METHOD FOR CONTROLLING NUMBER OF PUMPS, DEVICE FOR CONTROLLING NUMBER OF PUMPS, PUMP SYSTEM, HEAT SOURCE SYSTEM, AND PROGRAM

Abstract

A method for controlling number of pumps includes a process of increasing or decreasing the number of operating pumps based on a flow rate of a heat medium that is forcibly fed to a load (40) by a plurality of pumps connected in parallel or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps.

Description

TECHNICAL FIELD

The present invention relates to a method for controlling number of pumps, a device for controlling number of pumps, a pump system, a heat source system, and a program.

Priority is claimed on Japanese Patent Application No. 2014-017187, filed on Jan. 31, 2014, the content of which is incorporated herein by reference.

BACKGROUND ART

In a heat source system that supplies a heat medium such as cold water or hot water (hereinafter, “cold/hot water”) from a heat source machine to a load device such as an air conditioner, a plurality of secondary pumps that are connected in parallel between the heat source machine and the air conditioner are often installed to forcibly feed the heat medium to the air conditioner apart from the heat source machine again in addition to a primary pump that forcibly feeds the cold/hot water to the heat source machine. In the heat source system including the secondary pumps, a technique of deciding the number of secondary pumps that are operated so that a discharge flow rate to the load device is satisfied is used. Generally, in this technique, a threshold value serving as a reference for increasing or decreasing the number of pumps is set, and control is often performed such that an additional pump is started when the flow rate of the heat medium measured by measuring equipment installed in the middle of a supply path exceeds the threshold value thereof, whereas when the measured flow rate of the heat medium is the threshold value or less, a pump is stopped. However, if it is determined whether or not the number of operating pumps is increased or decreased based on only the measured flow rate, it is likely for an additional pump to be started even when there is still room in the capability of the pumps, that is, the frequency of the pumps is enough compared to the rated frequency.

For example, in a technique disclosed in Patent Literature 1, by changing the number of operating pumps using a flow rate as a threshold value which is decided at a crossing point between a curved line indicating a relation of a pump discharge pressure and a pump discharge flow rate which are decided for each of the number of operating secondary pumps and a control line indicating a correlation of a flow rate of a heat medium to be supplied to a load device and a pump discharge pressure necessary for it, the threshold value of the flow rate at which discharge pressure can be maintained even after the number of pumps is changed is set.

CITATION LIST

[Patent Literature]

[Patent Literature 1]

Japanese Patent No. 5261153

SUMMARY OF INVENTION

[Technical Problem]

In the case of the technique disclosed in Patent Literature 1, it is difficult to obtain a significant threshold value unless a pressure drop characteristic of a pipe is accurately detected, and a control line in which the pressure drop characteristic is reflected is obtained. The pressure drop of the pipe refers to loss of pump discharge pressure caused by friction occurring when a heat medium flows in a pipe, a curved pipe, resistance by a valve, or the like, and the pressure drop characteristic is a change characteristic of the pressure drop to the flow rate of the heat medium. Particularly, when the load device is an air conditioner, a pressure drop of a system is changed by a control valve with which the air conditioner is equipped, and thus a threshold value used for control of the number of operating pumps undergoes deviation unless a change in the control line is additionally considered. If the number of operating pumps is not changed at an appropriate timing, for example, the flow rate or the pressure of the heat medium changes due to the unnecessary change in the number of pumps, and it is hard to operate the heat source system stably.

The present invention provides a method for controlling number of pumps, a device for controlling number of pumps, a pump system, a heat source system, and a program.

[Solution to Problem]

According to a first aspect of the present invention, a method for controlling number of pumps includes a process of increasing or decreasing a number of operating pumps based on a flow rate of a heat medium that is forcibly fed to a load by a plurality of pumps connected in parallel or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps.

According to a second aspect of the present invention, the method for controlling number of pumps according to the first aspect further includes a process of acquiring a number-of-pumps determination flow rate value indicating the flow rate of the heat medium forcibly fed to the load from a measurement value of a discharge flow rate by the pumps in operation among the plurality of pumps, wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is increased when the number-of-pumps determination flow rate value is equal to or larger than a predetermined threshold value Gα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the number-of-pumps determination flow rate value is equal to or smaller than a predetermined threshold value Gβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

According to a third aspect of the present invention, the method for controlling number of pumps according to the first aspect further includes a process of calculating the heat load required by the load, wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is increased when the heat load is equal to or larger than a predetermined threshold value Lα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the heat load is equal to or smaller than a predetermined threshold value Lβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

According to a fourth aspect of the present invention, in the method for controlling number of pumps according to the second or third aspect, in the process of increasing or decreasing the number of operating pumps, a pump head of the pump is further compared with an increase permission pump head serving as a threshold value for increasing the number of pumps or a decrease permission pump head serving as a threshold value for decreasing the number of pumps, the number of operating pumps is increased only when the increase permission pump head is smaller than the pump head, and the number of operating pumps is decreased only when the decrease permission pump head is larger than the pump head.

According to a fifth aspect of the present invention, the method for controlling number of pumps according to the fourth aspect further includes a process of obtaining the increase permission pump head by calculating the pump head when a frequency of the pump is operated at the predetermined threshold value Fβ from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is increased and a predetermined correlation of the pump head for the discharge flow rate of the pump and obtaining the decrease permission pump head by calculating the pump head when the frequency of the pump is operated at the predetermined threshold value Fα from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is decreased and the predetermined correlation.

According to a sixth aspect of the present invention, the method for controlling number of pumps according to the second or third aspect further includes a process of acquiring a frequency command value after the number of operating pumps is increased and a frequency command value after the number of operating pumps is decreased based on a predetermined correlation between the pump head and the discharge flow rate of the pump at a predetermined frequency of the pump in operation under a condition that the pump head after the number of operating pumps is increased or decreased to be equal to a current pump head, wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the frequency command value after the number of operating pumps is increased is larger than the threshold value Fβ, and the number of operating pumps is decreased only when the frequency command value after the number of operating pumps is decreased is smaller than the threshold value Fα.

According to a seventh aspect of the present invention, the method for controlling number of pumps according to any one of the second to sixth aspect further includes a process of acquiring a pump efficiency after the number of operating pumps is increased, a pump efficiency after the number of operating pumps is decreased, and a current pump efficiency based on a predetermined correlation between the discharge flow rate and the pump efficiency at the predetermined frequency of the pump in operation, wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the pump efficiency after the number of operating pumps is increased is equal to or larger than the current pump efficiency, and the number of operating pumps is decreased only when the pump efficiency after the number of operating pumps is decreased is equal to or larger than the current pump efficiency.

According to an eighth aspect of the present invention, a device for controlling number of pumps includes a number-of-pumps control unit configured to increase or decrease the number of operating pumps that are connected in parallel to forcibly feed a heat medium to a load based on a flow rate of the heat medium forcibly fed to the load or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps.

According to a ninth aspect of the present invention, a pump system includes a plurality of pumps connected in parallel and the device for controlling number of pumps according to the eighth aspect, wherein the number of operating pumps is changed so that the pump head per pump and the flow rate measurement value are not changed.

According to a tenth aspect of the present invention, a heat source system includes a load, a plurality of heat source machines configured to forcibly feed a heat medium and connected in parallel, a secondary pump configured to further forcibly feed the heat medium forcibly fed from the plurality of heat source machines connected in parallel to the load, and the device for controlling number of pumps according to the eighth aspect.

