FR3071913A1 - HEAT PUMP AND METHOD OF OPERATION - Google Patents

Abstract

Heat pump system (1) in which the heat pump comprises a thermodynamic heat loop (2) comprising a refrigerant, said thermodynamic loop (2) being provided with a compressor (5), a condenser (6) ), an expander (7) and an evaporator (8), and - a heat transfer loop (3) comprising a coolant identical to the refrigerant, and wherein the evaporator (8) is configured from so that the refrigerant and the coolant are in contact in said evaporator (8) the transfer loop (3) comprising means (10) able to pressurize the coolant at a pressure greater than atmospheric pressure, and the thermodynamic loop (2) comprising means (9) able to maintain the pressure in the thermodynamic loop at a pressure lower than atmospheric pressure, the refrigerant and the coolant being water or water containing an additive.

Description

The present invention relates to a heat pump and its operating method. In particular, the invention relates to a heat pump using water as a refrigerant and its operating method.

Heat pump systems are well known.

These systems are used in many industries where heat exchange is required.

Heat pump systems generally include a thermodynamic heat loop and a heat transfer loop produced in the thermodynamic loop. Heat transfer between the thermodynamic loop and the transfer loop takes place via the evaporator or the condenser. The heat transfer fluid circulates in the transfer loop while the refrigerant circulates in the thermodynamic loop.

Among the heat pump systems are refrigeration systems. In these, the heat transfer between the thermodynamic loop and the transfer loop takes place via the evaporator. These systems use a refrigerant. Various refrigerants can be used.

The refrigerants can be used in their pure state or mixed with other refrigerants depending on the thermodynamic properties sought.

The constant efforts to make the heat pump systems less harmful to the environment have led to experiment with systems of production of cold using water as refrigerant. In fact, conventional heat pump systems using fluids other than water are particularly harmful to the environment.

These systems operate in closed form. Thus the thermodynamic loop and the transfer loop are distinct from each other.

The Applicant has realized that a drawback of these architectures is the poor efficiency of the heat exchange between the thermodynamic sparge and the transfer sparge, to the detriment of the overall efficiency of these cold production systems.

Another drawback of these architectures, in relation to the previous one, lies in the fact that in order to obtain a set temperature of the heat transfer fluid at the outlet of the evaporator in the transfer slurry, a significant amount of energy must be consumed in the thermodynamic plug.

Thus the beneficial effects on the environment obtained by the use of water as a refrigerant are tainted by an excessive consumption of energy in your thermodynamic plug.

In addition, heat pump systems using water as operating fluids may include means for maintaining vacuum. Maintaining a vacuum means that the pressure is lower than atmospheric pressure, particularly inside the thermodynamic loop. These vacuum maintenance systems make the most of the thermodynamic properties of water. However, known vacuum maintenance systems have drawbacks. A first drawback lies in the fact that these systems are not sufficiently reactive. This means that they are not able to recreate the vacuum (pressure below atmospheric pressure) quickly enough, thereby encumbering the efficiency of the heat pump insofar as the thermodynamic properties of the fluid are not fully exploited during a certain period. A second drawback lies in the fact that the known vacuum maintenance systems use particularly energy-consuming technologies.

The invention aims to remedy at least one of these drawbacks.

Thus at least one objective is to improve the overall performance of cold production systems using water as a refrigerant.

To this end, a heat pump system is proposed, in which it comprises:

a thermodynamic heat loop comprising a refrigerant, said thermodynamic loop being provided with a compressor, a condenser, a pressure reducer and an evaporator, and a heat transfer loop comprising a heat transfer fluid identical to the refrigerant , and in which the evaporator is configured so that the refrigerant and the heat transfer fluid are in contact in said evaporator, the transfer loop comprising means capable of pressurizing the heat transfer fluid at a pressure higher than atmospheric pressure, and the thermodynamic loop comprising means capable of maintaining the pressure in the thermodynamic loop at a pressure below atmospheric pressure, the refrigerant and the heat transfer fluid being water or water containing an additive.

Such a device makes it possible to maximize the heat exchange between the thermodynamic loop and the transfer loop allowing better efficiency of the heat pump system.

In particular, maintaining vacuum using the means described above makes it possible to significantly improve the efficiency of the heat pump system.

