DE102020122713A1 - Heat pump and method for operating a heat pump - Google Patents

Abstract

The present invention relates to a heat pump and a method for operating a heat pump. According to the invention, a target value for optimized hot gas overheating is defined as a function of a heat source temperature and a required flow temperature. The instantaneous hot gas superheat is determined from the difference between a temperature determined from the pressure (P2) in the high pressure or hot gas section of the refrigerant circuit and a temperature determined from the pressure (P1) in the low pressure or suction gas section of the refrigerant circuit, and the expansion valve (4) so controlled so that the hot gas superheat approaches the target value.

Description

The present invention relates to a compression heat pump or a refrigerating machine according to claim 1 and a method for operating such according to claim 11.

In a compression heat pump, a refrigerant is compressed using a mechanical compressor (preferably driven by an electric motor) and moved through a cyclic process. A compression heat pump can also be operated as a refrigerating machine, but in the following, for the sake of simplicity, the term "compression heat pump" or just "heat pump" is usually used, without this being understood as a limitation.

A compression heat pump according to the preamble of claim 1 has a refrigerant circuit which includes an evaporator, a compressor, a condenser and a controllable expansion valve. The controllable expansion valve is controlled by a control device. A first pressure sensor is provided for detecting a pressure in a high pressure or hot gas section of the refrigerant circuit.

A generic compression heat pump is from EP 0 866 291 B1 famous. In the compression heat pump disclosed in this document, a second sensor is provided to regulate the expansion valve in addition to a temperature sensor arranged in a first area between the compressor and the condenser, which sensor detects a pressure that represents a direct measure of the condensation pressure and the condensation temperature. In the following, a direct measure of the condensation temperature is understood to mean that, with a given operational arrangement, at least an approximate condensation temperature can be determined from a value detected by a sensor without consulting other measured variables reflecting the current state of the system. In the EP 0 866 291 B1 Therefore, a method for operating such a compression heat pump is disclosed, in which the expansion valve is controlled based on the pressure or the temperature in the high-pressure or hot-gas section of the refrigerant circuit. From this pressure, a condensation temperature is determined, which is used to regulate the heat pump.

The function of such a generic, known heat pump is briefly described below and the terms used are explained. The high-pressure section of the refrigerant cycle, also called the hot-gas section of the refrigerant cycle, is the area of a compression heat pump where the refrigerant (a refrigerant vapor or a mixture of liquid refrigerant and refrigerant vapor, or generally a refrigerant fluid) resides in an area between the compressor and the expansion valve , i.e. in an area of increased pressure. The term "hot gas section" follows from the increased temperature of the refrigerant after compression by the compressor. A low-pressure section or suction gas section of the refrigerant circuit, on the other hand, is the remaining section of the refrigerant circuit between the expansion valve and the compressor, since the refrigerant is moved here under reduced pressure and reduced temperature after expansion through the expansion valve. The term "suction gas section" results from the fact that the refrigerant in this section of the refrigerant circuit is sucked in by the compressor and compressed towards the high-pressure or hot gas section. During cooling in the condenser, condensation heat is extracted from the refrigerant by the heat exchanger function of the condenser and fed to a consumer.

A disadvantage of known compression heat pumps and methods for operating such compression heat pumps is the fact that the compression heat pumps are only optimally regulated with regard to specific operating points. In the case of a geothermal heat pump in which an evaporator is positioned at a depth of 30 cm below the frost level, ie typically 1.20 m deep in the ground, an evaporation temperature of 3°C is assumed, for example. In the case of a compression heat pump with a geothermal probe, which is typically drilled to a depth of 100 m, an evaporation temperature of +5°C can be assumed, for example. Corresponding geothermal heat pumps have a brine circuit, by means of which the heat is absorbed from the ground and released into the evaporator to the refrigerant circuit by evaporating the expanded refrigerant.

