JP2021092358A - Heat pump system - Google Patents

Abstract

To provide a heat pump system which can curb a reduction in a COP through appropriate control even with an increase in a temperature of a user side heat medium flowing into a user side heat exchanger.SOLUTION: A heat pump system comprises: a main refrigerant circuit 10 made up of a compressing mechanism 11, a user side heat exchanger 12, an intermediary heat exchanger 13, a first expansion device 14, a heat source side heat exchanger 15; a bypass refrigerant circuit 20 which branches a refrigerant from piping 16 between the user side heat exchanger 12 and the first expansion device 14, allows the branched refrigerant to undergo decompression with a second expansion device 21 and to exchange heat with the refrigerant flowing in the main refrigerant circuit 10 through the intermediary heat exchanger 13, and merges the same into the refrigerant in the middle of undergoing compression with a compressive rotary element; and a control device 60. When a temperature of a heat medium flowing into the user side heat exchanger 12 is increased, the control device 60 controls at least a valve opening of the second expansion device 21 so as to increase a ratio of a flow rate of the refrigerant flowing in the bypass refrigerant circuit 20 to the flow rate of the refrigerant flowing in the intermediary heat exchanger 13 at the side of the main refrigerant circuit 10.SELECTED DRAWING: Figure 3

Description

The present invention relates to a heat pump system in which the high pressure side operates at a supercritical pressure.

Conventionally, this type of refrigeration cycle device uses a refrigerant having a supercritical pressure on the high pressure side, a two-stage compressor, a heat exchanger for heating hot water, a cooler, a first electric expansion valve, and evaporation. It is branched from the refrigerant circuit formed by connecting the vessels in a ring shape with a refrigerant pipe and the refrigerant circuit between the heating heat exchanger and the cooler, and has a second electric expansion valve and the cooler in the middle. Some of them are provided with an intermediate injection circuit that returns a part of the refrigerant discharged from the heating heat exchanger to the middle between the low pressure side and the high pressure side of the compressor.

Then, the first temperature detection sensor that detects the refrigerant discharge temperature on the high pressure side of the compressor, the second temperature detection sensor that detects the refrigerant temperature at the outlet of the heating heat exchanger, and the refrigerant temperature at the outlet of the cooler are measured. When the detection temperature of the third temperature detection sensor to be detected and the detection temperature of the first temperature detection sensor is within the first predetermined temperature range, the opening degree of the first electric expansion valve is controlled to be maintained and the first is controlled. (2) When the difference between the detection temperature of the temperature detection sensor and the detection temperature of the third temperature detection sensor is within the second predetermined temperature range, control is performed so as to maintain the opening degree of the second electric expansion valve. Therefore, the amount of refrigerant circulating in the intermediate injection circuit is suppressed within a certain range to realize the formation of the assumed refrigeration cycle.

When the heating load of the heating device becomes lighter, the return temperature of the water from the hot water circuit to the heating heat exchanger rises, and the refrigerant discharge temperature of the high-stage rotary compression element also rises, so that the first electric expansion valve Is opened to control the refrigerant discharge temperature of the high-stage rotary compression element (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-008499

However, in the conventional configuration, in a refrigeration cycle apparatus having a heating heat exchanger for heating hot water and an intermediate injection circuit and having a supercritical pressure on the high pressure side, the return temperature of water to the heating heat exchanger has increased. Occasionally, the COP of the refrigeration cycle apparatus also decreases, but there is a problem that the technology for suppressing the COP is not disclosed.

The present invention solves the above-mentioned conventional problems, and even if the temperature of the user-side heat medium flowing into the user-side heat exchanger rises, the high-pressure side that suppresses the decrease in COP by performing appropriate control is supercritical. It is an object of the present invention to provide a heat pump system that operates at a critical pressure.

In order to solve the above-mentioned conventional problems, the heat pump system of the present invention has a compression mechanism composed of a compression rotation element, and a utilization side that heats a heat medium on the utilization side with a refrigerant discharged from the compression rotation element and exceeding a critical pressure. A main refrigerant circuit formed by sequentially connecting a heat exchanger, an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger with pipes, and between the utilization side heat exchanger and the first expansion device. After the refrigerant branched from the pipe is decompressed by the second expansion device, the intermediate heat exchanger exchanges heat with the refrigerant flowing through the main refrigerant circuit and joins the refrigerant in the process of compression of the compression rotating element. A bypass refrigerant circuit and a control device are provided, and the control device is provided with at least a valve opening degree of the second expansion device when the temperature of the utilization side heat medium flowing into the utilization side heat exchanger rises. Is characterized by increasing the ratio of the amount of the refrigerant flowing through the bypass refrigerant circuit to the amount of the refrigerant flowing through the main refrigerant circuit side of the intermediate heat exchanger.