According to an eleventh aspect of the present invention, a program causes a computer of a device for controlling number of pumps to function as a unit configured to increase or decrease the number of operating pumps based on a flow rate of a heat medium that is forcibly fed to a load by a plurality of pumps connected in parallel or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps.

[Advantageous Effects of Invention]

According to the method for controlling number of pumps, the device for controlling number of pumps, the pump system, the heat source system, and the program described above, it is possible to appropriately control the number of operating pumps at an appropriate timing without knowing characteristics of facilities such as the pressure drop characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a heat source system according to a first embodiment of the present invention.

FIG. 2 is a functional block diagram showing a device for controlling number of pumps according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a process flow of the device for controlling number of pumps according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing a heat source system according to a modified example of the first embodiment of the present invention.

FIG. 5 is a functional block diagram showing a device for controlling number of pumps according to the modified example of the first embodiment of the present invention.

FIG. 6 is a functional block diagram showing a device for controlling number of pumps according to a second embodiment of the present invention.

FIG. 7 is a diagram showing an example of Q-H characteristics indicating characteristics of a pump.

FIG. 8A is a diagram showing a change when the number of operating secondary pumps is increased from 1 to 2.

FIG. 8B is a diagram showing a change when the number of operating secondary pumps is increased from 1 to 2.

FIG. 9 is a diagram showing a process flow of the device for controlling number of pumps according to the second embodiment of the present invention.

FIG. 10 is a functional block diagram showing a device for controlling number of pumps according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a process flow of the device for controlling number of pumps according to the third embodiment of the present invention.

FIG. 12 is a functional block diagram showing a device for controlling number of pumps according to the fourth embodiment of the present invention.

FIG. 13 is a diagram showing an example of a correlation between a pump discharge flow rate and pump efficiency.

FIG. 14 is a diagram showing a process flow of the device for controlling number of pumps according to the fourth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a heat source system according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 is a schematic diagram showing the heat source system according to the first embodiment of the present invention.

As shown in FIG. 1, the heat source system of the present embodiment includes heat source machines 30, primary pumps 10, secondary pumps 20, a load 40, a flowmeter 21, and a device for controlling number of pumps 50.

The heat source machines 30 are devices that supply a heat medium for cooling or heating such as water to the load. The primary pumps 10 forcibly feed the heat medium to the heat source machines 30. The heat source machines 30 are devices that supply a heat medium for cooling or heating such as water to a load. In the heat source system according to the present embodiment, a plurality of combinations of the heat source machines 30 and the primary pumps 10 may be installed in parallel. FIG. 1 shows a state in which the plurality of primary pumps 10 are installed in parallel.

The secondary pumps 20 forcibly feed the heat medium fed from the heat source machines 30 to the load 40. The secondary pumps 20 are installed to be connected to each other in parallel, and control the flow rate of the heat medium to be supplied to the load 40 according to a request from the load 40.

The flowmeter 21 is a flowmeter that measures a flow rate per unit time of the heat medium forcibly fed from the pumps.

The load 40 is, for example, an air conditioner. The load 40 performs heat dissipation or heat absorption on the heat medium, and causes the resulting heat medium to flow back to the heat source machine 30.

The device for controlling number of pumps 50 is a device having a function of increasing or decreasing the number of operating secondary pumps 20 according to a requested load required by the load 40.

In FIG. 1, the two heat source machines 30, the two primary pumps 10, and the two secondary pumps 20 are installed, but the number of heat source machines 30, the number of primary pumps 10, and the number of secondary pumps 20 are not limited thereto. For example, six heat source machines 30, six primary pumps 10, and nine secondary pumps 20 may be installed.

In the heat source system, a device (not shown) that controls the number of operating heat source machines 30 such that a supply amount of the heat medium is adjusted according to the requested load of the load 40 may be installed.

FIG. 2 is a functional block diagram showing the device for controlling number of pumps according to the first embodiment of the present invention. The device for controlling number of pumps 50 according to the present embodiment will be described with reference to FIG. 2.

The device for controlling number of pumps 50 includes a number-of-pumps determination flow rate value acquiring unit 101, a number-of-pumps determination frequency value acquiring unit 102, a pump frequency setting unit 103, a flow rate acquiring unit 104, a number-of-pumps control unit 105, and a storage unit 200 as shown in FIG. 2.

The number-of-pumps determination flow rate value acquiring unit 101 reads and acquires a flow rate increase threshold value Gα or a flow rate decrease threshold value Gβ serving as a threshold value used when increasing or decreasing the number of operating secondary pumps 20 according to the flow rate from the storage unit 200. The number-of-pumps determination flow rate value acquiring unit 101 calculates the number-of-pumps determination flow rate value, for example, according to the following Formula (1).

$\begin{array}{cc}\left[\mathrm{Math}.1\right]& \\ \frac{G_{\mathrm{load}}}{\sum _i^nG_{0i}}& \left(1\right)\end{array}$

Here, Gload is a measurement value of the flow rate of the heat medium such as water forcibly fed from all the secondary pumps 20 which are in operation. G0i is a rated flow rate of the secondary pumps which are currently in operation. The number-of-pumps determination flow rate value is a ratio of the measurement values of the discharge flow rates by all the pumps in operation with respect to a sum of the rated flow rates of the secondary pumps in operation.

The number-of-pumps determination frequency value acquiring unit 102 reads and acquires a frequency increase threshold value Fα or a frequency decrease threshold value Fβ used when increasing or decreasing the number of operating secondary pumps 20 according to a frequency from the storage unit 200. The number-of-pumps determination frequency value acquiring unit 102 acquires a frequency command value that is output from the pump frequency setting unit 103 to the secondary pumps 20 from the pump frequency setting unit 103, and uses the acquired frequency command value as a number-of-pumps determination frequency value.

The pump frequency setting unit 103 gives a command indicating the frequency for operating the pumps to the secondary pump 20. The frequency is a frequency of electric power for rotating a motor for driving the secondary pump 20, and the pump frequency setting unit 103 controls an output of the pumps by designating the frequency and changing the number of revolutions of the pumps. The pump frequency setting unit 103 is assumed to output the same frequency command value to the plurality of secondary pumps 20 in the operation state.

The flow rate acquiring unit 104 acquires the flow rate of the heat medium measured by the flowmeter 21.

The number-of-pumps control unit 105 increases the number of operating pumps when the flow rate of the heat medium forcibly fed by the pump or the frequency of the pump satisfies a predetermined condition. In the present embodiment, the number of operating pumps is increased when the following two conditions are satisfied.

<Increase condition 1: determined based on flow rate>number-of-pumps determination flow rate value≧Gα  (2)

<Increase condition 2: determined based on frequency>number-of-pumps determination frequency value Fα  (3)

Here, the number-of-pumps determination frequency value is the same value as a frequency command value Fset that is output from the pump frequency setting unit 103 to the secondary pump 20. Fα is a threshold value acquired by the number-of-pumps determination frequency value acquiring unit 102.

In other words, when the ratio of the flow rates forcibly fed by all the secondary pumps 20 that are currently in operation with respect to the total sum of water feeding capabilities of the secondary pumps 20 in operation is equal to or larger than the threshold value Gα (Formula (2)), and the frequency command value output to each secondary pump 20 is equal to or larger than the threshold value Fα (Formula (3)), the number-of-pumps control unit 105 increases the number of operating secondary pumps 20.