Various additional characteristics can be provided alone or in combination:

the means capable of extracting inert gases towards the external environment, hereinafter extraction unit, comprise an extraction circuit located upstream of the expansion valve and downstream of the condenser relative to the direction of circulation of the refrigerant;

the extraction unit comprises a fluid valve, an inert gas concentration chamber capable of storing inert gases, an isolation valve capable of isolating the extraction unit from the outside medium and a vacuum pump capable of extracting inert gases to the outside environment;

the extraction unit includes a fluid valve, an inert gas concentration chamber capable of storing inert gases, an isolation valve capable of isolating the extraction unit from the outside environment and a bypass circuit connecting fluid the concentration chamber to the transfer sparge at the outlet of the means capable of pressurizing the heat transfer fluid, the bypass circuit further comprising a bypass valve capable of cutting the bypass circuit;

system comprising a second extraction unit provided with heating means arranged in the evaporator;

the second extraction unit comprises a second extraction circuit, the second extraction circuit comprising means for isolating said second extraction circuit;

system comprising a pressure sensor and a temperature sensor capable of measuring the pressure and the temperature in the concentration chamber;

system comprising a computer unit capable of controlling the compressor, the condenser and the means capable of extracting inert gases to the outside environment.

Secondly, a method of implementing the heat pump system as previously described is proposed, in which it comprises;

a first stage of extraction of the inert gases in the thermodynamic loop, a second stage of production in which the compressor and the fluid circulation pump are started, a third stage of extraction of the inert gases from the thermodynamic loop, this stage being performed during the second stage.

Various additional features can be provided alone or in combination;

the third step is triggered at regular intervals and for a predetermined duration;

the third step is triggered as soon as the computer unit detects that the quantity of inert gases in the concentration chamber reaches a set value;

during the third step, the compressor is activated to accelerate the extraction of inert gases.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example and with reference to the figures in which;

- Figure 1 is a schematic representation of a heat pump system according to the invention;

- Figure 2 is a schematic representation of an extraction unit according to the invention,

FIG. 3 is a schematic representation of an alternative embodiment of the extraction unit,

FIG. 4 is a schematic representation of an alternative embodiment of an extraction unit,

- Figure 5 is a schematic representation of a second extraction unit according to the invention,

- Figure 6 is a schematic representation of a method according to the invention.

In Figure 1 is illustrated a heat pump system 1 configured to produce cold. The heat pump system 1 comprises a thermodynamic heat loop 2 and a heat transfer loop 3 produced by the thermodynamic loop 2. The thermodynamic loop 2 advantageously produces cold. However, it can also produce heat.

The thermodynamic loop 2 includes a refrigerant. This refrigerant circulates in thermodynamic loop 2 in the direction of the arrows 4. Thermodynamic loop 2 includes:

- a compressor 5,

- a condenser 6,

- a regulator 7, and

- an evaporator 8.

The compressor 5 is advantageously of the dynamic type, that is to say that the compression ratio can be modulated. The compressor 5 includes several compression stages and is capable of achieving a compression ratio greater than 2.

The thermodynamic loop 2 comprises means 9 capable of extracting inert gases towards the outside environment.

The transfer loop 3 comprises a heat transfer fluid. The heat transfer fluid is identical to the refrigerant.

The evaporator 8 is configured so that the refrigerant and the heat transfer fluid are in contact in said evaporator 8.

The transfer loop 3 comprises means 10 capable of pressurizing the heat transfer fluid at a pressure greater than atmospheric pressure. These means are for example a fluid circulation pump 10.

The refrigerant and the heat transfer fluid are identical, and are water. Water may contain an additive, for example ethylene glycol. This advantageously makes it possible to lower the solidification temperature of the fluid.

In the following, the architecture of the heat pump system 1 will be described.

The compressor 5 of the thermodynamic loop 2 comprises an inlet 11 compressor and an outlet 12 compressor fluidly connected to the condenser 6 by an inlet 13 condenser. An outlet 14 condenser is fluidly connected to the regulator 7 by an inlet 15 regulator. An expansion valve outlet 16 is fluidly connected to a refrigerant inlet 17 of the evaporator 8. The evaporator 8 comprises a refrigerant outlet 18 fluidly connected to the compressor inlet 11.