As a result, even if the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger rises, the amount of the bypass refrigerant circuit, the high-stage compression rotating element, and the refrigerant circulating in the utilization-side heat exchanger increases. It is possible to suppress a decrease in the heating capacity of the heat exchanger on the user side.

Further, even when the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger rises, the amount of heat exchange between the high-pressure refrigerant flowing through the main refrigerant circuit and the intermediate-pressure refrigerant flowing through the bypass refrigerant circuit in the intermediate heat exchanger increases. Therefore, it is possible to suppress a decrease in the enthalpy difference between the refrigerant outlet and the refrigerant inlet in the user-side heat exchanger.

Therefore, even if the temperature of the heat medium on the user side flowing into the heat exchanger on the user side rises, it is possible to provide a heat pump system in which the high pressure side that suppresses the decrease in COP operates at supercritical pressure.

According to the present invention, even if the temperature of the heat medium on the user side flowing into the heat exchanger on the user side rises, a heat pump system in which the high pressure side, which suppresses the decrease in COP by performing appropriate control, operates at supercritical pressure is provided. Can be provided.

Configuration diagram of the heat pump system according to the first embodiment of the present invention Pressure-enthalpy diagram (Ph diagram) of the refrigeration cycle apparatus according to the first embodiment of the present invention. In the heat pump system according to the first embodiment of the present invention, the pressure-enthalpy diagram (Ph diagram) of the refrigeration cycle apparatus when the temperature of the utilization side heat medium flowing into the utilization side heat exchanger rises.

The first invention is a compression mechanism composed of a compression rotation element, a utilization side heat exchanger that heats a utilization side heat medium with a refrigerant discharged from the compression rotation element and exceeding a critical pressure, an intermediate heat exchanger, and the first. The main refrigerant circuit formed by sequentially connecting the expansion device and the heat source side heat exchanger with pipes, and the refrigerant branched from the pipe between the utilization side heat exchanger and the first expansion device are branched. After the pressure is reduced by the second expansion device, the intermediate heat exchanger exchanges heat with the refrigerant flowing through the main refrigerant circuit, and the bypass refrigerant circuit joins the refrigerant in the process of compression of the compression rotating element, the control device, and the control device. When the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger rises, the control device controls at least the valve opening degree of the second expansion device to control the valve opening degree of the intermediate heat exchanger. The heat pump system is characterized in that the ratio of the amount of the refrigerant flowing through the bypass refrigerant circuit to the amount of the refrigerant flowing on the main refrigerant circuit side is increased.

As a result, even if the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger rises, the amount of heat exchange between the high-pressure refrigerant flowing through the main refrigerant circuit and the intermediate-pressure refrigerant flowing through the bypass refrigerant circuit in the intermediate heat exchanger remains. Since the number increases, it is possible to suppress a decrease in the enthalpy difference between the refrigerant outlet and the refrigerant inlet in the user-side heat exchanger.

Further, since the amount of the refrigerant circulating in the bypass refrigerant circuit, the high-stage compression rotating element, and the utilization side heat exchanger increases, it is possible to suppress a decrease in the heating capacity of the utilization side heat exchanger.

Therefore, even if the temperature of the heat medium on the user side flowing into the heat exchanger on the user side rises, it is possible to provide a heat pump system in which the high pressure side that suppresses the decrease in COP operates at supercritical pressure.

The second invention, in particular, in the first invention, includes a heat medium inlet temperature thermistor for detecting the temperature of the user-side heat medium flowing into the user-side heat exchanger, and the detection temperature of the heat medium inlet temperature thermistor. When the temperature rises, the control device is characterized in that the valve opening degree of the second expansion device is increased.

As a result, even if the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger rises, the amount of the bypass refrigerant circuit, the high-stage compression rotating element, and the refrigerant circulating in the utilization-side heat exchanger increases. It is possible to suppress a decrease in the heating capacity of the heat exchanger on the user side.

A third invention, in particular, in the second invention, is characterized in that the control device reduces the valve opening degree of the first expansion device.

