Heat pump device

Abstract

A heat pump device (1) is provided with a refrigerant circulation path (F1) in which a refrigerant flows and in which the following are connected in an annular manner: a compressor (11), a first heat exchanger (13), a first expansion valve (14), a second heat exchanger (15), a second expansion valve (16), and a third heat exchanger (17). The heat pump device (1) is further provided with a first injection flow path (F2) that returns a portion of the refrigerant cooled by the first heat exchanger (13) to the intake side of a second compression mechanism (11H) via a third expansion valve (19) and the second heat exchanger (15). The heat pump device (1) is further provided with a control device (100) configured to observe the state of the refrigerant circulation path (F1) and control the degree of opening of the third expansion valve (19) in accordance with the observation results.

Description

heat pump equipment

[0001] The present disclosure relates to a heat pump device.

[0002] As regulations regarding the performance of refrigeration and air conditioning equipment become stricter in various countries, there is a demand for heat pump designs that enable more efficient operation.

[0003] Many developments have been made to date with the aim of improving the efficiency of heat pumps. One method of reducing losses in heat pumps is the introduction of intermediate pressure injection. Japanese Patent Laid-Open Publication No. 2007-278686 (Patent Document 1) discloses a heat pump water heater that incorporates intermediate pressure injection.

[0004] Japanese Patent Application Laid-Open No. 2007-278686

[0005] Heat pump devices using intermediate pressure injection have been developed to date, as shown in Japanese Patent Laid-Open No. 2007-278686 (Patent Document 1). However, there has been little development focused on reducing exergy loss. It is known that reducing exergy loss improves the performance of heat pumps, and development focused on reducing exergy loss will enable the design of more efficient heat pumps.

[0006] An object of the present disclosure is to provide a heat pump device that can reduce exergy loss and further improve the efficiency of the heat pump.

[0007] The present disclosure relates to a heat pump apparatus that exchanges heat with a user-side device. The heat pump apparatus includes a refrigerant circulation path in which a refrigerant flows, including a compressor, a first heat exchanger, a first expansion valve, a second heat exchanger, a second expansion valve, and a third heat exchanger connected in a ring shape. The first heat exchanger is configured to exchange heat between the refrigerant and outside air. The second heat exchanger is configured to exchange heat between refrigerants. The third heat exchanger is configured to exchange heat between the refrigerant and a liquid medium used in the user-side device. The compressor includes a first compression mechanism that compresses the refrigerant heated by the third heat exchanger and a second compression mechanism that further compresses the refrigerant pressurized by the first compression mechanism. The heat pump apparatus further includes a first injection flow path including a third expansion valve. The first injection flow path returns a portion of the refrigerant cooled by the first heat exchanger to the suction side of the second compression mechanism via the third expansion valve and the second heat exchanger. The second heat exchanger is configured to exchange heat between the refrigerant cooled by the first heat exchanger and the refrigerant decompressed by the third expansion valve. The heat pump device further includes a control device configured to monitor the state of the refrigerant circulation path and control the opening degree of the third expansion valve in accordance with the monitoring result.

[0008] According to the heat pump device of the present disclosure, by focusing on the exergy loss associated with superheating of the refrigerant discharged from the compressor and controlling the expansion valve in the injection flow path using a map that outputs a control target value that reduces the loss, it is possible to operate at a more efficient operating point.

[0009] 1 is a refrigerant circuit diagram of a heat pump device according to a first embodiment. FIG. 2 is a diagram for explaining exergy loss in an ideal single-stage refrigeration cycle. FIG. 3 is a diagram for explaining exergy loss in a refrigeration cycle when intermediate pressure injection is installed. FIG. 4 is a control flowchart of an injection expansion valve according to the first embodiment. FIG. 5 is a diagram showing a target value map (f=100 Hz) of discharge SH according to the first embodiment. FIG. 6 is a diagram showing a target value map (f=80 Hz) of discharge SH according to the first embodiment. FIG. 7 is a control flowchart of an injection expansion valve using an outside air temperature, an average inlet and outlet water temperature, and a compressor frequency according to a first modified example of the first embodiment. FIG. 8 is a diagram showing a target value map (cooling operation, f=100 Hz) of discharge SH using an outside air temperature, an average inlet and outlet water temperature, and a compressor frequency according to a first modified example of the first embodiment. FIG. 9 is a diagram showing a target value map (cooling operation, f=80 Hz) of discharge SH using an outside air temperature, an average inlet and outlet water temperature, and a compressor frequency according to a first modified example of the first embodiment. 1 is a diagram showing a target value map (heating operation, f=100 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the compressor frequency according to a first modification of the first embodiment. FIG. 2 is a diagram showing a target value map (heating operation, f=80 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the compressor frequency according to a first modification of the first embodiment. FIG. 3 is a control flowchart of an injection expansion valve using the outside air temperature, the average inlet and outlet water temperature, and the product of the inlet and outlet water temperature difference and the water flow rate according to a second modification of the first embodiment. FIG. 4 is a diagram showing a target value map (cooling operation, f=100 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the product of the inlet and outlet water temperature difference and the water flow rate according to a second modification of the first embodiment. FIG. 5 is a diagram showing a target value map (cooling operation, f=80 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the product of the inlet and outlet water temperature difference and the water flow rate according to a second modification of the first embodiment. Fig. 10 is a diagram showing a target value map (heating operation, f=100 Hz) of discharge SH using the outside air temperature and the inlet / outlet average water temperature, and the product of the inlet / outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1. Fig. 11 is a diagram showing a target value map (heating operation, f=80 Hz) of discharge SH using the outside air temperature and the inlet / outlet average water temperature, and the product of the inlet / outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1. Fig. 12 is a refrigerant circuit diagram of a heat pump device according to Embodiment 2.Fig. 10 is a control flowchart of an injection expansion valve according to embodiment 2. Fig. 11 is a diagram showing a target value map (f=100 Hz) of the intermediate pressure PM used in embodiment 2. Fig. 12 is a diagram showing a target value map (f=80 Hz) of the intermediate pressure PM used in embodiment 2. Fig. 13 is a refrigerant circuit diagram of a heat pump device according to embodiment 3.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Below, embodiments including multiple modifications will be described, but it was originally intended that the configurations described in each embodiment be combined as appropriate. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0011] Embodiment 1. Fig. 1 is a refrigerant circuit diagram of a heat pump device according to embodiment 1. Note that Fig. 1 functionally illustrates the connection relationships and arrangement of each device in the heat pump device, and does not necessarily illustrate the physical spatial arrangement.

