refrigerant R is accurately calculated, and such a value is held constant. Thus, the heat output of the condenser 12 to the supply water W1 after preheating is stabilized. Consequently, the fluctuation in the flow rate of the hot water is reduced.

(5C) The supply-water warming system 1 of the present embodiment further includes the supply water flow rate adjustment section configured to adjust the flow rate of the supply water flowing in the condenser 12, and the tapping temperature sensor 27 configured to sense the tapping temperature of the supply water W1 flowing out of the condenser 12. The control section controls the supply water flow rate adjustment section such that the temperature sensed by the tapping temperature sensor 27 reaches the target tapping temperature.

With this configuration, the supply water W1 can be constantly warmed to a desired temperature, and can be tapped.

(6C) The supply-water warming system 1 of the present embodiment further includes the supply water temperature sensor configured to sense the temperature of the supply water W1 before the supply water W1 flows into the condenser 12. The control section sets the target tapping temperature according to the temperature sensed by the supply water temperature sensor.

As described above, a proper target tapping temperature is set according to the temperature of the supply water W1, and therefore, occurrence of insufficient supercooling, an excessive supply water flow rate or the like in the condenser 12 can be prevented.

(7C) The supply-water warming system 1 of the present embodiment further includes the supply water temperature sensor configured to sense the temperature of the supply water W1 before the supply water W1 flows into the condenser 12. The target tapping temperature is settable to the value between the upper limit and the lower limit, and the lower limit is the value obtained by addition of the predetermined value to the temperature sensed by the supply water temperature sensor and increasing as the temperature sensed by the supply water temperature sensor increases.

As described above, the lower limit of the settable target tapping temperature range is set according to the temperature of the supply water, and therefore, insufficient supercooling in the condenser 12 can be reliably prevented, and the heat recovery amount in the evaporator 14 can be stabilized. Moreover, an excessive supply water flow rate can be prevented, and degradation due to the overload of the water supply pump 21 can be reduced.

The preferred embodiments of the supply-water warming system of the present invention have been described above, but the present invention is not limited to the above-described embodiments and changes can be made to the present invention as necessary.

Claims

1. A supply-water warming system comprising:

a steam compression heat pump circuit configured such that a compressor, a condenser, an expansion valve, and an evaporator are connected in an annular shape through a refrigerant circulation line and configured to take out warmth in the condenser by drive of the compressor;

a heat recovery heat exchanger;

a heat source fluid line in which heat source fluid flows in the heat recovery heat exchanger and the evaporator in this order;

a water supply line in which supply water flows in the heat recovery heat exchanger and the condenser in this order;

a refrigerant flow rate adjustment section controlled based on a superheat degree of gas refrigerant flowing into the compressor and configured to adjust a refrigerant flow rate;

a supply water flow rate adjustment section controlled based on a tapping temperature of the supply water flowing out of the condenser and configured to adjust a supply water flow rate; and

a control section configured to control the refrigerant flow rate adjustment section and the supply water flow rate adjustment section.

2. The supply-water warming system according to claim 1, wherein

the heat source fluid line has a connection configuration in which after the heat source fluid and the supply water have exchanged heat in a counter flow in the heat recovery heat exchanger, the heat source fluid and liquid refrigerant exchange heat in a counter flow in the evaporator.

3. The supply-water warming system according to claim 1, further comprising:

a suction temperature sensor configured to sense a suction temperature of the gas refrigerant flowing into the compressor;

a steam pressure sensor configured to sense a steam pressure of the gas refrigerant flowing out of the evaporator; and

a tapping temperature sensor configured to sense a tapping temperature of the supply water flowing out of the condenser,

wherein the control section obtains an evaporation temperature of the liquid refrigerant from the pressure sensed by the steam pressure sensor, calculates the superheat degree of the gas refrigerant by subtracting the evaporation temperature from the temperature sensed by the suction temperature sensor, and controls the refrigerant flow rate adjustment section such that the calculated superheat degree reaches a target superheat degree, and controls the supply water flow rate adjustment section such that the temperature sensed by the tapping temperature sensor reaches a target tapping temperature.

4. The supply-water warming system according to claim 3, further comprising:

a heat source temperature sensor configured to sense a temperature of the heat source fluid before the heat source fluid flows into the evaporator,

wherein the control section sets the target superheat degree according to the temperature sensed by the heat source temperature sensor.

5. The supply-water warming system according to claim 4, wherein

the control section increases the target superheat degree in a case where it is determined that fluctuation in the temperature sensed by the heat source temperature sensor is great.

6. The supply-water warming system according to claim 4, wherein

the control section decreases the target superheat degree in a case where it is determined that the temperature sensed by the heat source temperature sensor is stable.

7. The supply-water warming system according to claim 3, further comprising:

a supply water temperature sensor configured to sense a temperature of the supply water before the supply water flows into the condenser,

wherein the control section sets the target tapping temperature according to the temperature sensed by the supply water temperature sensor.

8. The supply-water warming system according to claim 3, further comprising:

a supply water temperature sensor configured to sense a temperature of the supply water before the supply water flows into the condenser,

wherein the target tapping temperature is settable to a value between an upper limit and a lower limit, and the lower limit is a value obtained by addition of a predetermined value to the temperature sensed by the supply water temperature sensor and increasing as the temperature sensed by the supply water temperature sensor increases.

9. The supply-water warming system according to claim 1, further comprising:

one or two bypass lines configured to cause the supply water to bypass the heat recovery heat exchanger and/or cause the heat source fluid to bypass the heat recovery heat exchanger; and

a preheating mode switching section configured to switch a preheating mode between a supply water preheating mode in which the supply water and the heat source fluid simultaneously flow in the heat recovery heat exchanger and a preheating stop mode in which at least one of the supply water or the heat source fluid flows in the one or two bypass lines.

10. The supply-water warming system according to claim 9, further comprising:

a pre-heat-exchanger-inflow supply water temperature sensor configured to sense a temperature of the supply water before the supply water flows into the heat recovery heat exchanger; and

a pre-heat-exchanger-inflow heat source temperature sensor configured to sense a temperature of the heat source fluid before the heat source fluid flows into the heat recovery heat exchanger,

wherein the control section compares a first sensed temperature obtained by the pre-heat-exchanger-inflow supply water temperature sensor and a second sensed temperature obtained by the pre-heat-exchanger-inflow heat source temperature sensor, controls the preheating mode switching section to execute the supply water preheating mode in a case where the first sensed temperature falls below the second sensed temperature, and controls the preheating mode switching section to execute the preheating stop mode in a case where the first sensed temperature exceeds the second sensed temperature.

11. The supply-water warming system according to claim 9, wherein

the control section includes a signal input unit configured to receive a preheating mode specifying signal for specifying a type which is the supply water preheating mode or the preheating stop mode, and a preheating mode switching control unit configured to control, according to the preheating mode specifying signal input to the signal input unit, the preheating mode switching section to execute the supply water preheating mode or the preheating stop mode.