Further, the number-of-pumps control unit 105 decreases the number of operating pumps when the flow rate of the heat medium forcibly fed by the pump or the frequency of the pump satisfies a predetermined condition. In the present embodiment, when the following two conditions are satisfied, the number of operating pumps is decreased.

<Decrease condition 1: determination based on flow rate>number-of-pumps determination flow rate value Gβ  (4)

Here, Gβ is a threshold value acquired by the number-of-pumps determination flow rate value acquiring unit 101.

<Decrease condition 2: determination based on frequency>number-of-pumps determination frequency value Fβ  (5)

Here, FP is a threshold value acquired by the number-of-pumps determination frequency value acquiring unit 102. The number-of-pumps determination frequency value is, for example, a frequency command value which is designated to the secondary pumps 20 by the pump frequency setting unit 103. In other words, when the ratio of the flow rates forcibly fed by all the secondary pumps 20 that are currently in operation with respect to the total sum of water feeding capabilities of the secondary pumps 20 that are currently in operation is equal to or smaller than the threshold value Gβ (Formula (4)), and the frequency command value output to each secondary pump 20 is equal to or smaller than the threshold value Fβ (Formula (5)), the number-of-pumps control unit 105 decreases the number of operating secondary pumps 20.

The storage unit 200 holds the threshold values Gα and Fα used for determining whether or not the number of pumps is increased or decreased, information indicating characteristics of the secondary pumps 20, or the like. The characteristic information is, for example, Q-H characteristics, a graph indicating a correlation between the discharge flow rate of the pumps and the pump efficiency, or the like.

FIG. 3 is a diagram showing a process flow of the device for controlling number of pumps according to the present embodiment.

A process of increasing or decreasing the number of operating secondary pumps 20 through the device for controlling number of pumps 50 will be described with reference to the process flow of FIG. 3.

It is assumed that the heat source system shown in FIG. 1 is operating, for example, the load 40 is the air conditioner, and when the user increases or decreases a temperature setting, the requested load is increased or decreased, and the device for controlling number of pumps 50 controls the number of operating secondary pumps 20 accordingly. Further, it is assumed that the sum of the flow rates of the secondary pumps 20 directly after the number of pumps is increased or decreased does not change from that before the number of pumps is increased or decreased, and the pump head (head of the pumps) per secondary pump 20 does not change.

First, the flow rate acquiring unit 104 acquires a flow rate per unit time measured by the flowmeter 21 (step S1). The flow rate measured by the flowmeter 21 is a total flow rate of the heat medium forcibly fed by the one or more secondary pumps 20. The measurement value is a value obtained by actually measuring the flow rate flowing through the pipe and thus can be considered to be a value in which the pressure drop characteristics of the pipe are reflected.

Then, the number-of-pumps determination flow rate value acquiring unit 101 reads and acquires the threshold values Gα and Gβ stored in the storage unit 200. The number-of-pumps determination flow rate value acquiring unit 101 calculates the number-of-pumps determination flow rate value using Formula (1) (step S2). The number-of-pumps determination flow rate value acquiring unit 101 outputs the values to the number-of-pumps control unit 105.

Then, the number-of-pumps determination frequency value acquiring unit 102 reads and acquires the threshold values Fα and Fβ stored in the storage unit 200. The number-of-pumps determination frequency value acquiring unit 102 acquires the pump frequency command value that is commanded from the pump frequency setting unit 103 to the secondary pump 20 as the number-of-pumps determination frequency value (step S3). The number-of-pumps determination frequency value acquiring unit 102 outputs the values to the number-of-pumps control unit 105.

Then, the number-of-pumps control unit 105 evaluates Formula (2) and Formula (3), and performs determination of the “increase condition 1” and the “increase condition 2” (step S4). Then, when both of the conditions are satisfied (Yes in step S4), the number-of-pumps control unit 105 increases the number of secondary pumps 20 by starting up one of the secondary pumps 20 that are currently in the stop state (step S5).

When it is determined through comparison that none of the “increase condition 1” and the “increase condition 2” is satisfied (No in step S4), the process proceeds to step S6.

Then, the number-of-pumps control unit 105 evaluates Formula (4) and Formula (5), and performs determination of the “decrease condition 1” and the “decrease condition 2” (step S6). Then, when both of the conditions are satisfied (Yes in step S6), the number-of-pumps control unit 105 decreases the number of secondary pumps 20 by stopping one of the secondary pumps 20 which are currently in operation (step S7).

When it is determined through comparison that none of the “decrease condition 1” and the “decrease condition 2” is satisfied (No in step S6), the process proceeds to step S8.

Finally, the device for controlling number of pumps 50 determines whether or not the heat source system has been stopped, for example, by an operation of the user according to a predetermined method. When the operation of the heat source system has been stopped (Yes in step S8), the present process flow ends. When the operation is continued (No in step S8), the process starting from step S1 is repeated.

Effects of the present embodiment will be described. For example, in a “first heat source system state” in which a value of the air conditioner is narrowed by a decrease in a load, and the pressure drop of the system is large, one secondary pump 20 is in operation, and the measurement value of the discharge flow rate at that time is 100 m³/h. On the other hand, in a “second heat source system state” in which the pressure drop is decreased by an increase in a load, one secondary pump 20 is in operation, and the measurement value of the discharge flow rate is 100 m³/h as well. Then, a threshold value for increasing the number of operating secondary pumps 20 from 1 to 2 is 100 m³/h.

At this time, in the “first heat source system state,” the pressure drop is large, and thus if the measurement value of the discharge flow rate is 100 m³/h although the secondary pump 20 is operating at a frequency of a value close to a maximum, control of increasing the number of operating secondary pumps 20 to 2 according to the threshold value that is set in advance is considered to be appropriate. On the other hand, in the “second heat source system state,” the pressure drop is small, and thus, for example, the secondary pump 20 is operated at a frequency that is about half a maximum frequency, and the flow rate of 100 m³/h is obtained. In this case, it is not necessarily appropriate to increase the number of operating secondary pumps 20, and there is also a possibility that the flow rate required by the load device can be supplied by increasing the frequency of the secondary pump 20 that is currently in operation. In this case, in the technique of the related art in which only the flow rate is used for determination as to whether or not the number of pumps is increased or decreased, the number of secondary pumps is increased. The increase in the number of pumps significantly changes the pressure and the flow rate of the heat medium flowing in the system.

According to the present embodiment, the determination is performed based on the frequency command value in addition to the actual measurement value of the flow rate including the pressure drop information of the system, and thus it is possible to increase or decrease the number of secondary pumps 20 without knowing the details of facilities such as the pressure drop. Further, it is determined whether or not the number of pumps is increased or decreased using the pump frequency command value, and thus it is possible to increase or decrease the number of secondary pumps 20 in view of an available capacity of the pump, and, for example, control of increasing the number of pumps although there is a room in capability of the pump can be prevented. Thus, an increase or decrease in the number of pumps does not occur often, and the heat source system can be operated more stably than in the technique of the related art. Similarly, even when the number of pumps is decreased, the number of pumps can be prevented from being decreased although the capability of the pump can be decreased by decreasing the frequency.

Modified Example

In a modified example of the present embodiment, a heat load required by the load 40 can be used instead of the flow rate of the heat medium. The modified example will be described below with reference to FIGS. 4 and 5.

FIG. 4 is a schematic diagram showing a heat source system according to the modified example of the present embodiment.

The heat source system of the modified example includes a thermometer 22 and a thermometer 23. The remaining configuration is the same as in the first embodiment.