[0012] Referring to Figure 1, the heat pump device 1 includes a compressor 11, a first heat exchanger 13, a fan 13F, a first expansion valve 14, a second heat exchanger 15, a second expansion valve 16, a third heat exchanger 17, a four-way valve 12, an accumulator 18, and piping 80 to 88.

[0013] The first heat exchanger 13 is configured to exchange heat between the refrigerant and outside air. The second heat exchanger 15 has a first passage H1 and a second passage H2 and is configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2. The third heat exchanger 17 is configured to exchange heat between the refrigerant and a liquid medium (e.g., water, brine, etc.) used in a user-side device (hot water supply, heating / cooling, etc.).

[0014] The compressor 11 has a suction port G1, a discharge port G2, and an intermediate-pressure port G3. The compressor 11 includes a low-stage compression mechanism 11L that compresses the refrigerant drawn through the suction port G1, and a high-stage compression mechanism 11H that further compresses the refrigerant pressurized by the compression mechanism 11L.

[0015] The compressor 11 compresses the refrigerant drawn from the pipe 88 and discharges it to the pipe 80. The compressor 11 can arbitrarily change the drive frequency of the motor that drives the compression mechanism through inverter control. The compressor 11 is also provided with an intermediate pressure port G3, allowing refrigerant from the intermediate pressure port G3 to flow into the middle of the compression process. The compressor 11 is configured to change the operating frequency f of the built-in motor in accordance with a control signal from the control device 100, thereby adjusting the rotation speed of the compression mechanisms 11L and 11H. Adjusting the rotation speed of the compression mechanisms 11L and 11H adjusts the amount of refrigerant circulating, thereby adjusting the capacity of the heat pump device 1. Various types of compression mechanisms 11L and 11H can be used for each of the compression mechanisms 11L and 11H, such as a scroll type, rotary type, or screw type.

[0016] The heat pump device 1 includes a refrigerant circulation path F1 and an injection path F2 as paths through which the refrigerant flows.

[0017] When the four-way valve 12 is set as shown by the solid lines in Figure 1 (for example, during air conditioning operation or cooling operation), in the refrigerant circulation path F1, the refrigerant flows from the discharge port G2 of the compressor 11, passes through the first heat exchanger 13, the first expansion valve 14, the passage H1 of the second heat exchanger 15, the second expansion valve 16, and the third heat exchanger 17 in that order, and then flows via the accumulator 18 to return to the suction port G1 of the compressor 11.

[0018] The heat pump device 1 further includes pipes 91-93 that form an injection flow path F2, and a third expansion valve 19. The third expansion valve 19 is disposed on the injection flow path F2 at a position between a branch point where the injection flow path F2 branches off from the refrigerant circulation path F1 and a passage H2 of the second heat exchanger 15. The injection flow path F2 bypasses the refrigerant from a position between the first expansion valve 14 and the second heat exchanger 15 to the suction side of the compression mechanism 11H of the compressor 11. In the injection flow path F2, the refrigerant branched from the refrigerant circulation path F1 passes through the pipe 91, the third expansion valve 19, the pipe 92, the passage H2 of the second heat exchanger 15, and the pipe 93 in that order, and flows to the intermediate pressure port G3 of the compressor 11.

[0019] The first heat exchanger 13 is configured so that the high-temperature, high-pressure gas refrigerant discharged from the compressor 11 exchanges heat (radiates heat) with outside air. This heat exchange causes the refrigerant to condense and change into a liquid phase. The refrigerant discharged from the compressor 11 to the pipe 80 passes through the four-way valve 12 and the pipe 81, then condenses and liquefies in the first heat exchanger 13 and flows out into the pipe 82. A fan 13F that blows outside air is attached to the first heat exchanger 13 to increase the efficiency of the heat exchange. The fan 13F supplies the outside air to the first heat exchanger 13, with which the refrigerant exchanges heat in the first heat exchanger 13. The refrigerant pressure on the discharge side of the compressor 11 (high-pressure side pressure PH) can be adjusted by adjusting the rotation speed of the fan 13F.

[0020] The heat pump device 1 further includes pressure sensors 110, 111, temperature sensors 120-123, a flow rate sensor 124, and a control device 100 that controls the compressor 11, the first expansion valve 14, the second expansion valve 16 and the third expansion valve 19.

[0021] The pressure sensor 110 detects the pressure PL at the suction port of the compressor 11 and outputs the detected value to the control device 100. The pressure sensor 111 detects the discharge pressure PH of the compressor 11 and outputs the detected value to the control device 100.

[0022] The temperature sensor 120 detects the discharge temperature TH of the compressor 11 and outputs the detected value to the control device 100. The temperature sensor 121 detects the liquid medium inlet temperature Tw1 of the third heat exchanger 17 and outputs the detected value to the control device 100. The temperature sensor 122 detects the liquid medium outlet temperature Tw2 of the third heat exchanger 17 and outputs the detected value to the control device 100. The temperature sensor 123 detects the outside air temperature Ta and outputs the detected value to the control device 100.

[0023] The flow rate sensor 124 detects the flow rate of the liquid medium in the third heat exchanger 17 and outputs the detected value to the control device 100 .

[0024] In this embodiment, the injection flow path F2 controls the discharge temperature TH of the compressor 11 by causing the decompressed two-phase refrigerant to flow into the compressor 11.