Assuming a constant temperature of the heat source, which also approximates the evaporation temperature of the refrigerant, the efficiency of the compression heat pump can be reduced if there is a deviation from this assumed temperature, since its control is then not only optimal.

A seasonal fluctuation in the ambient temperature also means that known compression heat pumps are often no longer optimally controlled. Since, when outside temperatures are cold, significantly more energy is required to heat radiators or underfloor heating in addition to the energy required to prepare hot water, a comparatively high flow temperature is required at which the water from the condenser (heated by this in the heat exchange with the refrigerant) is fed to a consumer will. Correspondingly required flow temperatures can therefore lie in a wide range of, for example, 25°C to 65°C (higher when using radiators than with underfloor heating).

The problem is even greater with air heat pumps, in which heat is extracted from the ambient air and fed to the consumer. Depending on the season, the evaporation temperatures can vary within a range of -30°C to +25°C.

The large ranges of evaporation temperatures that occur (which approximately correspond to the temperature of the heat source) and condensation temperatures (which approximately correspond to the flow temperatures) mean that known heat pumps, in which, for example, only the hot gas or condensation temperature are used to control the compression heat pump, comparatively often in areas by not providing good efficiency. There is no guarantee that the heat pump will operate with the best possible efficiency at different temperatures and pressures in the low-pressure and high-pressure sections.

It is therefore the object of the present invention to provide a compression heat pump and a method for operating a compression heat pump in which the efficiency is improved. It is also an object of the invention to provide a method for operating such a compression heat pump, which also increases the efficiency of the compression heat pump.

According to the invention, this object is achieved by a compression heat pump according to the characterizing part of claim 1 and by a method for operating a compression heat pump according to claim 11.

In a compression heat pump according to the characterizing part of claim 1, in addition to the first pressure sensor for detecting a pressure P2 in a high-pressure or hot gas section of the refrigerant circuit as a measure of the condensation pressure and the condensation temperature according to the invention, a second pressure sensor is provided for detecting a pressure P1 in a low pressure - or suction gas section of the refrigerant circuit. This pressure P1 is a direct measure of the evaporation pressure and the evaporation temperature.

A compression heat pump according to the invention offers the advantage that the control device can take into account not only the pressure P2 in the high-pressure section of the refrigerant circuit, but also this pressure P1 in the low-pressure section of the refrigerant circuit.

In a method according to the invention as claimed in claim 11, a target value for optimized hot gas overheating is defined as a function of the heat source temperature or the evaporation temperature and the required flow temperature or the condensation temperature.

The instantaneous hot gas overheating can then be calculated from the difference between a temperature determined from the pressure (P2) or a measured temperature (T1) in the high-pressure or hot gas section of the refrigerant circuit and a temperature determined from the pressure (P1) or a measured temperature (T2) in the Low-pressure or suction gas section of the refrigerant circuit can be determined (the temperatures T1 and T2 can thus be determined from the pressures P2 and P1 or measured using separate temperature sensors).

In a third step, the expansion valve is controlled in such a way that the hot gas overheating approaches the target value.

Within the scope of the invention, it was found that for different outside temperatures and different flow temperatures, hot gas overheating can be determined at which the efficiency of a compression heat pump is optimal. A deviation from this hot gas overheating therefore leads to poorer efficiency.

After this was recognized, different hot gas overheating was set for different (simulated) outside temperatures in a test heat pump and the efficiency of the heat pump was determined. Hot gas overheating is the temperature increase that occurs as a result of the compression of the refrigerant, i.e. the temperature difference between the refrigerant before and after the compressor. With regard to the outside temperature, it can be assumed that this also approximately corresponds to the evaporation temperature of the refrigerant in the evaporator. This evaporation temperature can be measured directly by a temperature sensor or calculated using a determined pressure (pressure sensor). It is true that measuring with a temperature sensor is cheaper, since temperature sensors are cheaper to manufacture and install than pressure sensors. However, pressure sensors offer the advantage that their measurements are less error-prone. In the case of temperature sensors in particular, it is problematic that the thermal contact with the refrigerant is not always so reliable that precise measurements are possible.