The thermometer 22 is installed nearby an inlet of the load 40. The thermometer 22 measures the temperature of the heat medium to be supplied to the load 40.

The thermometer 23 is installed nearby an outlet of the load 40. The thermometer 23 measures the temperature of the heat medium to flow from the load 40 back to the heat source machine 30.

FIG. 5 is a functional block diagram showing the device for controlling number of pumps according to the modified example of the present embodiment.

The device for controlling number of pumps 50 of the modified example differs from that of the first embodiment in that the device for controlling number of pumps includes a temperature acquiring unit 110, and includes a number-of-pumps determination heat load acquiring unit 111 instead of the number-of-pumps determination flow rate value acquiring unit 101. The remaining configuration of the present embodiment is the same as in the first embodiment.

The temperature acquiring unit 110 acquires the temperatures of the heat medium measured by the thermometer 22 and the thermometer 23.

The number-of-pumps determination heat load acquiring unit 111 reads a heat load increase threshold value La and a heat load decrease threshold value Lβ serving as a predetermined threshold value from the storage unit 200. The number-of-pumps determination heat load acquiring unit 111 acquires the flow rate of the heat medium from the flow rate acquiring unit 104, acquires the temperatures of the heat medium measured by the thermometer 22 and the thermometer 23 from the temperature acquiring unit 110, and calculates a load (a heat load) required by the load 40. The heat load may be calculated using, for example, the following formula:

heat load=flow rate of heat medium×(|temperature of heat medium to flow back−temperature of the heat medium to be supplied|)×specific heat of heat medium×specific gravity of heat medium   (6)

Here, the “flow rate of the heat medium” is a value that is measured by the flowmeter 21 and acquired from the flow rate acquiring unit 104 by the number-of-pumps determination heat load acquiring unit 111. The “temperature of the heat medium to flow back” is a temperature measured by the thermometer 23 and a value acquired from the temperature acquiring unit 110 by the number-of-pumps determination heat load acquiring unit 111. The “temperature of the heat medium to be supplied” is a temperature measured by the thermometer 22 and a value acquired from the temperature acquiring unit 110 by the number-of-pumps determination heat load acquiring unit 111. The specific heat of the heat medium and the specific gravity of the heat medium are recorded in the storage unit 200 in advance, and the number-of-pumps determination heat load acquiring unit 111 reads the values from the storage unit 200.

In the present embodiment, the number-of-pumps control unit 105 increases the number of operating pumps when the heat load calculated by the number-of-pumps determination heat load acquiring unit 111 or the frequency of the pump acquired by the number-of-pumps determination frequency value acquiring unit 102 satisfies a predetermined condition. Specifically, the number of operating pumps is increased when the following two conditions are satisfied.

<Increase condition 1-1: determination based on heat load>heat load≧Lα  (7)

<Increase condition 2: determination based on frequency>number-of-pumps determination frequency value≧Fα  (8)

The number-of-pumps control unit 105 decreases the number of operating pumps when the heat load or the frequency of the pump satisfies a predetermined condition. Specifically, the number of operating pumps is decreased when the following two conditions are satisfied.

<Decrease condition 1-1: determination based on heat load>heat load≦Lβ   (9)

<Decrease condition 2: determination based on frequency>number-of-pumps determination frequency value≦Fβ   (10)

In the modified example, the increase condition 1-1 and the decrease condition 1-1 differ from those in the first embodiment. The increase condition 2 and the decrease condition 2 are the same as those in the first embodiment.

A process flow will be described. In the modified example, in step S1 of FIG. 3, the flow rate acquiring unit 104 acquires the flow rate measured by the flowmeter 21, and the temperature acquiring unit 110 further acquires the temperatures of the heat medium measured by the thermometer 22 and the thermometer 23. In step S2, the number-of-pumps determination heat load acquiring unit 111 reads the threshold values

Lα and Lβ stored in the storage unit 200. The number-of-pumps determination heat load acquiring unit 111 acquires the flow rate of the heat medium from the flow rate acquiring unit 104, and acquires the temperature of the heat medium to be supplied from the temperature acquiring unit 110 to the load 40 and the temperature of the heat medium to flow from the load 40 back to the heat source machine 30. Then, the number-of-pumps determination heat load acquiring unit 111 calculates the heat load using Formula (6). In step S4, the number-of-pumps control unit 105 performs determination of the “increase condition 1-1” and the “increase condition 2.” In step S6, the number-of-pumps control unit 105 performs determination of the “decrease condition 1-1” and the “decrease condition 2.” The remaining process steps in the present modified example are the same as those in the first embodiment.

The threshold values Gα, Gβ, Fα, Fβ, Lα, and Lβ used in the present embodiment and the modified example are values that are decided in advance through experimentation, simulation, or the like.

Second Embodiment

A heat source system according to a second embodiment of the present invention will be described below with reference to FIGS. 6 to 9.

The second embodiment relates to an example in which repetition of an increase or a decrease in the number of pumps is prevented so that the operation of the pumps is more stably performed in addition to the first embodiment.

FIG. 6 is a functional block diagram showing the device for controlling number of pumps according to the present embodiment.

The device for controlling number of pumps 50 of the present embodiment differs from that of the first embodiment in that the device for controlling number of pumps includes a pump head acquiring unit 107. The remaining configuration of the present embodiment is the same as in the first embodiment.

The pump head acquiring unit 107 acquires the pump head of the secondary pumps 20 that are currently in operation among the secondary pumps 20 or the pump head after the number of secondary pumps is increased or decreased based on the Q-H characteristics stored in the storage unit 200. Here, the pump head refers to a head of the pumps. The Q-H characteristics refer to a performance curve of the pumps indicating a relation between the discharge flow rate and the pump head when the pumps are operated at a maximum frequency. FIG. 7 shows an example of the Q-H characteristics. Generally, the discharge flow rate (Q) and the pump head (H) of the pumps have a relation in which the pump head decreases as the discharge flow rate increases, and the Q-H characteristics draw a different trajectory according to a type of pump. The Q-H characteristics indicating the Q-H correlation of the secondary pumps 20 used in the heat source system are stored in the storage unit 200, and the pump head acquiring unit 107 acquires the pump head corresponding to the discharge flow rate of secondary pumps per secondary pump 20 before and after the number of pumps is increased or decreased using the Q-H characteristics.

Next, a method of obtaining the pump head will be described more specifically. First, for example, symbols used for obtaining the pump head will be described in connection with an example in which the number of pumps is increased.

FIGS. 8A and 8B are diagrams showing a change when the number of operating secondary pumps 20 is increased from 1 to 2. Hereinafter, a secondary pump 20 in the operation state from the beginning is referred to as a “pump 20-1,” and a second secondary pump 20 to be added is referred to as a “pump 20-2.”

FIG. 8A is a diagram showing that one pump is in the operation state. The flow rate per unit time which is forcibly fed by one pump 20-1 is indicated by GA, and the total flow rate per unit time which is forcibly fed by all pumps 20-1 is indicated by GinA. In FIG. 8A, since the number of operating pumps is 1, GinA=GA. The frequency of the pump 20-1 is indicated by fA, and a head of the pump 20-1 is indicated by HA.