As a result, the pressure on the high-pressure side of the refrigerant in the main refrigerant circuit rises, so even if the temperature of the use-side heat medium flowing into the use-side heat exchanger rises, the refrigerant outlet and the refrigerant in the use-side heat exchanger It is possible to suppress a decrease in the enthalpy difference from the entrance.

A fourth invention, in particular, in the third invention, includes a discharge temperature thermistor that detects the temperature of the refrigerant discharged from the compression rotating element, and the control device is a valve opening degree of the first expansion device. By adjusting the valve opening degree of the second expansion device, the temperature detected by the discharge temperature thermistor is brought closer to the target value.

As a result, the high-pressure refrigerant flowing through the main refrigerant circuit and the intermediate-pressure refrigerant flowing through the bypass refrigerant circuit in the intermediate heat exchanger are prevented from being excessively increased or decreased by detecting the temperature of the refrigerant discharged from the compression rotating element. It is possible to increase the amount of heat exchange with and the amount of refrigerant circulating in the bypass refrigerant circuit, the high-stage compression rotating element, and the user-side heat exchanger.

Therefore, while achieving a stable refrigerant discharge temperature, even if the temperature of the user-side heat medium flowing into the user-side heat exchanger rises, the enthalpy between the refrigerant outlet and the refrigerant inlet in the user-side heat exchanger. It is possible to suppress the reduction of the difference and the reduction of the heating capacity in the heat exchanger on the user side.

A fifth invention, in particular, in the third invention, includes a high-pressure side pressure detecting device that detects the pressure of the refrigerant discharged from the compression rotating element, and the control device is a valve opening of the first expansion device. By adjusting the degree and the valve opening degree of the second expansion device, the pressure value detected by the high pressure side pressure detecting device is brought closer to the target value.

This prevents the pressure of the refrigerant discharged from the compression rotating element from rising or falling excessively, and even if the temperature of the heat medium on the user side flowing into the heat exchanger on the user side rises, the heat exchanger on the user side It is possible to suppress a decrease in the enthalpy difference between the refrigerant outlet and the refrigerant inlet.

The sixth invention is characterized in that, in particular, in any one of the first to fifth inventions, the transport device is provided, and the utilization side heat medium circuit for circulating the utilization side heat medium by the transfer device is provided. It is a heat pump system.

According to this, even if the temperature of the utilization side heat medium flowing into the utilization side heat exchanger rises, the decrease in COP is suppressed, and the high pressure side that can utilize the high temperature utilization side heat medium operates at supercritical pressure. Can provide a system.

The seventh invention is characterized in that, in any one of the first to sixth inventions, the heat medium on the utilization side is water or antifreeze.

This makes it possible to provide, for example, a heat pump system in which high-temperature water can be stored in a hot water storage tank, and the high-pressure side that heats using the high-temperature water operates at a supercritical pressure.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment.

(Embodiment 1)
FIG. 1 is a configuration diagram of a heat pump system according to the first embodiment of the present invention. The heat pump system includes a refrigeration cycle apparatus 9 which is a supercritical vapor compression refrigeration cycle, and a heat medium circuit 30 on the user side. Further, the refrigeration cycle device 9 is composed of a main refrigerant circuit 10 and a bypass refrigerant circuit 20.

In the main refrigerant circuit 10, the compression mechanism 11 for compressing the refrigerant, the utilization side heat exchanger 12 which is a radiator, the intermediate heat exchanger 13, the first expansion device 14, and the heat source side heat exchanger 15 which is an evaporator are connected to each other. It is formed by being sequentially connected at 16, and uses _{carbon dioxide (CO 2) as a refrigerant.}

The compression mechanism 11 is composed of a low-stage compression rotation element 11a and a high-stage compression rotation element 11b. The user-side heat exchanger 12 heats the user-side heat medium with the refrigerant discharged from the high-stage compression rotating element 11b.

The volume ratio of the low-stage compression rotation element 11a and the high-stage compression rotation element 11b constituting the compression mechanism 11 is constant, and the drive shafts (not shown) are shared and arranged in one container. It consists of one compressor.

In the present embodiment, the compression rotation element will be described using the two-stage compression mechanism 11 composed of the low-stage side compression rotation element 11a and the high-stage side compression rotation element 11b. The rotation element 11a and the high-stage compression rotation element 11b are not separated, and can be applied to a single compression rotation element.