The outside temperatures can be simulated by specifying the appropriate temperature on the evaporator using a heating and/or cooling element. The hot gas overheating was varied through different settings of the expansion valve. The efficiency of the heat pump was then determined for various hot gas overheating conditions. The efficiency of a heat pump is the ratio of heat energy obtained to the energy supplied to the heat pump. The energy supplied to the heat pump is essentially the electrical energy that has to be supplied to the compressor in order to maintain the refrigerant cycle.

Two tables are used below to show how the increase in efficiency of a heat pump according to the invention is achieved compared to known heat pumps.

Table 1 shows the increase in efficiency for various hot gas overheating conditions at an outside temperature of -7°C and a flow temperature of 35°C. Table 2 shows the increase in efficiency for an outside temperature of 0°C and a desired flow temperature of 30°C as a function of different hot gas overheating levels. Both tables make it clear that there is an optimal operating point for the heat pump at which the increase in efficiency is maximum.

The optimum operating point also depends on the outside temperature and the flow temperature. While at an outside temperature of -7°C the maximum efficiency is at a hot gas overheating of approx. 37 K, at an outside temperature of 0°C an optimal operating point of the compression heat pump is reached at a hot gas overheating of approx. 22 K.

Precisely this knowledge, namely the fact that for different outside temperatures and for different flow temperatures a maximum efficiency of the compression heat pump results with optimal hot gas overheating, is taken into account in the design of the compression heat pump according to the characterizing part of claim 1 and in the method according to the invention according to claim 11 .

The fact that a second pressure sensor for detecting the pressure P1 in the low-pressure or suction gas section is provided in addition to the first pressure sensor for detecting the pressure P2 in the high-pressure or hot gas section of the refrigerant circuit means that the hot gas overheating can be determined and can also be determined more precisely than when using only two pure temperature sensors.

In the method according to claim 11 according to the invention, it is accordingly taken into account that a target value for the optimized hot gas overheating is defined for a specific heat source temperature, the hot gas overheating is measured and the expansion valve is readjusted so that the hot gas overheating approaches the target value.

Preferred configurations of the invention result from the dependent claims.

The second pressure sensor is preferably arranged between the evaporator and the compressor.
A temperature sensor for detecting a temperature T2 can be provided in the low-pressure or suction gas section of the refrigerant circuit, in particular between the evaporator and the compressor.
Furthermore, the first pressure sensor is preferably arranged between the condenser and the expansion valve, particularly preferably between the condenser and a subcooler.
In a further preferred embodiment of the invention, the first pressure sensor is arranged on a refrigerant collector.
A further temperature sensor can be provided for detecting a temperature T1 in the high-pressure or hot-gas section of the refrigerant circuit and can preferably be arranged between the compressor and the condenser.

The first pressure sensor is preferably arranged on a refrigerant collector. A variant with an overheating heat exchanger between the condenser or a sub-cooler arranged downstream of the condenser and the expansion valve for heat exchange between the refrigerant flowing towards the evaporator and flowing away from it towards the compressor is particularly preferred.

The compression heat pump can in particular be an air heat pump that extracts heat from the ambient air and supplies it to a consumer.

1. i. In Abhängigkeit von der Wärmequellentemperatur oder der Verdampfungstemperatur und der benötigten Vorlauftemperatur oder der Kondensationstemperatur ein Zielwert für eine optimierte Heißgasüberhitzung festgelegt,
2. ii. die momentane Heißgasüberhitzung aus der Differenz zwischen einer aus dem Druck (P2) ermittelten Temperatur oder einer gemessenen Temperatur (T1) im Hochdruck- oder Heißgasabschnitt des Kältemittelkreislaufs und einer aus dem Druck (P1) ermittelten Temperatur oder einer gemessenen Temperatur (T2) im Niederdruck- oder Sauggasabschnitt des Kältemittelkreislaufs ermittelt,
3. iii. das Expansionsventil (4) so geregelt wird, dass sich die Heißgasüberhitzung dem Zielwert annähert.

