Heat pump refrigeration circuit and heat pump

Abstract

The present invention relates to a refrigeration circuit (200) of a heat pump (100), in particular an air-to-water heat pump, a brine-to-water heat pump, an air-to-air heat pump, or a water-to-water heat pump, wherein the refrigeration circuit (200) comprises a compressor (210), a first heat exchanger (220), a second heat exchanger (240), a throttle device (230, 235), and a refrigerant collector (260), wherein the throttle device (230, 235) comprises two expansion valves (230, 235) arranged on either side of the refrigerant collector (260) in the refrigeration circuit (200). The invention also relates to an associated heat pump (100).

Description

[0001] The present invention relates to a refrigeration circuit of a heat pump and an associated heat pump system.

[0002] Heat pump refrigeration circuits are well known. The current state of the art is refrigeration circuits consisting of a compressor, evaporator, condenser, and expansion valve. Refrigeration circuits with additional components are known, but they require high costs for little efficiency benefit. For example, various additions have been implemented for different refrigerants, such as intermediate refrigerant injection for R410A and a recuperator for R454C.

[0003] EP 2 664 868 B1 discloses a heat pump device comprising a compressor, a condenser, a first heat exchanger, an electronic expansion valve, and a four-way / two-way valve arranged in a refrigeration circuit. The first heat exchanger has a first refrigerant line for absorbing heat through evaporation of the refrigerant and a second refrigerant line for releasing heat through subcooling of the liquid refrigerant. Furthermore, it has a plurality of fins and a defrosting tray. At least one of the fins has an extension at its ends, which serves to accommodate the second line, which is part of the refrigeration circuit and is configured as a defrosting coil, in which liquid refrigerant flows and is used to heat the defrosting tray.

[0004] The object of the invention is to improve the efficiency of the refrigeration circuit. A further object is to keep the complexity and cost of the refrigeration circuit as low as possible. In particular, a further object of the invention is to achieve optimal use of environmental energy by using a flammable refrigerant such as R290.

[0005] According to the invention, the object is achieved with the refrigeration circuit according to claim 1. Preferred embodiments are defined in the dependent claims.

[0006] In one aspect, a refrigeration circuit of a heat pump is proposed, in particular an air-water heat pump, a brine-water heat pump, an air-air heat pump or a water-water heat pump, wherein the refrigeration circuit has a compressor, a condenser, an evaporator, a throttle device and a refrigerant collector.

[0007] The throttling device has two expansion valves arranged on either side of the refrigerant collector in the refrigeration circuit.

[0008] The expansion valves located on either side of the refrigerant receiver allow an intermediate pressure between high and low pressure to develop in the refrigerant receiver area. The two expansion valves thus enable advantageous independent control of subcooling and superheating. The use of the second expansion valve thus achieves controlled subcooling at low cost.

[0009] Preferably, subcooling will be generated by a second expansion valve and an increase in efficiency will be achieved.

[0010] The refrigerant collector is preferably designed for refrigerant flow through it on both sides.

[0011] This makes it possible to dispense with bypass lines and similar devices for bridging the collector in reverse operation.

[0012] The refrigerant collector has the following features so that it is designed for flow on both sides.

[0013] The refrigerant collector is advantageously designed to be directionally symmetrical with regard to "flow guidance", i.e. the respective inflow and outflow pipes are arranged in a similar geometrical manner, in contrast to a "unidirectional" collector.

[0014] The respective inlet and outlet pipes are advantageously designed to extract the refrigerant at the bottom of the receiver. Their open ends are therefore advantageously arranged at a similar height.

[0015] The respective inlet / outlet pipes are arranged in such a way that the pipe ends in the collector vessel are positioned as close to the ground as possible in every flow direction in order to immerse themselves in liquid refrigerant even when the collector fill level is low.

[0016] Preferably, a partially refrigerant-permeable flow-calming device, such as a separating plate, is installed in the lower part of the collector between the respective inlet pipe / outlet pipe.

[0017] Preferably, the refrigeration circuit has a 4 / 2-way valve and is designed for circuit reversal.

[0018] Such a refrigeration circuit is particularly advantageous for air-to-water heat pumps or air-to-air heat pumps, since the circuit reversal can be used to defrost a frozen heat exchanger.

[0019] Preferably, the refrigeration circuit comprises a flammable refrigerant, in particular comprising or consisting of R290.

[0020] Preferably, the expansion valves comprise a first expansion valve and a second expansion valve, and the first expansion valve is controllable independently of the second expansion valve.

[0021] Independent control means that a heat pump control can control one of the two expansion valves without automatically influencing the other expansion valve.