[0025] The control device 100 is configured to include a CPU (Central Processing Unit) 102, memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input / output buffer (not shown) for inputting and outputting various signals, etc. The CPU 102 deploys a program stored in the ROM into the RAM, etc., and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 100 are written. The control device 100 controls each device in the heat pump device 1 in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

[0026] In the heat pump device 1, a compressor 11, a four-way valve 12, a first heat exchanger 13, a first expansion valve 14, a second heat exchanger 15, a second expansion valve 16, a third heat exchanger 17, and an accumulator 18 are connected in a ring shape in this order, and a refrigeration cycle is formed by circulating the refrigerant through the refrigerant circulation path F1.

[0027] In cooling operation, the control device 100 sets the internal flow path of the four-way valve 12 as shown by the solid lines, fully opens the first expansion valve 14, and controls the refrigeration cycle using the second expansion valve 14. In heating operation or hot water supply operation, the control device 100 sets the internal flow path of the four-way valve 12 as shown by the dashed lines, fully opens the second expansion valve 16, and controls the refrigeration cycle using the first expansion valve 14.

[0028] Next, how the exergy loss is reduced in this embodiment will be described. Fig. 2 is a diagram for explaining the exergy loss in an ideal single-stage refrigeration cycle. Fig. 3 is a diagram for explaining the exergy loss in a refrigeration cycle equipped with intermediate pressure injection.

[0029] As shown in FIG. 2, in the single-stage cycle shown by points 1 → 2 → 3 → 4 → 5 → 1, the exergy loss L due to superheating of the compressor discharge refrigerant is much lower than in the ideal Carnot cycle shown by points 1 → 8 → 4 → 6 → 1. Ｃ and the exergy loss L due to the pressure loss when passing through the expansion valve. ＸOn the other hand, as shown in Figure 3, when intermediate pressure injection is installed, the exergy loss due to the superheating of the refrigerant discharged from the compressor is Ｃ，Ｈ and loss L Ｃ，Ｌ This is the sum of the loss L in FIG. Ｃ Similarly, the exergy loss due to the pressure loss when passing through the expansion valve is smaller than the loss L Ｘ，Ｈ and loss L Ｘ，Ｌ This is the sum of the loss L in FIG. Ｘ Therefore, by performing intermediate pressure injection, it is possible to temporarily reduce the entropy at the intermediate pressure, thereby reducing the exergy loss.

[0030] Fig. 4 is a control flowchart of the injection expansion valve according to embodiment 1. Hereinafter, the operation shown in the control flowchart of Fig. 4 will be referred to as the reference operation.

[0031] First, in the standard operation, in step ST1, the control device 100 determines whether the discharge temperature TH is equal to or lower than a predetermined upper limit temperature. The upper limit temperature is set, for example, to protect the motor windings of the compressor 11 from high temperatures. If the discharge temperature TH is equal to or lower than the upper limit temperature (YES in ST1), the control device 100 executes the process of step ST3. If the discharge temperature TH is higher than the upper limit temperature (NO in ST1), the control device 100 executes the process of step ST2.

[0032] In step ST2, the control device 100 increases the opening of the third expansion valve 19 (shown as INJ-LEV in FIG. 4) in the injection flow path F2 so that the discharge temperature TH becomes lower than the upper limit temperature. This reduces the discharge temperature TH, making it possible to protect the motor windings from high temperatures.

[0033] On the other hand, if the process proceeds to step ST3, the control device 100 determines whether the heating degree of the refrigerant discharged from the compressor 11 (hereinafter referred to as "discharge SH") is equal to or greater than a lower limit. The discharge SH is calculated as the difference (=TH-CT) between the temperature TH detected by the temperature sensor 120 and the saturation temperature CT corresponding to the discharge pressure PH detected by the pressure sensor 111.

[0034] If the discharge SH is lower than the lower limit (NO in ST3), there is a risk that the discharged refrigerant will be in a two-phase state, so in step ST4, the control device 100 fully closes the third expansion valve 19 and ends the processing of the flowchart in Fig. 4. When the third expansion valve 19 is fully closed, the discharge SH increases.

[0035] On the other hand, if the discharge SH is equal to or greater than the lower limit (YES in ST3), the control device 100 executes the process of step ST5. In step ST5, the control device 100 obtains a target value for the discharge SH from a map. The map used here takes three variables, namely, the condensing temperature (hereinafter referred to as CT), the evaporating temperature (hereinafter referred to as ET), and the compressor frequency f, as input, and pre-stores the corresponding discharge SH values ​​that reduce exergy loss and maximize operating efficiency. The target value for the discharge SH that reduces exergy loss and maximizes operating efficiency can be determined in advance by experiment, simulation, or the like.

[0036] Subsequently, in step ST6, the control device 100 controls the opening degree of the third expansion valve 19 so that the discharge SH is equal to the target value acquired in step ST5.

[0037] Here, we will explain CT and ET used as input values ​​of the map in step ST5 of Fig. 4. The control device 100 obtains CT from a map that stores in advance the relationship between the discharge pressure PH of the compressor 11 and the saturation temperature (=CT) corresponding to the discharge pressure PH of the compressor 11. The control device 100 also obtains ET from a map that stores in advance the relationship between the suction pressure PL and the saturation temperature (=ET) corresponding to the suction pressure PL.

[0038] The target values ​​in the maps of FIGS. 5 and 6 are set to values ​​calculated in advance by simulation under the conditions of desired CT, ET, and compressor frequency f.

[0039] Each target value stored as a map is determined in advance by simulation. For example, the target value SH １－１ For this, a parameter study was carried out with ET = -10 (°C) and CT = 30 (°C), and the optimum discharge SH that minimizes the loss was obtained by simulation, and the target value SH １－１ Let's say.

[0040] Fig. 5 is a diagram showing a target value map (f=100 Hz) of the discharge SH according to embodiment 1. Fig. 6 is a diagram showing a target value map (f=80 Hz) of the discharge SH according to embodiment 1.