Here, in the case of a single compression rotation element, the position where the refrigerant from the bypass refrigerant circuit 20 merges is in the middle of compression of the compression rotation element, and the compression rotation element up to the position where the refrigerant from the bypass refrigerant circuit 20 merges. Can be applied as the high-stage side compression rotation element 11b, and the compression rotation element after the position where the refrigerant from the bypass refrigerant circuit 20 merges can be applied as the high-stage side compression rotation element 11a.

Further, the two-stage compression mechanism 11 in which the low-stage compression rotation element 11a and the high-stage compression rotation element 11b are each composed of two independent compressors may be used.

The bypass refrigerant circuit 20 is branched from the pipe 16 between the heat exchanger 12 on the utilization side and the first expansion device 14, and is connected to the pipe 16 between the compression rotation element 11a on the low stage side and the compression rotation element 11b on the high stage side. It is connected.

The bypass refrigerant circuit 20 is provided with a second expansion device 21. After the part of the high-pressure refrigerant after passing through the user-side heat exchanger 12 or the part of the high-pressure refrigerant after passing through the intermediate heat exchanger 13 is decompressed by the second expansion device 21 to become an intermediate-pressure refrigerant. , The intermediate heat exchanger 13 exchanges heat with the high-pressure refrigerant flowing through the main refrigerant circuit 10, and merges with the refrigerant between the low-stage compression rotating element 11a and the high-stage compression rotating element 11b.

The user-side heat medium circuit 30 is formed by sequentially connecting the user-side heat exchanger 12, the transfer device 31 as a transfer pump, and the heating terminal 32a with a heat medium pipe 33, and uses water or antifreeze as the user-side heat medium. ing.

The user-side heat medium circuit 30 in the present embodiment includes a hot water storage tank 32b in parallel with the heating terminal 32a, and by switching between the first switching valve 34 and the second switching valve 35, the user-side heat medium is switched to the heating terminal 32a. Alternatively, it is circulated in the hot water storage tank 32b. The user-side heat medium circuit 30 may include either the heating terminal 32a or the hot water storage tank 32b.

The high-temperature water generated by the user-side heat exchanger 12 is radiated by the heating terminal 32a and used for heating, and the low-temperature water radiated by the heating terminal 32a is heated again by the user-side heat exchanger 12.

Further, the high temperature water generated by the user side heat exchanger 12 is introduced into the hot water storage tank 32b from the upper part of the hot water storage tank 32b, and the low temperature water is derived from the lower part of the hot water storage tank 32b and heated by the user side heat exchanger 12. To.

The hot water supply heat exchanger 42 is arranged in the hot water storage tank 32b, and heats are exchanged between the water supply from the water supply pipe 43 and the high temperature water in the hot water storage tank 32b. That is, when the hot water supply plug 41 is opened, water is supplied from the water supply pipe 43 into the hot water supply heat exchanger 42, heated by the hot water supply heat exchanger 42, and adjusted to reach a predetermined temperature by the hot water supply plug 41. , Hot water is supplied from the hot water tap 41.

The hot water supplied from the water supply pipe 43, heated by the hot water heat exchanger 42, and supplied from the hot water tap 41 and the high temperature water in the hot water storage tank 32b are indirect heating that do not mix with each other. ..

The hot water supply heat exchanger 42 is a water heat exchanger that uses a copper pipe or a stainless steel pipe as a heat transfer pipe, and as shown in FIG. 1, a water supply pipe 43 extending from a water supply source (water supply) and a hot water tap 41. Is connected. The water supply pipe 43 puts water at room temperature into the lower end of the hot water supply heat exchanger 42, that is, below the inside of the hot water storage tank 32b.

The room temperature water that has entered the hot water supply heat exchanger 42 from the water supply pipe 43 moves from the bottom to the top in the hot water storage tank 32b, removes heat from the high temperature water in the hot water storage tank 32b, and becomes the heated high temperature heated water. Hot water is supplied from the hot water tap 41.

The hot water storage tank 32b includes, for example, a plurality of first hot water storage tank temperature thermistors 55a, a second hot water storage tank temperature thermistor 55b, and a third hot water storage tank temperature thermistor 55c for the purpose of measuring the temperature of hot water at a plurality of different height positions. It is provided.

The room temperature water that has entered the hot water supply heat exchanger 42 from the water supply pipe 43 moves from the bottom to the top in the hot water storage tank 32b and takes heat from the high temperature water in the hot water storage tank 32b. Naturally, the upper part becomes hot and the lower part becomes cold.