FIG. 8B is a diagram showing that two pumps are in the operation state. A flow rate per unit time which is forcibly fed by each of the pump 20-1 and the pump 20-2 is indicated by GB, and a total flow rate per unit time which is forcibly fed by the two pumps, that is, the pump 20-1 and the pump 20-2, is indicated by GinB. In FIG. 8B, since the number of operating pumps is 2, GinB=GB×2. A frequency of the pump 20-1 and the pump 20-2 is indicated by fB, and a head of the pump 20-1 and the pump 20-2 is indicated by HB. In other words, in FIG. 8B, the device for controlling number of pumps 50 performs control such that each of the secondary pumps 20 in the operation state has the same frequency regardless of the number of operating pumps. Further, the device for controlling number of pumps 50 performs control such that the total flow rate (GinA) and the pump head (HA) do not change before and after the number of secondary pumps 20 is increased or decreased when the number of secondary pumps 20 is increased or decreased. These conditions are prerequisites common to the first to fourth embodiments.

In summary, after the number of pumps is increased from n to n+m, respective values can be indicated as follows:

• • total flow rate: GinB=GinA;
  • discharge flow rate per pump: GB=(n/(n+m))GA;
  • pump head per pump: HB=HA; and
  • pump frequency: fB (the same in all pumps in operation).

Next, a method of obtaining the pump head will be described. The secondary pumps 20 are assumed to operate at a frequency 1, and a discharge flow rate 1 is assumed to be obtained. First, the discharge flow rate when the pumps operate at the maximum frequency can be obtained by multiplying the discharge flow rate 1 by a value obtained by dividing the maximum frequency by the frequency 1. Then, the Q-H characteristics are read using the obtained discharge flow rate of the maximum frequency, and the pump head corresponding to the discharge flow rate when the pumps operate at the maximum frequency is obtained. Then, the obtained pump head is multiplied by the square of the ratio of the current frequency 1 to the pump maximum frequency. A value obtained as a result is the pump head.

First, an increase permission pump head (HB′) is obtained using the following Formula (11).

$\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ H_B^{\prime }=F_{\left(\frac{n}{n+m}G_A\frac{f_{\max }}{F_{\beta }}\right)}\times {\left(\frac{F_{\beta }}{f_{\max }}\right)}^2& \left(11\right)\end{array}$

Here, the first term F(x) on the right side indicates a function for obtaining the pump head based on the discharge flow rate indicated by the Q-H characteristics. Fβ is the frequency decrease threshold value described in the first embodiment. Further, fmax is the maximum frequency (the pump maximum frequency) of each secondary pump 20. The pump head obtained using the frequency decrease threshold value Fβ indicates the pump head (the increase permission pump head) when the number of secondary pumps 20 is decreased by 1 from a state in which the number of secondary pumps 20 is increased by 1.

The pump head acquiring unit 107 similarly obtains the pump head (HB) in the state after the number of pumps is increased using the following Formula (12). Here, the frequency or the flow rate before the increase is used because the number of secondary pumps 20 is increased so that the pump head does not change, and thus the pump head after the increase is equal to the current pump head (before the increase).

$\begin{array}{cc}\left[\mathrm{Math}.3\right]& \\ H_B=F_{\left(G_A\frac{f_{\max }}{f_A}\right)}\times {\left(\frac{f_A}{f_{\max }}\right)}^2& \left(12\right)\end{array}$

Then, the number-of-pumps control unit 105 performs determination of the following condition using the values in addition to the two increase conditions in the first embodiment.

<Increase condition 3: determination based on pump head>increase permission pump head<pump head after increase   (13)

In other words, the number-of-pumps control unit 105 increases the number of operating secondary pumps 20 when it is equal to or larger than the increase permission pump head in addition to the “increase condition 1” and the “increase condition 2.” The increase permission pump head is a value that is obtained using the frequency decrease threshold value and used as a reference for decreasing the number of operating pumps after the number of operating pumps is increased. Since there is a possibility that the number of pumps will be decreased again if the pump head after the increase falls below the value even after the number of operating pumps is increased, the above condition is added in the present embodiment to eliminate such waste.

Next, a method of obtaining the decrease permission pump head through the pump head acquiring unit 107 will be described. The decrease permission pump head is a value used as a reference for increasing the pump after the number of operating pumps is decreased.

Similarly to the case of increase, respective values after the number of secondary pumps 20 is decreased from n to n−m can be indicated as follows.

• • water feeding flow rate: GinB=GinA
  • water feeding flow rate per pump: GB=(n/(n−m))GA
  • pump head per pump: HB=HA
  • pump frequency: fB (the same in all pumps in operation)

The decrease permission pump head may be obtained using the following Formula (14).

$\begin{array}{cc}\left[\mathrm{Math}.4\right]& \\ H_B^{\prime }=F_{\left(\frac{n}{n-m}G_A\frac{f_{\max }}{F_{\alpha }}\right)}\times {\left(\frac{F_{\alpha }}{f_{\max }}\right)}^2& \left(14\right)\end{array}$

Fα is the frequency increase threshold value described in the first embodiment. The pump head acquiring unit 107 obtains the pump head (HB) in the state after the number of pumps is decreased using the following Formula (12). The pump head after the decrease does not differ from the pump head before the number of pumps is decreased and thus can be obtained using Formula (12).

Then, the number-of-pumps control unit 105 performs determination of the following condition using the values in addition to the two decrease conditions in the first embodiment.

<Decrease condition 3: determination based on pump head>decrease permission pump head>pump head after decrease   (15)

In other words, the number-of-pumps control unit 105 decreases the number of operating secondary pumps 20 when it is equal to or less than the decrease permission pump head in addition to the “decrease condition 1” and the “decrease condition 2.” This condition is a condition in consideration of the fact that there is a possibility that the number of pumps will be increased again after the number of operating pumps is decreased, similarly to the case of the increase.

FIG. 9 is a diagram showing a process flow of the device for controlling number of pumps according to the present embodiment.

A process of increasing or decreasing the number of operating secondary pumps 20 through the device for controlling number of pumps 50 will be described with reference to a process flow of FIG. 9. The same processes as those in FIG. 3 are denoted by the same reference numerals.

First, steps S1 to S3 are the same as those in the first embodiment. In other words, the flow rate acquiring unit 104 acquires the flow rate measured by the flowmeter 21, the number-of-pumps determination flow rate value acquiring unit 101 acquires the threshold values Gα and Gβ and the number-of-pumps determination flow rate value, and the number-of-pumps determination frequency value acquiring unit 102 acquires the threshold values Fα and Fβ and the number-of-pumps determination frequency value.

Then, the pump head acquiring unit 107 obtains the pump head after the number of pumps is increased or decreased using Formula (12), obtains the increase permission pump head using Formula (11), and obtains the decrease permission pump head using Formula (14) (step S10).

Then, the number-of-pumps control unit 105 performs determination of the “increase condition 1,” the “increase condition 2,” and the “increase condition 3” (step S11). Then, when all the three conditions are satisfied (Yes in step S11), the number-of-pumps control unit 105 increases the number of operating secondary pumps 20 by 1 (step S5).

When it is determined through comparison that any of the “increase condition 1,” the “increase condition 2,” and the “increase condition 3” is not satisfied (No in step S11), the process proceeds to step S12.

Then, the number-of-pumps control unit 105 performs determination of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 3” (step S12). Then, when all the three conditions are satisfied (Yes in step S12), the number-of-pumps control unit 105 decreases the number of operating secondary pumps 20 by 1 (step S7).

When it is determined through comparison that any of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 3” is not satisfied (No in step S12), the process proceeds to step S8. The process of step S8 is the same as that in FIG. 3. In other words, the process starting from step S1 is repeated until the heat source system is stopped.