[0041] Here, the map number is represented by N, and the map numbers in Figs. 5 and 6 are N=1 and N=2, respectively. ｍｉｎ is the minimum value of the heating degree (a positive value close to 0), and "←" is SH ｍｉｎ and other target values ​​are SH Ｎ－Ｍ Let's say. SH Ｎ－Ｍ In the above formula, N indicates the map number, and M indicates the number of the target value in each map. In each map, the magnitude relationship of the target value has the following relationships as shown in inequalities (1) to (8). Ｎ-1 <SH Ｎ-2 <SH Ｎ-4 <SH Ｎ-7 <SH Ｎ-11 …(1) SH Ｎ-3 <SH Ｎ-5 <SH Ｎ-8 <SH Ｎ-12 …(2) SH Ｎ-6 <SH Ｎ-9 <SH Ｎ-13 …(3) SH Ｎ-10 <SH Ｎ-14 …(4) SH Ｎ-3 <SH Ｎ-2 …(5) SH Ｎ-6 <SH Ｎ-5 <SH Ｎ-4 …(6) SH Ｎ-10 <SH Ｎ-9 <SH Ｎ-8 <SH Ｎ-7 …(7) SH Ｎ-15 <SH Ｎ-14 <SH Ｎ-13 <SH Ｎ-12 <SH Ｎ-11 ...(8) In Figs. 5 and 6, if the column has the same evaporation temperature ET, the target value is SH ｍｉｎ SH up to a certain value of condensation temperature CT ｍｉｎIn the range where the condensing temperature is higher than this value, the higher the condensing temperature CT, the larger the target value SH. That is, in the map, for the same operating frequency f and the same evaporation temperature ET, the target value at the first condensing temperature is set to be equal to or higher than the target value at the second condensing temperature that is lower than the first condensing temperature.

[0042] Variation 1 of Embodiment 1: Regarding the target value of discharge SH, in cooling operation, control can be performed using a target value obtained by using the outside air temperature instead of CT and the average inlet / outlet water temperature instead of ET in the reference operation, and in heating operation, control can be performed using a target value obtained by using the average inlet / outlet water temperature Tave instead of CT and the outside air temperature Ta instead of ET in the reference operation.

[0043] Fig. 7 is a control flowchart of the injection expansion valve using the outside air temperature, the average inlet / outlet water temperature, and the compressor frequency according to Modification 1 of Embodiment 1. The flowchart of Fig. 7 includes the processing of steps ST50, ST51, and ST52 instead of steps ST5 and ST6 in the flowchart of the reference operation shown in Fig. 4. The processing of the other steps has been described in Fig. 4, so description thereof will not be repeated here.

[0044] 7, if the discharge SH is equal to or greater than the lower limit value (YES in ST3), the control device 100 determines in step ST50 whether the air conditioner is in cooling operation. If the air conditioner is in cooling operation (YES in ST50), the control device 100 executes the process of step ST51, and if the air conditioner is in heating operation (NO in ST50), the control device 100 executes the process of step ST52.

[0045] In step S51, the control device 100 obtains a target value of the discharge SH from a map for cooling operation, while in step S52, the control device 100 obtains a target value of the discharge SH from a map for heating operation.

[0046] Fig. 8 is a diagram showing a target value map (cooling operation, f = 100 Hz) of discharge SH using the outside air temperature Ta, the average inlet / outlet water temperature Tave, and the compressor frequency f according to Modification 1 of Embodiment 1. Fig. 9 is a diagram showing a target value map (cooling operation, f = 80 Hz) of discharge SH using the outside air temperature Ta, the average inlet / outlet water temperature Tave, and the compressor frequency f according to Modification 1 of Embodiment 1.

[0047] Fig. 10 is a diagram showing a target value map (heating operation, f = 100 Hz) of discharge SH using the outside air temperature Ta, the average inlet / outlet water temperature Tave, and the compressor frequency f according to Modification 1 of Embodiment 1. Fig. 11 is a diagram showing a target value map (heating operation, f = 80 Hz) of discharge SH using the outside air temperature Ta, the average inlet / outlet water temperature Tave, and the compressor frequency f according to Modification 1 of Embodiment 1. In Figs. 10 and 11, "↑" indicates SH. ｍｉｎ indicates that the value is the same as

[0048] In each of the above cooling operation maps and heating operation maps, the input values ​​are the outside air temperature Ta instead of CT and the inlet / outlet average water temperature Tave = (Tw1 + Tw2) / 2 instead of ET. Target values ​​of discharge SH preset for these input values ​​are stored in the maps.

[0049] The relationships of equations (1) to (8) also hold true in Figs. 8 to 11. In Figs. 8 and 9 showing the maps for cooling operation, in the same column of average temperature Tave, the target value is SH up to a certain value of outside air temperature Ta. ｍｉｎ In the range where the outside air temperature Ta is greater than this value, the higher the outside air temperature Ta, the larger the target value. That is, in the map, for the same operating frequency f and the same average temperature, the target value at a first outside air temperature is set to be equal to or greater than the target value at a second outside air temperature that is lower than the first outside air temperature.

[0050] 10 and 11 showing the maps for heating operation, if the row has the same outside air temperature, the target value is SH up to a certain average temperature. ｍｉｎIn the range where the average temperature is higher than this value, the target value increases as the average temperature Tave increases. In other words, in the map, for the same operating frequency and the same outside air temperature, the target value for the first average water temperature is set to be equal to or higher than the target value for the second average water temperature, which is lower than the first average water temperature.

[0051] According to variant example 1 shown in Figures 7 to 11, it is possible to control the third expansion valve 19 of the injection flow path F2 even when a non-azeotropic refrigerant mixture that has a temperature gradient and does not have a clear CT and ET is used as the refrigerant.