The transfer loop 3 is partially represented in FIG. 1, this comprises an inlet fluid circuit 19 comprising a device generating a pressure drop, for example a diaphragm 20 and an outlet fluid circuit 21 comprising the pump 10 traffic. The inlet fluid circuit 19 is fluidly connected to an inlet 22 for the heat transfer fluid of the evaporator 8. The outlet fluid circuit 21 is fluidly connected to an outlet 23 for the heat transfer fluid from the evaporator 8.

The means 9 capable of extracting inert gases towards the external environment, hereinafter called the extraction unit 9, are advantageously located downstream of the condenser 6 and upstream of the expansion valve 7 with respect to the direction of circulation of the refrigerant in the vicinity of a high point, that is to say of a point located most in height. In fact, non-condensable gases tend to accumulate there.

In the embodiment shown in FIG. 2, the extraction unit 9 comprises an extraction circuit 24 comprising a fluid valve 25 followed by a chamber 26 for concentrating the inert gases followed by an isolation valve 27 then a vacuum pump 28. The extraction circuit 24 overlooks the outside environment. The vacuum pump 28 allows suction from the thermodynamic loop 2 to the outside environment. The isolation valve 27 isolates the thermodynamic loop 2 from the outside environment.

In an alternative embodiment illustrated in FIG. 3, the vacuum pump 28 is followed by the isolation valve 27 according to the direction of circulation of the fluid represented by arrows 4.

The isolation valve 27 can be opened and closed manually or by a controlled actuator not shown in the figures.

In an alternative embodiment shown in FIG. 4, the heat pump system 1 comprises an extraction unit 9 situated upstream from the pressure reducer 7 and overlooking the external environment. The extraction circuit 24 comprises a fluidic valve 25 followed by a concentration chamber 26 followed by an isolation valve 27. In this embodiment, the extraction circuit 24 comprises a bypass circuit 29 fluidly connecting the concentration chamber 26 to the transfer loop 3 at the outlet of the fluid circulation pump 10. The bypass circuit 29 includes a bypass valve 30 for cutting the bypass circuit.

The extraction unit 9 has the advantage of allowing a vacuum, that is to say a pressure lower than atmospheric pressure in the thermodynamic loop 2, quickly. Indeed, when it is deemed necessary to lower the pressure in the thermodynamic loop 2, the extraction unit 9 makes it possible to quickly recreate the vacuum.

Advantageously, the heat pump system 1 can comprise additional means for extracting inert gases. Thus the device can include a second extraction unit 31. The second extraction unit 31 comprises heating means 32, for example an electric heating resistor 32, arranged in the evaporator 8. The second extraction unit 31 uses the extraction circuit 24. In the variant embodiment shown in FIG. 4, the extraction circuit 24 comprises isolation means, for example a non-return valve 34.

As a variant, the second extraction unit 31 may comprise a second extraction circuit 33 separate from the circuit 24, The second extraction circuit 33 comprises the isolation means, for example the non-return valve 34. When the second unit 31 of extraction comprises a second extraction circuit 33 separate from the extraction circuit 24, this second extraction unit 31 can be implemented in the embodiments of FIGS. 2 and 3.

The condenser 6 is cooled by air or hydraulic cooling.

Advantageously, the system 1 comprises a pressure sensor 35 and a temperature sensor 36 capable of measuring the pressure and the temperature in the concentration chamber 26. These sensors 35, 36 make it possible to determine the quantity of inert gases in the concentration chamber 26.

Advantageously, the system 1 comprises an evaporator temperature sensor 37 located in a lower part 38 of the evaporator 8 and an evaporator pressure sensor 39 located in an upper part 40 of the evaporator 8. The evaporator temperature sensor 37 makes it possible to provide the temperature information necessary to modulate the speed of the fluid circulation pump 10 as a function of the temperature available in the evaporator 8. The evaporator pressure sensor 39 makes it possible to modulate the speed of the compressor 5.

In the following, the operation of the heat pump system 1 will be described.

An operating method of the heat pump system 1 comprises a first step 41 of extraction of the inert gases in the thermodynamic loop 2. This first step 41 is carried out at the start of the system 1. In particular, the first step 41 is carried out after the first start-up or after a long shutdown of the system 1, for example after a maintenance operation requiring the shutdown of the system 1 .

