Heat Pump for Heating Swimming Pool Water

Abstract

The invention relates to a heat pump. It relates to a heat pump which, in a primary circuit, comprises a compressor (10), a condenser (12) forming a heat exchanger between the refrigerating fluid and the swimming pool water, an expander (14) and an evaporator (16) forming a heat exchanger between the external surroundings and the refrigerating fluid. The condenser (12) comprises two heat exchange circuits and the heat pump comprises a pressure sensor (18), a member for switching the circulation of the refrigerating fluid between states in which it is circulated in just one or in at least two of the heat exchange circuits, and a member for controlling the switching member according to the value of the signal from the sensor (18). Application to the heating of swimming pool water.

Description

The present invention relates to a heat pump intended for heating swimming pool water, and a method for heating swimming pool water.

Heat pumps are thermodynamic systems which comprise a primary circuit of refrigerating fluid which comprises a compressor which feeds a condenser forming a heat exchanger between the refrigerating fluid and a heat source, an expander and an evaporator forming a heat exchanger. The heat exchangers exchange heat with a cold source and a hot source, one of which is an external medium, for example atmospheric air or a flow of water.

The document U.S. Pat. No. 5,272,885 describes a heat pump system used for the air conditioning of premises. It includes on the one hand an assembly forming a heat pump and on the other hand various user circuits. In this use, the external medium is constituted by a water supply unit. In the air heating mode, the apparatus of this document cools the water of the water supply unit, and in the air cooling mode, the apparatus draws heat from the air of internal air conditioning units and heats the water of the water supply unit.

The apparatus is very complicated, since it comprises a number of control systems: an internal controller with each conditioning unit, a distribution controller, and an external controller. All these controllers control all-or-nothing or gradual regulation (regulation of the opening of flow rate regulating valves, variable capacity compressor, gradual regulation of expander, control of complementary opening of flow rate regulating valve, etc.). A number of sensors are incorporated in the pump and in each conditioning unit. Two valves can switch complementary heat exchangers into the circuit.

This apparatus has been described because it shows that simple air conditioning of premises by the use of a heat pump may be very complicated, i.e. may require a number of devices having the functions of detection, regulation, control, etc. and which are subject to breakdowns, so that a specialist staff member is necessary for the setting up of such a heat pump. The system should be adapted to permit the heating of water instead of air conditioning.

The documents GB-2 015 139 and 406 137 describe the switching of heat exchange devices between states providing different heat exchange surfaces areas.

It is already known to use heat pumps for heating swimming pool water. The heat pumps comprise a primary refrigerating fluid circuit which comprises, as indicated in FIG. 1, a compressor 10 which feeds a condenser 12 (which forms a heat exchanger) between the refrigerating fluid and the swimming pool water to be heated, an expander 14 and an evaporator 16 (which forms a heat exchanger) between the external medium, for example the outside air, and the refrigerating fluid.

The characteristics of the exchangers, especially their dimensions, and the regulation of the expander and of the compressor, are optimised for a specific operating mode. In particular, the condenser is intended to permit the heat pump to provide its maximum power while maintaining an optimum operating mode from the point of view of the refrigerating circuit (pressure and temperature of the refrigerating fluid).

When such a heat pump is used for heating swimming pool water, certain operating parameters have specific values. Thus, even if the swimming pool water is very cold, scarcely above 0° C., the user hopes to obtain a temperature generally between 15 and 32° C. Moreover, the water circulation flow rate of the swimming pool is customarily of the order of 5 to 15 m³/hr.

It may be imagined therefore that when the thermal exchange is very great because the flow rate of water circulating in the condenser is very high and/or because the water temperature is very low, the refrigerating fluid is cooled to a very great degree, such that the pressure of the refrigerating fluid in the condenser is very low. The output of the heat pump, defined in general by its performance coefficient, is then reduced and it may even occur that the heat pump exhibits an operating fault and that it is even damaged.

On the other hand, if the thermal exchange in the condenser is reduced, because the water flow rate is low or because the temperature of the swimming pool water is high, the refrigerating fluid is heated to a significant degree and causes a pressure increase in the condenser.

The output of the heat pump is then also reduced, the correct operation may be disturbed, and the heat pump may even be damaged. In particular, beyond a certain pressure, the machine is stopped by a safety pressure sensitive switch.

In order to take this practical situation into account, swimming pool heat pumps generally include a hydraulic branch circuit located upstream of the heat pump and making it possible to regulate the water flow rate circulating in the secondary circuit of the condenser (exchanger) of the heat pump, so that the thermal exchange remains optimum and the operation of the heat pump is satisfactory. The installation should therefore include a regulating device intended to vary the water flow rate circulating in the condenser. Taking into account the water flow rates treated, such a regulating device is tricky to operate and is expensive. Very often it is simply replaced by a simple manual device which no longer provides any regulating function.