[0022] Preferably, the first expansion valve is designed for subcooling control and the second expansion valve is designed for superheating control.

[0023] The first expansion valve is preferably located upstream of the refrigerant receiver in the direction of refrigerant flow, and the second expansion valve is preferably located downstream of the refrigerant receiver in the direction of refrigerant flow. If the flow direction is reversed, the assignment of the two expansion valves changes accordingly.

[0024] The subcooling control regulates the degree of opening of the first expansion valve in the direction of refrigerant flow on the basis of a subcooling setpoint (UK setpoint) determined for the optimum efficiency of the refrigeration circuit at the respective operating point and an actual subcooling value (UK actual value) determined on the basis of the condensation temperature of the refrigerant in the condensing heat exchanger and the refrigerant outlet temperature from the condensing heat exchanger in such a way that the control deviation between the UK setpoint and the UK actual value is zero. If the UK actual value is too small, the first expansion valve is closed further and if the UK actual value is too large, the valve is opened further.

[0025] The UK setpoint can, for example, be stored in a table for different condensation temperatures or determined using a model, without being limited to these methods.

[0026] The superheat control regulates the degree of opening of the second expansion valve in the direction of refrigerant flow on the basis of a superheat setpoint (ÜB setpoint) determined for safe operation and optimum efficiency of the refrigeration circuit at the respective operating point and an actual superheat value (ÜB actual value) determined on the basis of the evaporation temperature of the refrigerant in the evaporating heat exchanger and the refrigerant outlet temperature from the evaporating heat exchanger in such a way that the control deviation between the ÜB setpoint and the ÜB actual value is zero. If the ÜB actual value is too small, the second expansion valve is closed further and if the ÜB actual value is too large, the second expansion valve is opened further.

[0027] Preferably, the refrigeration circuit further comprises a defrost coil. The defrost coil is particularly suitable for defrosting a condensate tray when necessary using heat from the refrigerant, in particular condensed refrigerant, and thus keeps the condensate tray ice-free.

[0028] The evaporating heat exchanger is advantageously defrosted by reversing the circuit.

[0029] Preferably, the defrost coil is located between one of the expansion valves and the refrigerant receiver in the refrigeration circuit. The temperature level of the refrigerant at the intermediate pressure level is particularly energy-efficient for thawing the frozen condensate pan.

[0030] During normal operation, the defrost coil is preferably arranged directly before or after the refrigerant receiver.

[0031] Preferably, the refrigeration circuit further comprises a check valve and / or a filter dryer.

[0032] In a further aspect, a heat pump, in particular an air-water heat pump, brine-water heat pump, air-air heat pump or water-water heat pump, with a refrigeration circuit according to the invention is proposed.

[0033] Preferably, the heat pump further comprises a controller, wherein the controller is designed to implement subcooling control by means of the first of the two expansion valves and superheating control by means of the second of the two expansion valves.

[0034] According to one aspect of the invention, the first expansion valve (230) is designed for subcooling control in heating mode and the second expansion valve (235) is designed for superheating control.

[0035] In reverse operation, i.e. in cooling mode or defrosting mode, the situation is the other way around, since the flow direction of the refrigerant is first directed through the second expansion valve (235), which is then designed to control subcooling, and then through the first expansion valve (230), which is then designed to control superheating.

[0036] Preferably, the control is designed to reverse the refrigerant circuit through the refrigerant collector.

[0037] The reversal of the refrigerant circuit is advantageously carried out by the 4 / 2 way valve.

[0038] Further advantages and preferred embodiments are described below with reference to the attached figures.

[0039] Here we show: Fig. 1 schematically and exemplarily a first refrigeration circuit; Fig. 2 schematically and exemplarily a second refrigeration circuit; Fig. 3 schematically and exemplarily a third refrigeration circuit Fig. 4 schematically and exemplarily a fourth refrigeration circuit Fig. 5 schematically and exemplarily a fifth refrigeration circuit

[0040] Fig. 1 shows schematically and exemplarily a heat pump 100 with a vapor compression system or refrigeration circuit 200. In Fig. 1 The heat pump 100 is designed as a water / water heat pump or as a brine / water heat pump, so that a circuit reversal is not necessary, but is optionally possible, for example via additional switching valves.

[0041] In the refrigeration circuit 200, a compressor 210, an optional check valve 215, a first heat exchanger 220, a first throttle element 230, a second throttle element 235, a second heat exchanger 240, a refrigerant receiver 260 and an optional filter dryer 265 are shown.