[0052] Modification 2 of Embodiment 1. The target value of the discharge SH can be obtained using the product C (= ΔT × Fw) of the inlet / outlet water temperature difference ΔT (= Tw2 - Tw1) and the water flow rate Fw, instead of the compressor frequency f in the reference operation. The product C of the inlet / outlet water temperature difference ΔT and the water flow rate has a one-to-one correspondence with the capacity of the refrigeration cycle. Therefore, it is possible to more accurately control the third expansion valve 19 of the injection flow path F2 according to the capacity.

[0053] Fig. 12 is a control flowchart of the injection expansion valve using the outside air temperature, the average inlet / outlet water temperature, and the product of the inlet / outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1. The flowchart of Fig. 12 includes the processing of steps ST50, ST61, and ST62 instead of steps ST5 and ST6 in the flowchart of the reference operation shown in Fig. 4. The processing of the other steps has been explained in Fig. 4, so the explanation will not be repeated here.

[0054] 12, if the discharge SH is equal to or greater than the lower limit value (YES in ST3), the control device 100 determines in step ST50 whether or not the air conditioner is in cooling operation. If the air conditioner is in cooling operation (YES in ST50), the control device 100 executes the process of step ST61, and if the air conditioner is in heating operation (NO in ST50), the control device 100 executes the process of step ST62.

[0055] In step S61, the control device 100 obtains a target value of the discharge SH from a map for cooling operation, while in step S62, the control device 100 obtains a target value of the discharge SH from a map for heating operation.

[0056] Fig. 13 is a diagram showing a target value map (cooling operation, f = 100 Hz) of discharge SH using the outside air temperature, the inlet / outlet average water temperature, and the product of the inlet / outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1. Fig. 14 is a diagram showing a target value map (cooling operation, f = 80 Hz) of discharge SH using the outside air temperature, the inlet / outlet average water temperature, and the product of the inlet / outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1.

[0057] Fig. 15 is a diagram showing a target value map (heating operation, f = 100 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the product of the inlet and outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1. Fig. 16 is a diagram showing a target value map (heating operation, f = 80 Hz) of discharge SH using the outside air temperature, the average inlet and outlet water temperature, and the product of the inlet and outlet water temperature difference and the water flow rate according to Modification 2 of Embodiment 1.

[0058] In each of the above maps for cooling operation and heating operation, the input values ​​are the outside air temperature Ta instead of CT, the inlet / outlet average water temperature Tave = (Tw1 + Tw2) / 2 instead of ET, and the product C (= (Tw2 - Tw1) × Fw) of the inlet / outlet water temperature difference and the water flow rate instead of the compressor frequency f, and a preset target value for discharge SH is stored.

[0059] The relationships of equations (1) to (8) also hold true in Figures 13 to 16. According to Modification 2 shown in Figures 12 to 16, even when a non-azeotropic refrigerant mixture with a temperature gradient and no clear CT or ET is used as the refrigerant, it is possible to control the third expansion valve 19 injection expansion valve, and the input value is a parameter that has a one-to-one relationship with the heating or cooling capacity of the heat pump, namely, the product of the temperature change and the flow rate of the liquid medium heated or cooled in the third heat exchanger 17. This makes it possible to control the third expansion valve 19 of the injection flow path F2 using a target value with improved accuracy.

[0060] As described above, according to the first embodiment, the injection expansion valve is controlled using a predetermined target value so as to minimize the exergy loss, thereby making it possible to expect high efficiency of the heat pump.

[0061] Embodiment 2. Fig. 17 is a refrigerant circuit diagram of a heat pump device according to embodiment 2. The heat pump device 2 shown in Fig. 17 is different from the heat pump device 1 of embodiment 1 in that a pressure sensor 113 is added to the injection flow path F2 at a position between the second heat exchanger 15 and the compressor 11. The control device 100 also receives an intermediate pressure PM detected by the pressure sensor 113 as an input value. The other configuration is the same as the configuration shown in Fig. 1, and therefore description thereof will not be repeated here.

[0062] Fig. 18 is a control flowchart of the injection expansion valve according to embodiment 2. The processing of the flowchart in Fig. 18 differs from the reference operation (the flow in Fig. 4) in that the third expansion valve 19 of the injection flow path F2 is controlled using the intermediate pressure PM as a target value.

[0063] The flowchart of Fig. 18 includes steps ST15 and ST16 instead of steps ST5 and ST6 in the flowchart of the reference operation shown in Fig. 4. The processes of the other steps have been described in Fig. 4, so description thereof will not be repeated here.

[0064] If the discharge SH is equal to or greater than the lower limit value in step ST3 (YES in ST3), in step S15, the control device 100 acquires a target value from the map of target values ​​for the intermediate pressure PM instead of the target value map for the discharge SH, and in the subsequent step ST16, the control device 100 controls the third expansion valve 19 in the injection flow path F2 so that the intermediate pressure PM becomes equal to the acquired target value.

[0065] Fig. 19 is a diagram showing a target value map (f=100 Hz) of the intermediate pressure PM used in the second embodiment. Fig. 20 is a diagram showing a target value map (f=80 Hz) of the intermediate pressure PM used in the second embodiment.