In the first embodiment, the determination criterion as to whether or not the number of secondary pumps 20 is increased or decreased using the measured flow rate and the pump frequency has been described. However, since the state after the number of pumps is increased or decreased is not considered in only the method of the first embodiment, the determination as to whether or not the number of pumps is increased or decreased is performed again, and there is a possibility that the increase and the decrease will be repeated.

According to the present embodiment, when the determination as to whether or not the number of pumps is increased or decreased is performed, the number of pumps is increased or decreased by performing a comparison of the pump operation state after the increase (decrease) with the pump head of the decrease (increase) threshold value estimated from the Q-H characteristics in addition to the flow rate measurement value and the pump frequency after the increase or the decrease, and thus the repetition of the increase and the decrease can be prevented.

The present embodiment may be combined with the modified example of the first embodiment.

Third Embodiment

Next, a heat source system according to a third embodiment of the present invention will be described with reference to FIGS. 10 and 11.

The third embodiment relates to an example in which repetition of an increase or a decrease in the number of pumps is prevented so that the operation of the pump is more stably performed in addition to the first embodiment, similarly to the second embodiment.

FIG. 10 is a functional block diagram showing a device for controlling number of pumps 50 according to the present embodiment.

The device for controlling number of pumps 50 of the present embodiment differs from that of the first embodiment in that the device for controlling number of pumps 50 includes a pump frequency estimation value acquiring unit 108. The remaining configuration of the present embodiment is the same as in the first embodiment.

The pump frequency estimation value acquiring unit 108 acquires a pump frequency estimation value after the increase and a pump frequency estimation value after the decrease serving as an estimation value of a frequency after the number of secondary pumps 20 is increased or decreased.

Specifically, the pump head after the increase may be obtained using Formula (16).

$\begin{array}{cc}\left[\mathrm{Math}.5\right]& \\ H_B=F_{\left(\frac{n}{n+m}G_A\frac{f_{\max }}{f_B}\right)}\times {\left(\frac{f_B}{f_{\max }}\right)}^2& \left(16\right)\end{array}$

In other words, the necessary discharge flow rate ((n/n+m)×GA) per pump after the increase at the pump frequency (fB) after the increase is obtained, and the pump head (HB) after the increase is obtained by multiplying the pump head acquired from the Q-H characteristics by the square of the ratio of the pump frequency (fB) after the increase to the pump maximum frequency (fmax) based on the discharge flow rate at the pump maximum frequency in this case.

Meanwhile, HB obtained using Formula (16) is the same as HA (the number of pumps is increased or decreased so that HB=HA), and HA may be calculated using the current pump frequency, the flow rate measurement value, and the Q-H characteristics (Formula (12)). The pump frequency estimation value acquiring unit 108 derives the frequency fB at which HB is HA using this relation from a map or an inverse function indicating a correlation between a frequency and a pump head which is prepared in advance, and uses fB as the pump frequency estimation value after the increase.

Then, the number-of-pumps control unit 105 performs increase permission determination (an “increase condition 4”) based on the frequency that prevents the decrease condition from being triggered again after the increase in addition to the “increase condition 1” and the “increase condition 2.”

<Increase condition 4: determination based on frequency>fB>Fβ  (17)

Here, fB is the pump frequency estimation value after the increase acquired by the pump frequency estimation value acquiring unit 108, and Fβ is the frequency decrease threshold value described in the first embodiment. In the present embodiment, since there is a possibility that the number of pumps will be decreased again unless the frequency after the increase exceeds the frequency decrease threshold value in addition to the “increase condition 1” and the “increase condition 2”, in order to prevent this, this condition is added for determination as to whether or not the number of pumps is increased.

The determination after the decrease is similarly performed. The pump frequency estimation value acquiring unit 108 substitutes the flow rate or the pump maximum frequency per pump after the decrease into Formula (18), and acquires the pump frequency estimation value fB after the decrease from a map or an inverse function using the fact that the value of Formula (18) is equal to HA.

$\begin{array}{cc}\left[\mathrm{Math}.6\right]& \\ H_B=F_{\left(\frac{n}{n-m}G_A\frac{f_{\max }}{f_B}\right)}\times {\left(\frac{f_B}{f_{\max }}\right)}^2& \left(18\right)\end{array}$

Then, the number-of-pumps control unit 105 performs decrease permission determination (the “decrease condition 4”) based on the frequency that prevents the increase condition from being triggered again after the decrease in addition to the “decrease condition 1” and the “decrease condition 2.”

<Decrease condition 4: determination based on frequency>fB<Fα  (19)

Here, fB is the pump frequency estimation value after the decrease acquired by the pump frequency estimation value acquiring unit 108, and Fα is the frequency increase threshold value described in the first embodiment. In other words, in the present embodiment, since there is a possibility that the number of pumps will be increased again unless the frequency after the decrease falls below the frequency increase threshold value in addition to the “decrease condition 1” and the “decrease condition 2” , in order to prevent this, this condition is added for determination as to whether or not the number of pumps is decreased.

FIG. 11 is a diagram showing a process flow of the device for controlling number of pumps according to the present embodiment.

A process of increasing or decreasing the number of operating secondary pumps 20 through the device for controlling number of pumps 50 will be described with reference to a process flow of FIG. 11. The same processes as those in FIG. 3 are denoted by the same reference numerals.

First, steps S1 to S3 are the same as those in the first embodiment. Then, the pump frequency estimation value acquiring unit 108 acquires an estimation value fB of the pump frequency after the number of pumps is increased or decreased according to the map or the inverse function (step S13).

Then, the number-of-pumps control unit 105 performs determination of the “increase condition 1,” the “increase condition 2,” and the “increase condition 4” (step S14). Then, when all the three conditions are satisfied (Yes in step S14), the number-of-pumps control unit 105 increases the number of operating secondary pumps 20 by 1 (step S5).

When it is determined through comparison that any of the “increase condition 1,” the “increase condition 2,” and the “increase condition 4” is not satisfied (No in step S14), the process proceeds to step S15.

Then, the number-of-pumps control unit 105 performs determination of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 4” (step S15). Then, when all the three conditions are satisfied (Yes in step S15), the number-of-pumps control unit 105 decreases the number of operating secondary pumps 20 by 1 (step S7).

When it is determined through comparison that any of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 3” is not satisfied (No in step S12), the process proceeds to step S8. The process of step S8 is the same as that in FIG. 3. In other words, the process starting from step S1 is repeated until the heat source system is stopped.

According to the present embodiment, the pump frequency after the increase (decrease) is estimated, and the value is compared with the frequency decrease (increase) threshold value. Then, in addition to the two conditions described in the first embodiment, when the pump frequency estimation value after the increase exceeds the frequency decrease threshold value, the number of secondary pumps 20 is increased. Similarly, in addition to the two conditions described in the first embodiment, when the pump frequency estimation value after the decrease falls below the frequency increase threshold value, the number of secondary pumps 20 is decreased. Since the frequency after the number of secondary pumps 20 is increased or decreased is considered, the repetition of the increase and the decrease can be prevented.

The present embodiment may be combined with the modified example of the first embodiment.

Fourth Embodiment

A heat source system according to a fourth embodiment of the present invention will be described below with reference to FIGS. 12 to 14.

The fourth embodiment relates to an example in which the number of operating pumps is changed in view of the pump efficiency in addition to the first to third embodiments.

FIG. 12 is a functional block diagram showing a device for controlling number of pumps according to the present embodiment.