In a method according to the invention for operating a compression heat pump or a compression refrigeration machine according to one of the preceding claims

1. i. Depending on the heat source temperature or the evaporation temperature and the required flow temperature or the condensation temperature, a target value for optimized hot gas overheating is specified,
2. ii. the instantaneous hot-gas superheat from the difference between a temperature determined from the pressure (P2) or a measured temperature (T1) in the high-pressure or hot-gas section of the refrigerant circuit and a temperature determined from the pressure (P1) or a measured temperature (T2) in the low-pressure section or suction gas section of the refrigerant circuit is determined,
3. iii. the expansion valve (4) is controlled in such a way that the hot gas superheat approaches the target value.

1. i. bei einer im Vergleich zum Zielwert zu geringen Heißgasüberhitzung das Expansionsventil (4) weiter geschlossen wird,
2. ii. bei einer im Vergleich zum Zielwert zu großen Heißgasüberhitzung das Expansionsventil (4) weiter geöffnet wird.

In particular, it can be provided that:

1. i. if the hot gas overheating is too low compared to the target value, the expansion valve (4) is closed further,
2. ii. the expansion valve (4) is opened further if the hot gas overheating is too high compared to the target value.

The target value preferably represents the value of an optimized efficiency of the compression heat pump.
In a further preferred embodiment of the invention, target values specified for different heat source temperatures and/or for different flow temperatures are stored in tabular form in a control device of the compression heat pump.
The target values for different heat source temperatures and/or for different flow temperatures are preferably determined from measurements of the efficiency of the heat pump as a function of the hot gas overheating at the different heat source temperatures before being stored in tabular form.
A target value for a heat source temperature can be determined from efficiency measurements measuring the hot gas superheat in increments of 5k to 15K over a range from a minimum hot gas superheat of 10K to 30K to a maximum hot gas superheat of 35K to 80K, and the hot gas superheat with maximum efficiency is stored as the target value for this heat source temperature.
The temperature determined from the pressure (P1) or the temperature measured (T2) in the low-pressure or suction gas section of the refrigerant circuit can be used as an approximate heat source temperature.
Preferably, for a heat source temperature in a range from -10 ° C to
-5°C a target value for the hot gas superheat is set in a range from 32K to 42K, preferably from 35K to 40K.
For a heat source temperature in a range from -5°C to +5°C, a target value for the hot gas superheat can be set in a range from 17K to 27K, preferably from 19K to 25K.

• 1 eine erfindungsgemäße Kompressionswärmepumpe;
• 2 eine weitere Ausführungsform einer erfindungsgemäßen Kompressionswärmepumpe; und
• 3 eine dritte Ausführungsform einer erfindungsgemäßen Kompressionswärmepumpe.

The invention is based on the 1 until 3 explained in more detail as an example. It shows:

• 1 a compression heat pump according to the invention;
• 2 a further embodiment of a compression heat pump according to the invention; and
• 3 a third embodiment of a compression heat pump according to the invention.

1 shows a compression heat pump according to the invention in a schematic representation. A refrigerant fluid, ie a vapor or a liquid or a vapor/liquid mixture of a fluid, is conducted through a cyclic process by means of the compression heat pump shown. Here, the refrigerant is compressed by means of a compressor 6, thereby increasing its temperature and pressure. A high-pressure section or hot-gas section of the refrigerant circuit is therefore formed downstream of the compressor. A temperature sensor 20 is provided in this high-pressure section to measure the temperature T1 of the compressed refrigerant.

Downstream of the compressor 6, the refrigerant is then conducted into a condenser 1, which is a heat exchanger and serves to condense the compressed, vaporous refrigerant. Condensation heat is removed from the refrigerant and a not shown Ver needer fed via a partially shown consumer circuit 23 with a flow 21 and a return 23.