In the main refrigerant circuit 10, a high-pressure side pressure detection device 51 and a discharge temperature thermistor 52 are provided in a pipe 16 on the discharge side of the high-stage compression rotation element 11b.

The high-pressure side pressure detection device 51 is provided in the main refrigerant circuit 10 from the discharge side of the high-stage side compression rotation element 11b to the upstream side of the first expansion device 14, and the high-pressure refrigerant in the main refrigerant circuit 10 is provided. It is only necessary to be able to detect the pressure of.

Further, the discharge temperature thermistor 52 is also provided in the main refrigerant circuit 10 from the discharge side of the high-stage compression rotation element 11b to the upstream side of the first expansion device 14, and the temperature of the high-pressure refrigerant in the main refrigerant circuit 10 is also provided. Should be detected.

The user-side heat medium circuit 30 is provided with a heat medium inlet temperature thermistor 54 that detects the temperature of the user-side heat medium flowing into the user-side heat exchanger 12.

Further, the control device 60 determines the low-stage compression rotation element 11a and the high-stage compression rotation according to the detection pressure from the high-pressure side pressure detection device 51, the detection temperature of the discharge temperature thermistor 52, and the detection temperature of the heat medium inlet temperature thermistor 54. The operating frequency of the element 11b, the valve opening degree of the first expansion device 14, the valve opening degree of the second expansion device 21, and the transfer amount of the heat medium on the utilization side by the transfer device 31 are controlled.

FIG. 2 is a pressure-enthalpy diagram (Ph diagram) under ideal conditions for the refrigeration cycle apparatus according to the present embodiment.

Points a to e and points A to B in FIG. 2 correspond to points in the refrigeration cycle apparatus shown in FIG.

First, the high-pressure refrigerant (point a) discharged from the high-stage compression rotating element 11b branches from the main refrigerant circuit 10 at the refrigerant branch point (point A) after heat is dissipated by the utilization side heat exchanger 12, and the second The expansion device 21 reduces the pressure to the intermediate pressure to become the intermediate pressure refrigerant (point e), and the intermediate heat exchanger 13 exchanges heat.

The high-pressure refrigerant flowing through the main refrigerant circuit 10 after heat is dissipated by the user-side heat exchanger 12 is cooled by the intermediate-pressure refrigerant (point e) flowing through the bypass refrigerant circuit 20, and the enthalpy is reduced (point b). 1 The pressure is reduced by the expansion device 14.

As a result, the refrigerant enthalpy of the refrigerant (point c) flowing into the heat source side heat exchanger 15 after being depressurized by the first expansion device 14 is also reduced. Since the dryness of the refrigerant (the weight ratio of the gas phase component to the total refrigerant) at the time of flowing into the heat source side heat exchanger 15 decreases and the liquid component of the refrigerant increases, the heat source side heat exchanger 15 evaporates. The refrigerant ratio is increased, the amount of heat absorbed from the outside air is increased, and the heat is returned to the suction side (point d) of the low-stage compression rotating element 11a.

On the other hand, in the heat source side heat exchanger 15, the amount of refrigerant corresponding to the gas phase component that does not contribute to evaporation is bypassed by the bypass refrigerant circuit 20 to become a low-temperature intermediate pressure refrigerant (point e), and the intermediate heat exchanger 13 In a state where the refrigerant enthalpy is increased by being heated by the high-pressure refrigerant flowing through the main refrigerant circuit 10, the refrigerant confluence point B between the low-stage side compression rotation element 11a and the high-stage side compression rotation element 11b is reached.

Therefore, on the suction side (point B) of the high-stage compression rotation element 11b, the refrigerant pressure is higher than that on the suction side (point d) of the low-stage compression rotation element 11a, so that the refrigerant density is high and the low-stage compression rotation Since the refrigerant that has merged with the refrigerant discharged from the element 11a is sucked in and further compressed and discharged by the high-stage compression rotating element 11b, the flow rate of the refrigerant flowing into the heat exchanger 12 on the user side is significantly increased, and the flow rate on the user side is significantly increased. The ability to heat water, which is the heat carrier, is greatly increased.

Hereinafter, a case where the hot water storage tank 32b is used for the heat medium circuit 30 on the user side will be described.