[0066] Here, the map number is represented by K, and the map numbers in FIG. 19 and FIG. 20 are K=1 and K=2, respectively, and the target value of the intermediate pressure is P Ｋ－Ｍ Let's say. Ｋ－Ｍ In the above equations, K indicates the map number, and M indicates the target value number in each map. In each map, the target values ​​have the following magnitude relationships as shown in inequalities (9) to (18). Ｋ-1 <P Ｋ-2 <P Ｋ-3 <P Ｋ-4 <P Ｋ-5 …(9) P Ｋ-6 <P Ｋ-7 <P Ｋ-8 <P Ｋ-9 <P Ｋ-10 …(10) P Ｋ-11 <P Ｋ-12 <P Ｋ-13 <P Ｋ-14 <P Ｋ-15 …(11) P Ｋ-16 <P Ｋ-17 <P Ｋ-18 <P Ｋ-19 <P Ｋ-20 …(12) P Ｋ-21 <P Ｋ-22 <P Ｋ-23 <P Ｋ-24 <P Ｋ-25 …(13) P Ｋ-1 <P Ｋ-6 <P Ｋ-11 <P Ｋ-16 <P Ｋ-21 …(14) P Ｋ-2 <P Ｋ-7 <P Ｋ-12 <P Ｋ-17 <P Ｋ-22 …(15) P Ｋ-3 <P Ｋ-8 <P Ｋ-13 <P Ｋ-18 <P Ｋ-23 …(16) P Ｋ-4 <P Ｋ-9 <P Ｋ-14 <P Ｋ-19 <P Ｋ-24 …(17) P Ｋ-5 <P Ｋ-10 <P Ｋ-15 <P Ｋ-20 <P Ｋ-25...(18) The discharge SH depends not only on the refrigerant state at the injection suction port (G3) but also on the refrigerant state at the compressor suction port (G1). Therefore, even if the third expansion valve 19 of the injection flow path F2 is controlled based on the target value of the discharge SH as in the first embodiment, it is not necessarily possible to operate at an optimal opening.

[0067] On the other hand, the intermediate pressure PM has a one-to-one relationship with the injection refrigerant flow rate at which the exergy loss is minimized. Therefore, the heat pump apparatus of the second embodiment enables more accurate control of the expansion valve 19 of the injection flow path F2 than the first embodiment.

[0068] Embodiment 3 Fig. 21 is a refrigerant circuit diagram of a heat pump device according to embodiment 3. The heat pump device 3 shown in Fig. 21 has a three-stage compression compressor 210 instead of the two-stage compression compressor 11 of the refrigerant circuit configuration of embodiment 1 shown in Fig. 1, and further includes a fourth heat exchanger 21.

[0069] The compressor 210 includes a low-stage compression mechanism 210L that compresses the refrigerant heated in the third heat exchanger 17, a middle-stage compression mechanism 210M that further compresses the refrigerant pressurized to a first intermediate pressure in the low-stage compression mechanism 210L, and a high-stage compression mechanism 210H that further compresses the refrigerant pressurized to a second intermediate pressure in the middle-stage compression mechanism 210M.

[0070] The fourth heat exchanger 21 is configured to exchange heat between the refrigerant flowing through the passage H3 and the refrigerant flowing through the passage H4. The passage H3 is disposed in the refrigerant circulation path F1 between the passage H1 of the second heat exchanger and the second expansion valve 16.

[0071] Furthermore, an injection flow path F3 branches off from the injection flow path F2. The injection flow path F3 branches off from the suction side G3 of the high-stage compression mechanism 210H of the compressor 210, and passes through the pressure reducing device 20 and a passage H4 of the fourth heat exchanger 21 to reach the suction side (G4) of the middle-stage compression mechanism 210M of the compressor 11. The pressure reducing device 20 may be, for example, a capillary tube.

[0072] Regarding the control of the third expansion valve 19 of the injection flow path F2, the same control method as the reference operation shown in FIG. 4 may be applied, and therefore the description thereof will not be repeated here.

[0073] The heat pump unit 3 shown in Fig. 21 may be combined with the control of the flowchart of Fig. 7 or 12. Furthermore, the heat pump unit 3 shown in Fig. 21 may be combined with the control of the flowchart of Fig. 18 by adding a pressure sensor that detects the intermediate pressure PM.

[0074] In the heat pump device of embodiment 3, by injecting in two stages, it is possible to reduce exergy loss even more than in the heat pump devices of embodiments 1 and 2, and to achieve more efficient operation.

[0075] [Summary] The present disclosure will be summarized again with reference to the drawings.

[0076] (Section 1) The present disclosure relates to a heat pump apparatus 1 that exchanges heat with a user-side device. As shown in FIG. 1 , the heat pump apparatus 1 includes a refrigerant circulation path F1 in which a refrigerant flows, and in which a compressor 11, a first heat exchanger 13, a first expansion valve 14, a second heat exchanger 15, a second expansion valve 16, and a third heat exchanger 17 are connected in a ring shape. The first heat exchanger 13 is configured to exchange heat between the refrigerant and outside air. The second heat exchanger 15 is configured to exchange heat between refrigerants. The third heat exchanger 17 is configured to exchange heat between the refrigerant and a liquid medium used in the user-side device. The compressor 11 includes a first compression mechanism 11L that compresses the refrigerant heated by the third heat exchanger and a second compression mechanism 11H that further compresses the refrigerant pressurized by the first compression mechanism 11L. The heat pump apparatus 1 further includes a first injection path F2 that includes a third expansion valve 19. The first injection flow path F2 returns a portion of the refrigerant cooled in the first heat exchanger 13 to the suction side of the second compression mechanism 11H via the third expansion valve 19 and the second heat exchanger 15. The second heat exchanger 15 is configured to perform heat exchange between the refrigerant cooled in the first heat exchanger 13 and the refrigerant decompressed by the third expansion valve 19. The heat pump device 1 further includes a control device 100 configured to observe the state of the refrigerant circulation path F1 and control the opening degree of the third expansion valve 19 in accordance with the observation result.

[0077] (Item 2) In the heat pump apparatus described in item 1, as shown in Fig. 4, the control device 100 is configured to control the third expansion valve 19 so as to bring the degree of superheat of the refrigerant discharged from the compressor 11 closer to a target value obtained using a map. As shown in Fig. 5 and Fig. 6, the map is configured to output a target value SH from three variables: the refrigerant condensation temperature CT, the refrigerant evaporation temperature ET, and the compressor operating frequency f.

[0078] (Clause 3) In the heat pump device described in clause 2, as shown in Figures 5 and 6, in the map, if the operating frequency and evaporation temperature are the same, the target value at the first condensing temperature is set to be equal to or higher than the target value at the second condensing temperature which is lower than the first condensing temperature.