A refrigerant collector 2 which temporarily stores refrigerant is arranged downstream of the condenser 1 . The refrigerant collector 2 thus serves as a buffer for the refrigerant. The pressure P2 of the refrigerant in the refrigerant collector 2 is determined via a first pressure sensor 19 . This pressure P2 also corresponds to the condensation pressure of the refrigerant in the condenser 1 and further reflects the condensation temperature in the condenser 1, which means that the condensation temperature in the condenser 1 can be calculated from the pressure P2.

A subcooler 3 is arranged downstream of the refrigerant collector 2 , through which refrigerant exiting from the refrigerant collector 2 flows to an expansion valve 4 . The return flow 22 , which flows in the opposite direction through the subcooler 3 to the condenser 1 , is guided through the subcooler 3 , which is designed as a heat exchanger. The combination of refrigerant collector 2 and subcooler 3 improves the cooling capacity of the heat pump, ie increases the heat that the heat pump can transport to the consumer. The sub-cooler 3 serves to preheat the consumer circuit 23. On the other hand, the sub-cooler 3 also leads to the fact that less gaseous refrigerant arrives at the expansion valve 4 as a result of further heat dissipation of the refrigerant.

The refrigerant is expanded and thus cooled by means of the expansion valve 4 . The controlled expansion valve 4 is controlled by a control device, not shown.

After expansion in the expansion valve 4, the still liquid refrigerant is fed to an evaporator 5, which is designed as a heat exchanger and is in thermal contact with a heat source, for example with the ambient air or with the ground. As a result of the heat absorption, the refrigerant evaporates or the remaining liquid components of the refrigerant evaporate and the refrigerant is fed out of the evaporator 5 to the compressor 6, as a result of which the refrigerant circuit is closed.

A second pressure sensor 17 is arranged between the evaporator 5 and the compressor 6 for detecting a pressure P1 in the low-pressure or suction gas section of the refrigerant circuit, the pressure P1 corresponding to the evaporation pressure in the evaporator 5 and being able to be converted into a corresponding evaporation temperature. Another optional temperature sensor 18 is provided for the direct detection of the temperature T2 of the low-pressure section.

The method according to the invention, already explained above, for operating such a compression heat pump can be carried out with the aid of the various sensors or feelers of the heat pump.

First, the evaporation temperature is determined or (as an approximation) the temperature T2 in the low-pressure section of the refrigerant circuit. This can be done either via the temperature sensor 18 or alternatively and more precisely by means of the second pressure sensor 17 by detecting the pressure P1 in the low-pressure section of the refrigerant circuit and determining the temperature which corresponds to the temperature of the refrigerant at this pressure P1.

Depending on this heat source temperature, an optimized hot gas overheating is determined by determining the respective hot gas overheating with maximum efficiency from efficiency curves, as shown in Tables 1 and 2. The actual instantaneous hot gas superheat is then determined from the difference between the temperature corresponding to pressure P2 (or measured temperature T1) in the high-pressure section of the refrigerant circuit and the temperature corresponding to pressure P1 (or measured temperature T2) in the low-pressure section of the refrigerant circuit. The expansion valve 4 is then controlled in such a way that the hot gas overheating approaches the target value, with the expansion valve 4 being closed further if the hot gas overheating is too low compared to the target value and the expansion valve is opened further if the hot gas overheating is too high compared to the target value.