Thus, the known heat pumps present problems linked at least in part to the defects of complexity, cost and susceptibility to breakdowns indicated previously with reference to the document U.S. Pat. No. 5,272,885. These problems represent a serious nuisance in the case of swimming pools where the owners have no technical knowledge regarding the operation of heat pumps in general.

The aim of the invention is to solve the problems posed, or at least reduce their severity, by simplification of the heat pumps for heating swimming pool water which permits in particular a reduction in cost and susceptibility to breakdowns.

According to the invention, the problem posed is solved by varying the thermal exchange capacity of the refrigerating fluid heat exchange circuit of the condensers and not by varying the water flow rate which circulates in the condenser. The variation may be effected between only two values, with simple and robust means.

More precisely, according to the invention, when the water flow rate is high and the water temperature is low at the inlet of the secondary circuit of the condenser, i.e. when the secondary circuit of the condenser has a large capacity for absorbing calories, the heat exchange surface area of the primary circuit of the condenser is automatically reduced.

Conversely, when the water flow rate is reduced and the water is at a high temperature at the inlet of the condenser, and therefore has a low capacity for absorbing calories, the heat exchange surface area of the refrigerating fluid primary circuit of the condenser is automatically increased.

Thus, the same calorific power can substantially be transmitted to the secondary circuit of the condenser, and the primary circuit of the heat pump can operate in an optimum mode of pressure/temperature operation of the refrigerating fluid.

This result is obtained in practice by the use of a condenser in which the primary circuit comprises a plurality of heat exchange circuits, just one or more of which are switched into the circuit. In the condenser, the refrigerating fluid primary circuit always includes at least one heat exchange circuit, and at least one other heat exchange circuit can be switched into the circuit by means of at least one switching member, under the control of a control member which is connected to a sensor for detecting an operating parameter, such as the refrigerating fluid vapour pressure between the compressor and the expander.

Thus, when the measured pressure increases, the primary circuit of the expander is increased by switching additional heat exchange circuits into the circuit, and the operation is reversed when the measured pressure decreases.

More precisely, the invention relates to a heat pump intended for heating swimming pool water, of the type which comprises, in a primary circuit of refrigerating fluid, a compressor, a condenser forming a heat exchanger between the refrigerating fluid and the swimming pool water circulating in a secondary circuit, an expander, and an evaporator forming a heat exchanger between the external medium and the refrigerating fluid; according to the invention, the condenser comprises at least two heat exchange circuits, and the heat pump comprises a sensor for detecting a parameter of the operation of the heat pump, at least one member for switching the circulation of the refrigerating fluid between a state in which it is circulated in just one of the heat exchange circuits, and a state in which it is circulated in at least two of the heat exchange circuits, and a member for controlling the switching member at least according to the value of the signal from the sensor.

Preferably, at least one switching member comprises at least one solenoid valve.

Preferably, the sensor for detecting an operating parameter of the heat pump detects the pressure of the refrigerating fluid at the high pressure part of the refrigerating circuit, for example between the compressor and the condenser.

In one embodiment, the heat pump comprises at least two heat exchange circuits which are disposed in series in the condenser. It may then further comprise a branch circuit with respect to one of the heat exchange circuits.

In another embodiment, the heat pump comprises at least two heat exchange circuits disposed in parallel in the condenser.

The invention also relates to a method for heating swimming pool water by means of a heat pump according to the preceding paragraphs, which comprises the measurement of an operating parameter of the heat pump, the comparison of the measured value of the parameter with a threshold and, when the parameter exceeds a threshold, the control of the switching of the refrigerating fluid circulation in a heat exchange circuit.

Preferably, the comparison with a threshold comprises the use of two different thresholds, depending on whether the parameter increases or decreases, so that control is obtained with a hysteresis effect.

Other characteristics and advantages of the invention will become clearer from the following description of an exemplary embodiment, provided with reference to the appended drawings, in which:

FIG. 1, already described, shows a diagram of a heat pump used for heating swimming pool water;

FIGS. 2 and 3 show two examples of assembly of heat exchange circuits of the primary circuit of the condenser of the heat pump;

FIG. 4 is a diagram of a heat pump condenser according to the invention; and

FIG. 5 is a perspective view, with parts removed, of an example of the condenser shown diagrammatically in FIG. 4.

As FIG. 1 indicates, the compressor 10 brings the refrigerating liquid, in the vapour state, to a high pressure, the pressure being advantageously measured by a sensor 18. The refrigerating fluid in the vapour state passes into the condenser 12 and circulates in a primary circuit part 20.

The primary circuit part 20 of the condenser 12, according to the invention, may comprise at least two heat exchange circuits 22, arranged in series, and one of which may have a branch circuit 24 which is switched into the circuit or not by a solenoid valve 26. When the valve 26 is open, the refrigerating fluid circulates in series in the two heat exchange circuits 22, for example two coils, whereas, when the valve 26 feeds the branch circuit 24, only the second circuit 22 is fed.