[0079] (Item 4) In the heat pump apparatus described in item 1, as shown in Fig. 7, the control device 100 is configured to control the third expansion valve 19 so as to bring the degree of superheat SH of the refrigerant discharged from the compressor 11 closer to a target value obtained using a map. As shown in Figs. 8 to 11, the map is configured to output the target value SH from three variables: the outside air temperature Ta, the average temperature Tave of the liquid medium in the third heat exchanger, and the operating frequency f of the compressor.

[0080] (Item 5) In the heat pump device described in item 4, as shown in Figures 8 and 9, when the heat pump device performs cooling operation, in the map, if the operating frequency and average temperature are the same, the target value at the first outdoor air temperature is set to be higher than the target value at the second outdoor air temperature that is lower than the first outdoor air temperature.

[0081] (Item 6) In the heat pump device described in Item 5, as shown in Figures 10 and 11, when the heat pump device performs heating operation, in the map, if the operating frequency and the outside air temperature are the same, the target value at the first average temperature is set to be equal to or higher than the target value at the second average temperature which is lower than the first average temperature.

[0082] (Item 7) In the heat pump apparatus described in item 1, as shown in Fig. 12, the control device 100 is configured to control the third expansion valve 19 so as to bring the degree of superheat of the refrigerant discharged from the compressor 11 closer to a target value obtained using a map. As shown in Figs. 13 to 16, the map is configured to output a target value SH from three variables: the outside air temperature Ta, the average temperature Tave of the liquid medium in the third heat exchanger, and the product of the flow rate Fw of the liquid medium flowing through the third heat exchanger and the difference between the inlet temperature Tw1 and the outlet temperature Tw2 of the liquid medium flowing through the third heat exchanger.

[0083] (Item 8) In the heat pump device described in Item 7, as shown in Figures 13 and 14, when the heat pump device is operating in cooling mode, if the product of the differences is the same and the average temperature is the same in the map, the target value at a first outdoor air temperature is set to be higher than the target value at a second outdoor air temperature that is lower than the first outdoor air temperature.

[0084] (Item 9) In the heat pump device described in Item 8, when the heat pump device performs heating operation as shown in Figures 15 and 16, in the map, if the product of the differences is the same and the outdoor air temperature is the same, the target value at the first average temperature is set to be equal to or higher than the target value at the second average temperature which is lower than the first average temperature.

[0085] (Item 10) In the heat pump apparatus described in item 1, the control device 100 is configured to control the third expansion valve 19 so that the pressure of the refrigerant passing through the first injection flow path F2 approaches a target value obtained using a map, as shown in Fig. 18. The map is configured to output a target value from three variables, namely, the refrigerant condensation temperature CT, the refrigerant evaporation temperature ET, and the compressor operating frequency f, as shown in Fig. 19 and Fig. 20.

[0086] (Item 11) In the heat pump apparatus described in item 10, as shown in Figures 19 and 20, in the map, if the operating frequency and the evaporation temperature are the same, the target value at the first condensing temperature is set to be equal to or higher than the target value at the second condensing temperature that is lower than the first condensing temperature. Furthermore, if the operating frequency and the condensing temperature are the same, the target value at the first evaporation temperature is set to be equal to or higher than the target value at the second evaporation temperature that is lower than the first evaporation temperature.

[0087] 21 , in the heat pump apparatus described in paragraph 1, compressor 210 further includes a third compression mechanism 210M that is disposed between first compression mechanism 210L and second compression mechanism 210H and that further compresses the refrigerant compressed in first compression mechanism 210L and supplies the refrigerant to second compression mechanism 210H. The heat pump apparatus further includes: a fourth heat exchanger 21 that is disposed in refrigerant circulation path F1 between second heat exchanger 15 and second expansion valve 16; a second injection path F3 that branches from a branching point in first injection path F2 and passes through fourth heat exchanger 21 to an intake part of third compression mechanism 210M of compressor 210; and a pressure reducing device 20 that is disposed in second injection path F3 between the branching point and fourth heat exchanger 21. The fourth heat exchanger 21 is configured to exchange heat between the refrigerant flowing through the refrigerant circulation path F1 cooled by the second heat exchanger 15 and the refrigerant flowing through the second injection path F3 decompressed by the pressure reducing device 20. The control device 100 is configured to control the third expansion valve 19 so that the degree of superheat of the refrigerant discharged from the compressor approaches a target value obtained using a map. The map is configured to output a target value SH from three variables: the refrigerant condensation temperature CT, the refrigerant evaporation temperature ET, and the compressor operating frequency f.

[0088] (Item 13) In the heat pump device described in any one of Items 2 to 12, the control device 100 is configured to control the third expansion valve (ST2) when the discharge temperature TH of the compressor 11 is higher than the target value so that the discharge temperature does not exceed the target value.

[0089] (14) In the heat pump device described in any one of paragraphs 2 to 13, the map is configured to output a predetermined superheat degree SH or a predetermined intermediate pressure PM of the discharged refrigerant as a target value so that exergy loss is minimized.

[0090] (15th Item) In the heat pump apparatus according to any one of the first to fourteenth items, the refrigerant filled in the refrigerant circulation path F1 is a non-azeotropic refrigerant mixture.

[0091] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0092] 1, 2, 3 Heat pump device, 11, 210 Compressor, 11H, 11L, 210H, 210M, 210L Compression mechanism, 12 Four-way valve, 13 First heat exchanger, 13F Fan, 14 First expansion valve, 15 Second heat exchanger, 16 Second expansion valve, 17 Third heat exchanger, 18 Accumulator, 19 Third expansion valve, 20 Pressure reducing device, 21 Fourth heat exchanger, 80, 81, 82, 88, 91, 92, 93 Piping, 100 Control device, 102 CPU, 104 Memory, 110, 111, 113 Pressure sensor, 120, 121, 122, 123 Temperature sensor, 124 Flow rate sensor, F1 Refrigerant circulation path, F2, F3 Injection path, G1 Intake port, G2 Discharge port, G3 Intermediate pressure port, H1, H2, H3, H4 passages.