As already explained, the use of pressure sensors 17 and 19 for regulation offers advantages over the use of temperature sensors 18 and 20, since the thermal coupling of a temperature sensor to the refrigerant circuit is more problematic than the connection of a pressure sensor. It has been found that the use of pressure sensors is particularly stable over the long term. However, it can be advantageous for operating a method according to the invention, at least in certain process sections, to use the control of the expansion valve 4 on the temperature sensor 18 in order to To determine temperature T2 instead of determining this temperature using the pressure sensor 17 (pressure P1). In particular in a start-up phase of the heat pump, no stable pressure P1 forms in this start-up phase, which can be used for the regulation described. Therefore, it can make sense in a start-up phase of the compression heat pump to first use the data from the temperature sensor 18 (and possibly also from the temperature sensor 20) to determine the hot gas overheating and only after this start-up phase has expired, for example after 60 seconds, to the pressure data of the pressure sensor 17 (and possibly also the pressure sensor 19) to resort to control.

In the 2 an alternative embodiment of a compression heat pump according to the invention is shown. The already based on the embodiment of 1 explained elements of the compression heat pump and the process steps discussed there are analogous to the embodiment of 2 used. In contrast to the embodiment of 1 However, another heat exchanger is provided here in the form of the overheating heat exchanger 9 for the refrigerant. The compressed and liquefied refrigerant from the sub-cooler 3 flows away from the sub-cooler 3 through the overheating heat exchanger 9 and then on to the expansion valve 4. The refrigerant flows from the evaporator 5 in the embodiment of FIG 2 also on the way to the compressor 6 through the overheating heat exchanger 9 and is thus in heat exchange with the refrigerant flowing to the expansion valve 4 .

Due to the typically very low boiling point of a refrigerant, sub-zero temperatures are sufficient for evaporation. However, it is very important that the refrigerant vapor after leaving the evaporator 5 is heated above its evaporation temperature (overheating or suction gas overheating) so that no liquid refrigerant can get into the compressor 6 . Otherwise so-called liquid hammer could damage the compressor 6 . On the other hand, after the condenser 1 and after the subcooler 3, before the expansion valve 4, the refrigerant is cooled below the condensation temperature (subcooling) in order to avoid the formation of vapor bubbles, which could impair the function of the expansion valve 4 and thus reduce the performance of the heat pump cycle.

3 shows a further embodiment of a heat pump according to the invention. Compared to the embodiments of 1 and 2 is the heat pump 3 supplemented with additional elements. Same elements as in the 1 and 2 are provided with the same reference numbers. In the embodiment of 3 After compression by the compressor 6, the refrigerant is first routed to a four-way switch valve 16 and, in a first position of the four-way switch valve 16, to the condenser 1 and further on through a check valve 13 to the refrigerant collector 2. After the refrigerant collector 2, the refrigerant continues through a subcooler 3 to a superheat heat exchanger 9 and through the expansion valve 4 into the evaporator 5. The refrigerant is in turn fed from the evaporator 5 to the compressor 6 through the four-way switching valve 16 . A gas/liquid separator 8 , through which the refrigerant flows before it is conducted through the overheating heat exchanger 9 into a liquid separator 11 , is also arranged on this section between the four-way switching valve 16 and the compressor 6 . The liquid separator 11 prevents liquid portions of the refrigerant from entering the compressor 6 . Corresponding liquid components can be successively evaporated in the liquid absorber 11 .

In this previously explained first position of the four-way switching valve, the circuit of the refrigerant thus essentially corresponds to that of the embodiment of FIG 2 and thus represents regular heat pump operation.

Alternatively, the four-way switching valve 16 can also be brought into a second position in which the refrigerant circuit is reversed. In this cycle reversal, evaporator 5 becomes the condenser and condenser 1 becomes the evaporator. To distinguish this direction of flow are in the 3 Directional arrows for the direction of flow in heat pump operation indicated and directional arrows in brackets for operation with circuit reversal.

With this circuit reversal, the heat pump can be converted into an air conditioner, by means of which the consumer coupled to the flow 21 and the return 22 can be cooled instead of heated. Another use of such a reversal can be to provide efficient defrosting of the system. In the case of an air heat pump in particular, icing can occur in the area of the evaporator 5 at low outside temperatures, which significantly reduces the efficiency of the heat pump. Here, too, a reversal of the refrigerant circuit can be switched on in order to achieve defrosting of the evaporator 5 .