The device for controlling number of pumps 50 of the present embodiment differs from that of the first embodiment in that the device for controlling number of pumps 50 includes a pump frequency estimation value acquiring unit 108 and a pump efficiency acquiring unit 109. The remaining configuration of the present embodiment is the same as in the first embodiment.

The pump frequency estimation value acquiring unit 108 acquires the pump frequency estimation value after the increase and the pump frequency estimation value after the decrease using the map or the inverse function as described above in the third embodiment.

The pump efficiency acquiring unit 109 acquires the estimation value of the pump efficiency after the number of secondary pumps 20 is increased or decreased, for example, using a graph indicating a correlation between the discharge flow rate and the pump efficiency of the pump stored in the storage unit 200. FIG. 13 shows an example of the correlation between the discharge flow rate and the pump efficiency when the pump is operated at the maximum frequency. FIG. 13 shows that the pump efficiency changes according to the discharge flow rate of the pump. When the number of operating secondary pumps 20 is increased or decreased, the discharge flow rate per pump changes, and thus the pump efficiency can be understood to change accordingly.

A current pump efficiency η_A per pump in the state before the increase is obtained using the following Formula (20).

$\begin{array}{cc}\left[\mathrm{Math}.7\right]& \\ {\eta }_A={\eta }_{\left(G_A\frac{f_{\max }}{f_A}\right)}& \left(20\right)\end{array}$

Here, η(x) is a function indicating a relation between the discharge flow rate and the pump efficiency of the pump.

Similarly, the pump efficiency η_B per pump after the increase is obtained using the following Formula (21).

$\begin{array}{cc}\left[\mathrm{Math}.8\right]& \\ {\eta }_B={\eta }_{\left(\frac{n}{n+m}G_A\frac{f_{\max }}{f_B}\right)}& \left(21\right)\end{array}$

Here, f_B is the pump frequency estimation value after the increase calculated by the pump frequency estimation value acquiring unit 108.

Then, the number-of-pumps control unit 105 performs increase permission determination (the “increase condition 5”) based on the pump efficiency in addition to the “increase condition 1” and the “increase condition 2.”

<Increase condition 5: determination based on pump efficiency>η_B≧η_A   (22)

In other words, the number-of-pumps control unit 105 does not increase the number of pumps unless the pump efficiency after the increase is equal to or larger than the pump efficiency before the increase in addition to the “increase condition 1” and the “increase condition 2.”

Similarly, the pump efficiency acquiring unit 109 obtains the pump efficiency per pump after the decrease using the following Formula (23).

$\begin{array}{cc}\left[\mathrm{Math}.9\right]& \\ {\eta }_B={\eta }_{\left(\frac{n}{n-m}G_A\frac{f_{\max }}{f_B}\right)}& \left(23\right)\end{array}$

Then, the number-of-pumps control unit 105 performs decrease permission determination (the “decrease condition 5”) based on the pump efficiency in addition to the “decrease condition 1” and the “decrease condition 2.”

<Decrease condition 5: determination based on pump efficiency>η_B≧η_A   (24)

In other words, the number-of-pumps control unit 105 does not decrease the number of pumps unless the pump efficiency after the decrease is equal to or larger than the pump efficiency before the decrease in addition to the “decrease condition 1” and the “decrease condition 2.”

In the first to third embodiments, since the pump efficiency is not considered, there is a possibility that an increase or decrease in the number of pumps will cause the pumps to be operated at an operation point at which the efficiency is bad.

According to the present embodiment, because the pump efficiency is considered, it is possible to increase or decrease the number of pumps while suppressing power consumption.

FIG. 14 is a diagram showing a process flow of the device for controlling number of pumps according to the present embodiment.

A process of increasing or decreasing the number of operating secondary pumps 20 through the device for controlling number of pumps 50 will be described with reference to a process flow of FIG. 14. The same processes as those in FIG. 11 are denoted by the same reference numerals.

Steps S1 to S3 are the same as those in the first to third embodiments. Step S13 is the same as in the third embodiment (FIG. 11).

Then, the pump efficiency acquiring unit 109 acquires the pump efficiencies before and after the number of pumps is increased or decreased (step S17).

Then, the number-of-pumps control unit 105 performs determination of the “increase condition 1,” the “increase condition 2,” and the “increase condition 5” (step S18). Then, when all the three conditions are satisfied (Yes in step S18), the number-of-pumps control unit 105 increases the number of operating secondary pumps 20 by 1 (step S5).

When it is determined through comparison that any of the “increase condition 1,” the “increase condition 2,” and the “increase condition 5” is not satisfied (No in step S18), the process proceeds to step S18.

Then, the number-of-pumps control unit 105 performs determination of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 5” (step S18). Then, when all the three conditions are satisfied (Yes in step S18), the number-of-pumps control unit 105 decreases the number of operating secondary pumps 20 by 1 (step S7).

When it is determined through comparison that any of the “decrease condition 1,” the “decrease condition 2,” and the “decrease condition 5” is not satisfied (No in step S18), the process proceeds to step S8. The process of step S8 is the same as in FIG. 3. In other words, the process starting from step S1 is repeated until the heat source system is stopped.

The present embodiment may be combined with the second or third embodiment as well as the first embodiment and the modified example of the first embodiment. When the present embodiment is combined with the second or third embodiment, it is possible to prevent the repetition of the increase and the decrease in the number of secondary pumps 20 and decide the number of operating pumps so that the flow rate measurement value to the load is satisfied while searching for a good operation point at which the pump efficiency is good, and thus an energy saving effect can be expected.

The device for controlling number of pumps includes an internal computer. The steps of each process of the device for controlling number of pumps is stored in a computer readable recording medium in the form of a program, and the above process is performed by reading the program through the computer. Here, the computer readable recording medium refers to a magnetic disk, a magneto-optical disc, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. The computer program may be delivered to the computer via a communication line, and the computer that has received the computer program may execute the program.

The program may be configured to implement some of the above-described functions.

Further, the program may be configured to implement the above-described functions in combination with a program previously recorded in a computer system, that is, may be a differential file (a differential program).

In addition, the components in the above embodiments can be appropriately replaced with known components within the scope not departing from the gist of the present invention. Further, claims of the invention are not limited to the above embodiments, and various changes can be made within the scope not departing from the gist of the present invention.

INDUSTRIAL APPLICABILITY

According to the method for controlling number of pumps, the device for controlling number of pumps, the pump system, the heat source system, and the program, it is possible to appropriately control the number of operating pumps at an appropriate timing without knowing characteristics of facilities such as the pressure drop characteristics.