FIG. 3 shows a variant in which heat exchange circuits 22 are arranged in parallel and each heat exchange circuit, other than the first, is switched into the circuit or not by the control of an associated solenoid valve 28.

The series circuit of FIG. 2, like the parallel circuit of FIG. 3, may of course comprise a greater number of heat exchange circuits, i.e. coils, as suggested by the interrupted lines.

In addition, it is possible to combine series and parallel devices such as are illustrated in FIGS. 2 and 3.

The important characteristic of the invention is that, by means of the solenoid valves 26, 28, the heat exchange capacity of the primary circuit 20 of the condenser 12 can be varied to a plurality of values so that the heat pump is always working under its optimum operating conditions.

FIG. 4 shows an example of a condenser 12 according to the invention. In this example, the water passes through an inlet 30 to the vicinity of the opposite end of the condenser 12 where it meets the bottom 31 of a deflector 32 which causes the water to return to the same side that it entered, before being deflected again by the end of the outer body 34 towards a water outlet 36.

When it circulates between the central pipe and the deflector 32, the water flows on the surface of a coil 38 forming a first heat exchange circuit 22. When it circulates between the deflector 32 and the outer wall of the body 34, the water flows on the surface of another coil 40 forming a second heat exchange circuit 22 of the primary circuit.

FIG. 4 does not show the connections of the pipes or the solenoid valve permitting the arrangement in series or in parallel of the two coils 38 and 40.

FIG. 5 shows a practical embodiment of the condenser shown in FIG. 4, with the same reference numbers as in the latter.

Although it has been indicated that the variation of the heat exchange surface area of the condenser was effected by measurement of the pressure at the outlet of the condenser, it is possible to measure other parameters. In fact, it is generally desirable to monitor on the one hand the pressure and on the other hand the temperature of the refrigerating fluid, at least at one location of the primary circuit. It is in fact these two parameters which are the most important for obtaining the best performance coefficient of the heat pump. The measured parameter may therefore be any combination of parameters commonly used for this purpose in heat pump technology.

Claims

1. Heat pump intended for heating swimming pool water, of the type which comprises, in a primary circuit of refrigerating fluid:

a compressor (10),

a condenser (12) forming a heat exchanger between the refrigerating fluid and the swimming pool water circulating in a secondary circuit,

an expander (14), and

an evaporator (16) forming a heat exchanger between the external medium and the refrigerating fluid, characterized in that

the condenser (12) comprises at least two heat exchange circuits (22), and

the heat pump comprises a sensor (18) for detecting an operating parameter of the heat pump, at least one member (26, 28) for switching the circulation of the refrigerating fluid between a state in which it is circulated in just one of the heat exchange circuits (22), and a state in which it is circulated in at least two of the heat exchange circuits (22), and a member for controlling the switching member at least according to the value of the signal from the sensor (18).

2. Heat pump according to claim 1, characterized in that the at least one switching member comprises at least one solenoid valve (26, 28).

3. Heat pump according to claim 1, characterized in that the sensor (18) for detecting an operating parameter of the heat pump detects the pressure of the refrigerating fluid at the high pressure part of the refrigerating circuit.

4. Heat pump according to claim 1, characterized in that it comprises at least two heat exchange circuits (22) which are disposed in series in the condenser (12).

5. Heat pump according to claim 4, characterized in that it further comprises a branch circuit (24) with respect to one of the heat exchange circuits (22).

6. Heat pump according to claim 1, characterized in that it comprises at least two heat exchange circuits (22) disposed in parallel in the condenser (12).

7. Method for heating swimming pool water by means of a heat pump according to claim 1, characterized in that it comprises:

the measurement of an operating parameter of the heat pump,

the comparison of the measured value of the parameter with a threshold and,

when the parameter exceeds a threshold, the control of the switching of the circulation of the refrigerating fluid in a heat exchange circuit (22).

8. Method according to claim 7, characterized in that the comparison with a threshold comprises the use of two different thresholds, depending on whether the parameter increases or decreases, so that control is obtained with a hysteresis effect.

9. Heat pump according to claim 2, characterized in that the sensor (18) for detecting an operating parameter of the heat pump detects the pressure of the refrigerating fluid at the high pressure part of the refrigerating circuit.

10. Heat pump according to claim 2, characterized in that it comprises at least two heat exchange circuits (22) which are disposed in series in the condenser (12).

11. Heat pump according to claim 3, characterized in that it comprises at least two heat exchange circuits (22) which are disposed in series in the condenser (12).

12. Heat pump according to claim 2, characterized in that it further comprises a branch circuit (24) with respect to one of the heat exchange circuits (22).

13. Heat pump according to claim 3, characterized in that it further comprises a branch circuit (24) with respect to one of the heat exchange circuits (22).