Claims

1. A heat pump device that exchanges heat with a user-side device, comprising a compressor, a first heat exchanger, a first expansion valve, a second heat exchanger, a second expansion valve, and a third heat exchanger connected in a ring, and a refrigerant circulation path through which a refrigerant flows, the first heat exchanger being configured to exchange heat between the refrigerant and outside air, the second heat exchanger being configured to exchange heat between the refrigerants themselves, and the third heat exchanger being configured to exchange heat between the refrigerant and a liquid medium used in the user-side device, the compressor comprising a first compression mechanism that compresses the refrigerant heated in the third heat exchanger, and a second compression mechanism that further compresses the refrigerant pressurized by the first compression mechanism, the heat pump device further comprising a third expansion valve, and a first injection flow path that returns a portion of the refrigerant cooled in the first heat exchanger to the suction side of the second compression mechanism via the third expansion valve and the second heat exchanger, the second heat exchanger is configured to perform heat exchange between the refrigerant cooled in the first heat exchanger and the refrigerant decompressed in the third expansion valve, and the heat pump device further includes a control device configured to observe a state of the refrigerant circulation path and control the opening degree of the third expansion valve in accordance with the observation result.

2. The heat pump device of claim 1, wherein the control device is configured to control the third expansion valve so as to bring the degree of superheat of the refrigerant discharged from the compressor closer to a target value obtained using a map, and the map is configured to output the target value from three variables: the condensation temperature of the refrigerant, the evaporation temperature of the refrigerant, and the operating frequency of the compressor.

3. A heat pump device as described in claim 2, wherein in the map, for the same operating frequency and the same evaporation temperature, the target value at the first condensing temperature is set to be equal to or higher than the target value at the second condensing temperature which is lower than the first condensing temperature.

4. The heat pump device of claim 1, wherein the control device is configured to control the third expansion valve so as to bring the degree of superheat of the refrigerant discharged from the compressor closer to a target value obtained using a map, and the map is configured to output the target value from three variables: outside air temperature, average temperature of the liquid medium in the third heat exchanger, and operating frequency of the compressor.

5. A heat pump device as described in claim 4, wherein, when the heat pump device is performing cooling operation, in the map, if the operating frequency and average temperature are the same, the target value at a first outdoor air temperature is set to be equal to or higher than the target value at a second outdoor air temperature that is lower than the first outdoor air temperature.

6. A heat pump device as described in claim 5, wherein, when the heat pump device performs heating operation, in the map, if the operating frequency and the outside air temperature are the same, the target value at a first average temperature is set to be equal to or higher than the target value at a second average temperature that is lower than the first average temperature.

7. The heat pump device of claim 1, wherein the control device is configured to control the third expansion valve so as to bring the degree of superheat of the refrigerant discharged from the compressor closer to a target value obtained using a map, and the map is configured to output the target value from three variables: outside air temperature, average temperature of the liquid medium in the third heat exchanger, and the product of the flow rate of the liquid medium flowing through the third heat exchanger and the difference between the inlet temperature and the outlet temperature of the liquid medium flowing through the third heat exchanger.

8. A heat pump device as described in claim 7, wherein when the heat pump device is performing cooling operation, if the product of the differences is the same and the average temperature is the same in the map, the target value at a first outdoor air temperature is set to be equal to or higher than the target value at a second outdoor air temperature that is lower than the first outdoor air temperature.

9. The heat pump device of claim 8, wherein when the heat pump device is performing heating operation, in the map, for the same product of differences and the same outdoor temperature, the target value at a first average temperature is set to be equal to or higher than the target value at a second average temperature that is lower than the first average temperature.

10. The heat pump device of claim 1, wherein the control device is configured to control the third expansion valve so as to bring the pressure of the refrigerant passing through the first injection flow path closer to a target value obtained using a map, and the map is configured to output the target value from three variables: the condensation temperature of the refrigerant, the evaporation temperature of the refrigerant, and the operating frequency of the compressor.

11. A heat pump device as described in claim 10, wherein, in the map, for the same operating frequency and the same evaporating temperature, the target value at a first condensing temperature is set to be equal to or higher than the target value at a second condensing temperature that is lower than the first condensing temperature, and, for the same operating frequency and the same condensing temperature, the target value at the first evaporating temperature is set to be equal to or higher than the target value at a second evaporating temperature that is lower than the first evaporating temperature.

12. The compressor further includes a third compression mechanism disposed between the first compression mechanism and the second compression mechanism, further compressing the refrigerant compressed by the first compression mechanism and supplying the refrigerant to the second compression mechanism; the heat pump device further includes a fourth heat exchanger disposed in the refrigerant circulation path between the second heat exchanger and the second expansion valve; a second injection path branching from a branching portion in the first injection path and passing through the fourth heat exchanger to an intake portion of the third compression mechanism of the compressor; and a pressure reducing device disposed in the second injection path between the branching portion and the fourth heat exchanger; the fourth heat exchanger is configured to exchange heat between the refrigerant flowing in the refrigerant circulation path cooled by the second heat exchanger and the refrigerant flowing in the second injection path decompressed by the pressure reducing device; and the control device is configured to control the third expansion valve so as to bring the degree of superheat of the refrigerant discharged from the compressor close to a target value obtained using a map. The heat pump apparatus according to claim 1 , wherein the map is configured to output the target value from three variables: a condensation temperature of the refrigerant, an evaporation temperature of the refrigerant, and an operating frequency of the compressor.

13. The heat pump device according to any one of claims 2 to 12, wherein the control device is configured to control the third expansion valve when the discharge temperature of the compressor is higher than the target value so that the discharge temperature does not exceed the target value.

14. A heat pump device according to any one of claims 2 to 13, wherein the map is configured to output as the target value a predetermined degree of superheat of the discharged refrigerant or a predetermined intermediate pressure that minimizes exergy loss.

15. A heat pump device according to any one of claims 1 to 14, wherein the refrigerant filled in the refrigerant circulation path is a non-azeotropic refrigerant mixture.

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