REFERENCE SIGNS LIST

• 10 Primary pump
• 20 Secondary pump
• 21 Flowmeter
• 22 Thermometer
• 23 Thermometer
• 30 Heat source machine
• 40 Load
• 50 Device for controlling number of pumps
• 101 Number-of-pumps determination flow rate value acquiring unit
• 102 Number-of-pumps determination frequency value acquiring unit
• 103 Pump frequency setting unit
• 104 Flow rate acquiring unit
• 105 Number-of-pumps control unit
• 107 Pump head acquiring unit
• 108 Pump frequency estimation value acquiring unit
• 109 Pump efficiency acquiring unit
• 110 Temperature acquiring unit
• 111 Number-of-pumps determination heat load acquiring unit
• 200 Storage unit

Claims

1-11. (canceled)

12. A method for controlling number of pumps, comprising:

a process of acquiring a number-of-pumps determination flow rate value indicating a flow rate of a heat medium forcibly fed to a load from a measurement value of a discharge flow rate by the pumps in operation among a plurality of pumps, and

a process of increasing or decreasing a number of operating pumps based on the flow rate of the heat medium that is forcibly fed to the load by the plurality of pumps connected in parallel or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is increased when the number-of-pumps determination flow rate value is equal to or larger than a predetermined threshold value Gα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the number-of-pumps determination flow rate value is equal to or smaller than a predetermined threshold value Gβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

13. A method for controlling number of pumps, comprising:

a process of calculating a heat load required by a load, and

a process of increasing or decreasing a number of operating pumps based on a flow rate of a heat medium that is forcibly fed to the load by the plurality of pumps connected in parallel or the heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is increased when the heat load is equal to or larger than a predetermined threshold value Lα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the heat load is equal to or smaller than a predetermined threshold value Lβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

14. The method for controlling number of pumps according to claim 12,

wherein, in the process of increasing or decreasing the number of operating pumps, a pump head of the pump is further compared with an increase permission pump head serving as a threshold value for increasing the number of pumps or a decrease permission pump head serving as a threshold value for decreasing the number of pumps, the number of operating pumps is increased only when the increase permission pump head is smaller than the pump head, and the number of operating pumps is decreased only when the decrease permission pump head is larger than the pump head.

15. The method for controlling number of pumps according to claim 14, further comprising:

a process of obtaining the increase permission pump head by calculating the pump head when a frequency of the pump is operated at the predetermined threshold value Fβ from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is increased and a predetermined correlation of the pump head for the discharge flow rate of the pump and obtaining the decrease permission pump head by calculating the pump head when the frequency of the pump is operated at the predetermined threshold value Fα from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is decreased and the predetermined correlation.

16. The method for controlling number of pumps according to claim 12, further comprising:

a process of acquiring a frequency command value after the number of operating pumps is increased and a frequency command value after the number of operating pumps is decreased based on a predetermined correlation between the pump head and the discharge flow rate of the pump at a predetermined frequency of the pump in operation under a condition that the pump head after the number of operating pumps is increased or decreased to be equal to a current pump head,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the frequency command value after the number of operating pumps is increased is larger than the threshold value Fβ, and the number of operating pumps is decreased only when the frequency command value after the number of operating pumps is decreased is smaller than the threshold value Fα.

17. The method for controlling number of pumps according to claim 12, further comprising:

a process of acquiring a pump efficiency after the number of operating pumps is increased, a pump efficiency after the number of operating pumps is decreased, and a current pump efficiency based on a predetermined correlation between the discharge flow rate and the pump efficiency at the predetermined frequency of the pump in operation,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the pump efficiency after the number of operating pumps is increased is equal to or larger than the current pump efficiency, and the number of operating pumps is decreased only when the pump efficiency after the number of operating pumps is decreased is equal to or larger than the current pump efficiency.

18. A device for controlling number of pumps, comprising:

a number-of-pumps determination flow rate value acquiring unit configured to acquire a number-of-pumps determination flow rate value indicating a flow rate of a heat medium forcibly fed to a load from a measurement value of a discharge flow rate by the pumps in operation among a plurality of pumps, and

a number-of-pumps control unit configured to increase or decrease the number of operating pumps that are connected in parallel to forcibly feed the heat medium to the load based on the flow rate of the heat medium forcibly fed to the load or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps,

wherein, the number-of-pumps control unit is configured so that the number of operating pumps is increased when the number-of-pumps determination flow rate value is equal to or larger than a predetermined threshold value Gα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the number-of-pumps determination flow rate value is equal to or smaller than a predetermined threshold value Gβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

19. A pump system, comprising:

a plurality of pumps connected in parallel; and

the device for controlling number of pumps according to claim 18,

wherein the number of operating pumps is changed so that the pump head per pump and the flow rate measurement value are not changed.

20. A heat source system, comprising:

a load;

a plurality of heat source machines configured to forcibly feed a heat medium and connected in parallel;

a secondary pump configured to further forcibly feed the heat medium forcibly fed from the plurality of heat source machines connected in parallel to the load; and

the device for controlling number of pumps according to claim 18.

21. A non-transitory computer-readable storage medium storing a program causing a computer of a device for controlling number of pumps to function as:

a number-of-pumps determination flow rate value acquiring unit configured to acquire a number-of-pumps determination flow rate value indicating a flow rate of a heat medium forcibly fed to a load from a measurement value of a discharge flow rate by the pumps in operation among a plurality of pumps, and

a unit configured to increase or decrease the number of operating pumps based on the flow rate of the heat medium that is forcibly fed to the load by the plurality of pumps connected in parallel or a heat load required by the load and a frequency command value commanded to each pump in operation among the plurality of pumps

wherein, the unit configured to increase or decrease the number of operating pumps is configured so that the number of operating pumps is increased when the number-of-pumps determination flow rate value is equal to or larger than a predetermined threshold value Gα, and the frequency command value commanded to each pump is equal to or larger than a predetermined threshold value Fα, and the number of operating pumps is decreased when the number-of-pumps determination flow rate value is equal to or smaller than a predetermined threshold value Gβ, and the frequency command value commanded to each pump is equal to or smaller than a predetermined threshold value Fβ.

22. The method for controlling number of pumps according to claim 13,

wherein, in the process of increasing or decreasing the number of operating pumps, a pump head of the pump is further compared with an increase permission pump head serving as a threshold value for increasing the number of pumps or a decrease permission pump head serving as a threshold value for decreasing the number of pumps, the number of operating pumps is increased only when the increase permission pump head is smaller than the pump head, and the number of operating pumps is decreased only when the decrease permission pump head is larger than the pump head.

23. The method for controlling number of pumps according to claim 22, further comprising:

a process of obtaining the increase permission pump head by calculating the pump head when a frequency of the pump is operated at the predetermined threshold value Fβ from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is increased and a predetermined correlation of the pump head for the discharge flow rate of the pump and obtaining the decrease permission pump head by calculating the pump head when the frequency of the pump is operated at the predetermined threshold value Fα from the pump head calculated based on the discharge flow rate of the pump after the number of operating pumps is decreased and the predetermined correlation.

24. The method for controlling number of pumps according to claim 13, further comprising:

a process of acquiring a frequency command value after the number of operating pumps is increased and a frequency command value after the number of operating pumps is decreased based on a predetermined correlation between the pump head and the discharge flow rate of the pump at a predetermined frequency of the pump in operation under a condition that the pump head after the number of operating pumps is increased or decreased to be equal to a current pump head,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the frequency command value after the number of operating pumps is increased is larger than the threshold value Fβ, and the number of operating pumps is decreased only when the frequency command value after the number of operating pumps is decreased is smaller than the threshold value Fα.

25. The method for controlling number of pumps according to claim 13, further comprising:

a process of acquiring a pump efficiency after the number of operating pumps is increased, a pump efficiency after the number of operating pumps is decreased, and a current pump efficiency based on a predetermined correlation between the discharge flow rate and the pump efficiency at the predetermined frequency of the pump in operation,

wherein, in the process of increasing or decreasing the number of operating pumps, the number of operating pumps is further increased only when the pump efficiency after the number of operating pumps is increased is equal to or larger than the current pump efficiency, and the number of operating pumps is decreased only when the pump efficiency after the number of operating pumps is decreased is equal to or larger than the current pump efficiency.