[0042] In the compressor 210, the refrigerant is increased in pressure, or compressed, to high pressure (HD). The refrigerant compressed to the high pressure (HD) then flows, in heating mode, through the optional check valve 215 downstream of the compressor 210 and to the first heat exchanger 220.

[0043] The first heat exchanger 220 is operated as a condensing heat exchanger in heating mode and is designed as a condenser in which the refrigerant can be condensed and preferably subcooled. The first heat exchanger 220 is connected to a heat sink system 400, in which, in particular, a heating medium is circulated in a heating medium flow direction.

[0044] In the heating mode shown, the first throttle element 230 is configured as an intermediate pressure throttle element, in which the refrigerant is expanded from a high pressure (HD) to an intermediate pressure (ZD). This intermediate pressure is also referred to as the intermediate pressure (MD).

[0045] The second heat exchanger 240 is operated as an evaporating heat exchanger in heating mode and is designed as an evaporator in which the refrigerant is evaporated.

[0046] A temperature sensor (not shown) is provided in the exemplary embodiment and is suitable for measuring the temperature of the refrigerant at a high pressure (HD) during cooling operation as it exits the heat exchanger condensing during cooling operation and transmitting the temperature to the controller. The controller is suitable for using the temperature sensor during cooling operation to measure the temperature of the refrigerant at a high pressure (HD).

[0047] In addition to these components or parts of the vapor compression system 200, a heat source system 300 is provided. The heat source system 300 serves to exchange heat of a source medium with the refrigerant, whereby energy of the heat source system 300 is exchanged with the vapor compression system 200. In the example of the Fig. 1 The heat source system 300 is a system with water or brine as the source medium.

[0048] The heat sink system 400 can, in particular, be a hot water system via an apartment station, a hot water tank, or even a conventional building heating system. In the first heat exchanger 220, the temperature of the refrigerant is significantly reduced. The first heat exchanger 220 used here is designed as a condensing heat exchanger such that it can accommodate liquefied refrigerant, which can also be further subcooled in the first heat exchanger 220, i.e., brought to temperatures below the condensation temperature. Thus, the first heat exchanger 220 is suitable for accommodating liquid refrigerant at different levels or different masses or volumes of liquid refrigerant.

[0049] In heating mode, the liquefied and preferably subcooled refrigerant flows from the first heat exchanger 220 to the first throttle element 230. With the first throttle element 230, which is operated as an intermediate pressure throttle element in heating mode, the refrigerant is expanded to the intermediate pressure ZD.

[0050] The refrigerant at the intermediate pressure ZD continues to flow after the first throttle element 230 to the refrigerant collector 260. Refrigerant that is not required for the operation of the refrigeration circuit, in particular at the respective operating point, collects or remains in the refrigerant collector 260, preferably with a liquid phase and an associated volume or mass and / or a partially gaseous phase above the liquid phase.

[0051] The refrigerant, still at the intermediate pressure ZD, now flows into the second throttle element 235, which operates as a low-pressure throttle element in heating mode. In the second throttle element 235, the refrigerant is expanded to the low pressure ND in heating mode, continues to flow in a low-pressure flow direction into the second heat exchanger 240, which operates as an evaporating heat exchanger in heating mode, absorbs energy, and evaporates—a cycle in the vapor compression system 200 is closed.

[0052] The refrigerant collector 260 advantageously accommodates a mass of liquid refrigerant, which in particular should not remain in the condensing heat exchanger. Furthermore, active refrigerant, which participates in particular in thermal processes in the vapor compression system, is located in the evaporating heat exchanger, the compressor, and any internal heat exchanger provided. The refrigerant collector 260 thus serves as a buffer storage for refrigerant not required for the thermal processes.

[0053] Fig. 2 shows schematically and exemplarily another refrigeration circuit 200 of a heat pump 100.

[0054] The refrigeration circuit 200 of the Fig. 2 differs from the refrigeration circuit of the Fig. 1 in that the heat source system 300 provides air as the heat source and, accordingly, a fan 310 is provided that conveys air through the heat exchanger 240. An injection capillary 247 is also provided for the heat exchanger 240, which in this embodiment is configured as an air / refrigerant heat exchanger. Furthermore, a switching valve 270 is provided, with which the flow direction of the refrigeration circuit 200 can be reversed.

[0055] In heating mode, energy is transferred from the source medium to the refrigerant in the second heat exchanger 240, thus evaporating the refrigerant in the second heat exchanger 240, which operates as an evaporating heat exchanger in heating mode. The controller treats the first heat exchanger 220 as a condensing heat exchanger in heating mode.