To reverse the refrigerant circuit, the four-way reversing valve 16 is consequently brought into a second position, with which the refrigerant flow is not routed from the evaporator 5 to the condenser, but vice versa from the condenser to the evaporator 5. While the refrigerant flow is on this first path through the four-way reversing valve 16 is thus reversed in this operating mode, the refrigerant flow remains unchanged on the second path through the four-way switching valve 16 from the compressor 6 in the direction of the overheating heat exchanger 9 compared to the regular heat pump operation.

As already explained, the refrigerant from the evaporator 5 is conducted further in the direction of the condenser 1 in the defrost or air conditioning mode with reverse circulation. The refrigerant is guided through a check valve 15 in an additional section of the refrigerant circuit, which is parallel to the section with the expansion valve 4, through which the refrigerant flows in heat pump operation. After flowing through the non-return valve 15 to the condenser 1, the refrigerant also passes through an expansion valve 12, through which the refrigerant flows only in this defrosting/cooling mode, before it flows through the condenser 1 and then in an opposite direction compared to heat pump operation through the pipeline between Capacitor and four-way switching valve 16 is guided to the four-way switching valve 16.

In addition to this additional option of a possible cycle reversal for a defrost or cooling / air conditioning mode is in the embodiment of 3 opposite of 2 yet another additional line section is inserted, which has an ejector 10 . The line from the overheating heat exchanger 9 to the evaporator 5 branches out here before the expansion valve 4 into a parallel line in which an expansion valve ejector 7 is first inserted, which is followed downstream by the actual ejector 10 and further downstream by a further check valve 14 before the parallel lines of the two expansion valves 4 and 7 are brought together again. The ejector 10 has three connections, one of which is associated with the expansion valve ejector 7 and another with the check valve 14, so that the flow of refrigerant parallel to the pipeline with the expansion valve 4 is guided through these two connections. A third port connects the ejector 10 to the gas-liquid separator 8. As shown in FIG 3 indicated schematically, the inlet of the section from the gas-liquid separator 8 to the ejector 10 is actually aligned perpendicularly to the direction of flow through the ejector from the expansion valve 7 to the check valve 14 .

The ejector 10 serves to increase the efficiency of the heat pump as follows. The ejector 10 utilizes the expansion work present in the refrigerant downstream of the condenser 1 in order to draw in a partial mass flow and convey it to a higher level. Suction takes place via the third port, with which the ejector 10 communicates with the gas-liquid separator 8 . According to the Venturi principle, the gaseous refrigerant flowing through the ejector 10, which is introduced into the ejector from the expansion valve ejector 7, ensures that gaseous refrigerant is sucked out of the gas-liquid separator 8. Therefore, refrigerant from the low-pressure section of the refrigerant circuit is raised to a higher pressure level, bypassing the compressor 6, as a result of which the compressor 6 is relieved and less electrical energy has to be added to the compressor 6. This results in an improved efficiency of the heat pump, i.e. a reduction in the electrical energy invested to obtain a specified heat energy.

Reference List

1

capacitor

2

refrigerant collector

3

subcooler

4

expansion valve

5

Evaporator

6

compressor

7

Expansion valve ejector

8th

Gas - liquid separator

10

ejector

11

liquid separator

12

Expansion valve defrost / cooling

13

check valve

14

check valve

15

check valve

16

Four-way switching valve

17

Low pressure section pressure sensor

18

Low pressure section temperature sensor

19

Pressure sensor high pressure section

20

High-pressure section temperature sensor

21

leader

22

return

23

consumer cycle

24

check valve

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 0866291 B1 [0004]

Claims (19)