The first step 41 is carried out by the second extraction unit 31 shown in FIG. 5, before the production system starts up, the electrical resistor 32 is switched on and the liquid from the evaporator 8 is brought to the boil. The steam generated in the evaporator 8 puts the thermodynamic loop 2 under pressure. When the pressure is high enough to open the non-return valve 34, (the inert gases are evacuated to the outside environment at the same time as the refrigerant. Pure vapor will then gradually occupy the entire thermodynamic loop 2. In order to speed up the extraction of inert gases, the compressor 5 can be used.

The method comprises a second step 42 called production. In this production step 42 the compressor 5 and the circulation pump 10 are started. In the inlet fluid circuit 19, the heat transfer fluid passes through the device generating a pressure drop, for example the diaphragm 20, a pressure drop ensues allowing the heat transfer fluid to evaporate instantly at the inlet of the 'evaporator

8.

The steam generated in the evaporator 8 is compressed by the compressor

5. The pressure at the outlet of the compressor is lower than atmospheric pressure, The pressure value depends on the use made of the thermodynamic loop 2. For example, the pressure can be 50 mbar. The vapor is then sent to the condenser 6 where it is cooled so as to condense. At the outlet of the condenser 6, the refrigerant is in the liquid state.

The refrigerant in the liquid state then passes through the regulator 7 where it loses pressure. The drop in pressure is accompanied by a further drop in the temperature of the refrigerant. Partial evaporation then occurs and the refrigerant then has two phases, a cold liquid phase and a cold gas phase. In thermodynamic loop 2 the pressure is constantly lower than atmospheric pressure.

The refrigerant then enters the evaporator 8. The gas phase joins the thermodynamic loop 2 in its upper part 40 of the evaporator 8. The cold liquid phase falls by gravity into the lower part 38 of the evaporator. The cold liquid phase is then sent to the fluidic circuit 21 of the transfer loop 3 output to be used.

The thermodynamic loop 2 and the transfer loop 3 may have leaks. Inert gases, that is to say that do not have thermodynamic properties which can be exploited in the context of the production of heat (hot or cold), contaminate the refrigerants and heat transfer fluids, which affects the efficiency of thermodynamic loop 2.

Thus, the method comprises a third step 43 of extracting the inert gases and maintaining a vacuum. Maintaining a vacuum consists in maintaining the pressure in the thermodynamic loop 2 at a pressure below atmospheric pressure. The third step 43 consists in extracting the inert gases from the thermodynamic loop 2 during operation, that is to say during the second step 42.

The inert gases are stored in the concentration chamber 26. The third step 43 uses the extraction unit 9. Referring to Figures 2 and 3, the fluid valve 25 is closed and the isolation valve 27 is open. The vacuum pump 28 operates and extracts the inert gases to the outside environment. When the concentration chamber 26 no longer contains inert gases, the vacuum pump 28 is stopped and the isolation and fluidic valves 25, 27 are closed and open respectively.

In the extraction unit 9 shown in FIG. 4, the extraction of inert gases is done differently. The fluid valve 25 is closed and the isolation and bypass valves 27.30 are open. The circulation pump 10 then sends heat transfer fluid to the concentration chamber 26, ejecting the inert gases towards the outside environment. When the concentration chamber 26 no longer contains inert gases, the isolation and bypass valves 27, 30 are closed, the fluid valve 25 is open.

The method is implemented by means of a control unit 44. Thus, the heat pump system 1 comprises a control unit 44. The computer control unit 44 controls in particular the compressor 5 and the circulation pump 10 as well as the various valves 25, 27, 30 and the vacuum pump 28. The unit 44 also controls the heating means 32 and the pressure reducer 7. When the cooling is aeraulic in the condenser 6, the unit 44 also controls the aeraulic cooling means. The control unit 44 receives the temperature and pressure values from the sensors 35, 36, 37, 39, temperature and pressure.

The third step 43 can be launched at regular intervals and for a certain duration. In a variant, the third step can be launched when the computer unit 44 detects a target volume of inert gases in the concentration chamber 26, by virtue of the temperature and pressure sensors 35, 36 capable of measuring the temperature and the pressure in the concentration chamber 26. Indeed, when the thermodynamic loop 2 is not contaminated by inert gases, the concentration chamber 26 is filled with refrigerant. When there is contamination, your inert gases gradually replace the refrigerant in the concentration chamber 26.