[0056] In cooling mode, i.e. when the changeover valve 270 is in the Fig. 2 In a different position (not shown), energy is transferred from the refrigerant to the source medium, thus condensing the refrigerant in the second heat exchanger 240, which operates as a condensing heat exchanger in the cooling mode. The controller treats the second heat exchanger 240 as a condensing heat exchanger in the cooling mode.

[0057] If the changeover valve 270 is in the operating position "Heating" - heating mode - as shown in Figur 2 As shown, the refrigeration circuit 200 absorbs source energy from the heat source system 300. The refrigerant evaporates in the second heat exchanger 240 before the refrigerant flows into the compressor 210 or is sucked in by it.

[0058] Fig. 3 shows schematically and exemplarily a third refrigeration circuit 200. The refrigeration circuit of the Fig. 3 differs from the refrigeration circuit 200 of the Fig. 2 in which the first heat exchanger 220 is also designed as a refrigerant / air heat exchanger. The heat pump 100 of the Fig. 3 is therefore an air-to-air heat pump. Therefore, a fan 410 is also provided in the vicinity of the first heat exchanger 220.

[0059] Fig. 4 shows schematically and exemplarily a fourth refrigeration circuit 200. The refrigeration circuit 200 of the Fig. 4 In addition to the cooling circuit, the Fig. 2 a defrost coil 290 which is arranged between the first throttle element 230 and the refrigerant collector 260.

[0060] The defrost coil 290 is in particular a part of the refrigeration circuit in which liquid refrigerant flows and which is designed to heat a defrost pan of the second heat exchanger 240.

[0061] Fig. 5 shows schematically and exemplarily a fifth refrigeration circuit 200. The refrigeration circuit 200 differs from the refrigeration circuit of the Fig. 4in the position of the defrost coil 290, which in this embodiment is arranged between the refrigerant collector 260 and the second throttle element 235.

Claims

1. Refrigeration circuit (200) of a heat pump (100), in particular an air-water heat pump, a brine-water heat pump, an air-air heat pump or a water-water heat pump, wherein the refrigeration circuit (200) comprises a compressor (210), a first heat exchanger (220), a second heat exchanger (240), a throttle device (230, 235) and a refrigerant collector (260), characterized in that the throttle device (230, 235) has two expansion valves (230, 235) which are arranged on both sides of the refrigerant collector (260) in the refrigeration circuit (200).

2. Refrigeration circuit (200) according to claim 1, wherein the refrigerant collector (260) is designed for refrigerant to flow through on both sides.

3. Refrigeration circuit (200) according to claim 1 or 2, wherein the refrigeration circuit (200) has a 4 / 2-way valve (270) and is designed for circuit reversal.

4. Refrigeration circuit (200) according to one of the preceding claims, wherein the refrigeration circuit (200) comprises a flammable refrigerant, in particular comprising or consisting of R290.

5. Refrigeration circuit (200) according to one of the preceding claims, wherein the expansion valves (230, 235) comprise a first expansion valve (230) and a second expansion valve (235), and the first expansion valve (230) is controllable independently of the second expansion valve (235).

6. Refrigeration circuit (200) according to claim 5, wherein the first expansion valve (230) is designed for subcooling control and the second expansion valve (235) is designed for superheating control.

7. Refrigeration circuit (200) according to one of the preceding claims, further comprising a defrost coil (290).

8. Refrigeration circuit (200) according to claim 7, wherein the defrost coil (290) is arranged between one of the expansion valves (230, 235) and the refrigerant collector (260) in the refrigeration circuit (200).

9. Refrigeration circuit (200) according to claim 8, wherein the defrost coil (290) is arranged directly before or after the refrigerant collector (260) in normal operation.

10. Refrigeration circuit (200) according to one of the preceding claims, further comprising a check valve (210) and / or a filter dryer (265).

11. Heat pump (100), in particular air-water heat pump, brine-water heat pump, air-air heat pump or water-water heat pump, with a refrigeration circuit (200) according to one of the preceding claims.

12. Heat pump (100) according to claim 11, further comprising a controller, wherein the controller is configured to implement subcooling control by means of the first of the two expansion valves (230, 235) and superheating control by means of the second of the two expansion valves (230, 235).

13. Heat pump (100) according to claim 12, wherein the control is designed to reverse the refrigerant circuit (200) through the refrigerant collector (260).

14. Heat pump (100) according to claim 12 or 13, wherein the control for reversing the refrigerant circuit (200) is carried out by the 4 / 2-way valve, wherein the refrigerant collector (260) is suitable for flow in two directions.

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