Compression heat pump or compression refrigeration machine with a refrigerant circuit that contains an evaporator (5), a compressor (6), a condenser (1) and a controllable expansion valve (4), which is controlled by a control device, with a first pressure sensor (19) for detection a pressure P2 is provided in a high pressure or hot gas portion of the refrigerant circuit; characterized in that: a second pressure sensor (17) is provided for detecting a pressure P1 in a low-pressure or suction gas section of the refrigerant circuit. compression heat pump or compression chiller claim 1 , characterized in that the second pressure sensor (17) is arranged between the evaporator (5) and the compressor (6). compression heat pump or compression chiller claim 1 or 2 , characterized in that a temperature sensor (18) is provided for detecting a temperature T2 in the low-pressure or suction gas section of the refrigerant circuit. compression heat pump or compression chiller claim 3 , characterized in that the temperature sensor (18) is arranged between the evaporator (5) and the compressor (6). Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that the first pressure sensor (19) is arranged between the condenser (1) and the expansion valve (4), preferably between the condenser and a subcooler (3). Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that the first pressure sensor (19) is arranged on a refrigerant collector (2). Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that a further temperature sensor (20) is provided for detecting a temperature T1 in the high-pressure or hot gas section of the refrigerant circuit, which is preferably arranged between the compressor (6) and the condenser (1). . Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that the first pressure sensor (19) is arranged on a refrigerant collector (2). Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that an overheating heat exchanger (9) is provided between the condenser (1) or a subcooler (3) arranged downstream of the condenser (1) and the expansion valve (4) for heat exchange between the Evaporator (5) flowing towards and from this to the compressor (6) flowing away refrigerant. Compression heat pump or compression refrigeration machine according to one of the preceding claims, characterized in that the compression heat pump is an air heat pump which extracts heat from the ambient air and supplies it to a consumer. Method for operating a compression heat pump or a compression refrigeration machine according to one of the preceding claims, characterized in that iv. Depending on the heat source temperature or the evaporation temperature and the required flow temperature or the condensation temperature, a target value for optimized hot gas overheating is set, v. the instantaneous hot-gas superheat from the difference between a temperature determined from the pressure (P2) or a measured temperature (T1) in the high-pressure or hot-gas section of the refrigerant circuit and a temperature determined from the pressure (P1) or a measured temperature (T2) in the low-pressure section or suction gas section of the refrigerant circuit is determined, vi. the expansion valve (4) is controlled in such a way that the hot gas superheat approaches the target value. procedure after claim 11 , characterized in that iii. if the hot gas overheating is too low compared to the target value, the expansion valve (4) is closed further, iv. the expansion valve (4) is opened further if the hot gas overheating is too high compared to the target value. procedure after claim 11 or 12 , characterized in that the target value represents the value of an optimized efficiency of the compression heat pump. procedure after Claim 13 , characterized in that for different heat source temperatures and / or different flow temperatures respectively fixed target values are stored in tabular form in a control device of the compression heat pump. procedure after Claim 14 , characterized in that target values for different heat source temperatures and/or different flow temperatures are determined before being stored in tabular form from measurements of the efficiency of the heat pump as a function of the hot gas overheating at the different heat source temperatures. procedure after claim 15 , characterized in that a target value for a heat source temperature is determined from efficiency measurements in which the hot gas superheat is measured in increments of 5k to 15K over a range from a minimum hot gas superheat of 10K to 30K to a maximum hot gas superheat of 35K to 80K, and the hot gas overheating with maximum efficiency is stored as the target value for this heat source temperature. Method according to any of the preceding Claims 11 until 16 , characterized in that as a heat source temperature approximately determined from the pressure (P1) or the measured temperature (T2) is used in the low-pressure or suction gas section of the refrigerant circuit. Method according to any of the preceding Claims 11 until 17 , characterized in that for a heat source temperature in a range from -10°C to -5°C a target value for the hot gas overheating in a range from 32K to 42K, preferably from 35K to 40K is fixed. Method according to any of the preceding Claims 11 until 18 , characterized in that for a heat source temperature in a range from - 5°C to +5°C a target value for the hot gas overheating in a range from 17K to 27K, preferably from 19K to 25K is specified.

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