A first advantage of the production system 1 and of the method described above is that it makes it possible to increase the efficiency of the heat exchange between the thermodynamic loop 2 and the transfer loop 3 for the benefit of a significant improvement in the overall efficiency. of production system 1.

Another advantage, in relation to the previous one, is that to obtain a set temperature of the heat transfer fluid at the outlet of the evaporator 8 in the transfer loop 3, a lesser amount of energy is consumed.

Another advantage conferred by the production system 1 and the process is that it has a less harmful impact on the environment.

i5

Another advantage of the system 1 is that it makes it possible to carry out the evacuation and maintenance of the vacuum efficiently and without adding complex and bulky systems.

Claims (12)

1. Heat pump system (1) characterized in that it comprises: a thermodynamic heat loop (2) comprising a refrigerant, said thermodynamic loop (2) being provided with a compressor (5), a condenser (6), a pressure reducer (7) and an evaporator ( 8), and a heat transfer loop (3) comprising a heat transfer fluid identical to the refrigerant, and in that the evaporator (8) is configured so that the refrigerant and the heat transfer fluid are in contact in said evaporator (8), the transfer loop (3) comprising means (10) capable of pressurizing the heat transfer fluid at a pressure higher than atmospheric pressure, and the thermodynamic loop (2) comprising means (9) capable of maintaining the pressure in the thermodynamic loop at a pressure below atmospheric pressure, the refrigerant and the heat transfer fluid being water or water containing an additive. 2. A heat pump system (1) according to claim 1 characterized in that the means (9) capable of extracting inert gases towards the external medium, hereinafter extraction unit (9), comprise a circuit (24 ) extraction located upstream of the expansion valve (7) and downstream of the condenser (6) relative to the direction of circulation of the refrigerant. 3. System (1) heat pump according to claim 2 characterized in that the extraction unit (9) comprises a fluid valve (25), a chamber (26) for concentrating inert gases capable of storing gases inert, an isolation valve (27) capable of isolating the unit (9) for extracting the external medium and a vacuum pump (28) capable of extracting the inert gases towards the external medium. 4. Heat pump system (1) according to claim 2 characterized in that the extraction unit (9) comprises a fluid valve (25), a chamber (26) for concentrating inert gases capable of storing gases inert, an isolation valve (27) capable of isolating (the unit (9) for extracting the external medium and a bypass circuit (29) fluidly connecting the concentration chamber (26) to the loop (3) transfer at the outlet of the means (10) able to pressurize the heat transfer fluid, the bypass circuit (29) further comprising a bypass valve (30) capable of cutting the bypass circuit (29), 5. System (1) heat pump according to one of claims 2 to 4 characterized in that it comprises a second extraction unit (31) provided with heating means (32) arranged in the evaporator ( 8). 6. A heat pump system (1) according to claim 5 characterized in that the second extraction unit (31) comprises a second extraction circuit (33), the second extraction circuit (33) comprising means (34) for isolating said second extraction circuit (33). 7. A heat pump system (1) according to one of claims 3 to 6 characterized in that it comprises a pressure sensor (35) and a temperature sensor (36) capable of measuring the pressure and the temperature in the concentration chamber (26). 8. Heat pump system (1) according to one of the preceding claims, characterized in that it comprises a computer unit (44) capable of controlling the compressor (5), the condenser (6) and the means (9 ) able to extract inert gases to the outside environment. 9. A method of implementing the system (1) heat pump according to one of the preceding claims characterized in that it comprises; a first step (41) of extraction of the inert gases in the thermodynamic loop, a second step (42) of production in which the compressor (5) and the pump (10) for fluid circulation are started, a third step ( 43) for extracting the inert gases from the thermodynamic loop (2), this step being carried out during the second step (42). 10. Method according to claim 9 characterized in that the third step (43) is triggered at regular intervals and for a predetermined duration. 11. Method according to claim 9 characterized in that your third step (43) is triggered as soon as the computer unit (44) detects that the quantity of inert gases in the concentration chamber (26) reaches a set value. 12. Method according to any one of claims 9 to 11 wherein during the third step (43), the compressor (5) is operated to accelerate the extraction of inert gases.