Of the plurality of hot water storage tank temperature thermistors, for example, when the detection temperature of the first hot water storage tank temperature thermistor 55a arranged at the highest position of the hot water storage tank 32b is less than a predetermined value, the high temperature water is insufficient in the hot water storage tank 32b. The control device 60 determines.

Then, the control device 60 operates the low-stage compression rotation element 11a and the high-stage compression rotation element 11b to heat the low-temperature water in the utilization-side heat exchanger 12, and the heat medium outlet temperature which is the heating generation temperature thereof. The transport device 31 is operated so that the detected temperature of the thermistor 53 becomes the target temperature.

As a result, the low-temperature water is derived from the lower part of the hot water storage tank 32b, and the high-temperature water generated by heating in the user-side heat exchanger 12 is introduced into the hot water storage tank 32b from the upper part of the hot water storage tank 32b.

Then, since high-temperature water is gradually stored in the hot water storage tank 32b from the upper part, the detection temperature of the heat medium inlet temperature thermistor 54 gradually rises.

A case where the heating terminal 32a is used for the heat medium circuit 30 on the user side will be described.

The control device 60 operates the low-stage compression rotation element 11a and the high-stage compression rotation element 11b to heat the circulating water with the utilization side heat exchanger 12, and the heat medium outlet temperature which is the temperature difference of the circulating water. The transfer device 31 is operated so that the temperature difference between the detection temperature of the thermistor 53 and the detection temperature of the heat medium inlet temperature thermistor 54 becomes the target temperature difference.

As a result, the high-temperature water generated by the user-side heat exchanger 12 is radiated by the heating terminal 32a and used for heating, and the low-temperature water radiated by the heating terminal 32a is heated again by the user-side heat exchanger 12. To. At this time, the temperature difference between the detection temperature of the heat medium outlet temperature thermistor 53 and the detection temperature of the heat medium inlet temperature thermistor 54 is controlled to be the target temperature difference.

Since the heating load gradually decreases, the heat medium is controlled so that the temperature difference between the detection temperature of the heat medium outlet temperature thermista 53 and the detection temperature of the heat medium inlet temperature thermista 54 becomes the target temperature difference. The detection temperature of the outlet temperature thermistor 53 and the detection temperature of the heat medium inlet temperature thermistor 54 gradually increase.

Hereinafter, using FIG. 3, in the utilization side heat medium circuit 30, when the temperature of the utilization side heat medium flowing into the utilization side heat exchanger 12 rises, that is, the detection temperature of the heat medium inlet temperature thermistor 54 rises. The case will be described below.

In FIG. 3, the solid line is a pressure-enthalpy diagram when the temperature of the heat medium on the user side flowing into the heat exchanger 12 on the user side rises with respect to the broken line.

In FIG. 3, as the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger 12 rises, the inlet temperature (point a) of the refrigerant to the utilization-side heat exchanger 12 increases in the direction of increasing enthalpy (a'. Move to point). Further, the outlet temperature (point A) of the refrigerant from the user-side heat exchanger 12 moves in the direction of increasing enthalpy (point A').

Similarly, the outlet temperature (point B) of the refrigerant from the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 also moves in the direction of increasing enthalpy (point B'). Further, the inlet temperature (point e) of the refrigerant to the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 also moves in the direction of increasing enthalpy (point e').

When the pressure exceeds the critical pressure and moves in the direction of increasing enthalpy, the slope of the isotherm with respect to the pressure also becomes steep.

Therefore, even if the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger 12 rises, in order to suppress a decrease in the COP of the refrigeration cycle apparatus 9, the intermediate heat exchanger 13 has an intermediate heat exchanger. The temperature difference between the outlet temperature of the refrigerant from the bypass refrigerant circuit 20 of 13 (point B') and the inlet temperature of the refrigerant to the bypass refrigerant circuit 20 to the intermediate heat exchanger 13 (point e') should not be as small as possible. In addition, the control device 60 must control the valve opening degree of the second expansion device 21.

Further, even if the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger 12 rises, the utilization-side heat exchanger 12 uses the refrigerant discharged from the high-stage compression rotating element 11b to keep the utilization-side heat medium. The heating capacity should not be reduced as much as possible.

Specifically, the ratio of the amount of refrigerant flowing through the bypass refrigerant circuit 20 to the amount of refrigerant flowing on the main refrigerant circuit 10 side of the intermediate heat exchanger 13 is increased.

That is, the valve opening degree of the second expansion device 21 is increased to circulate the bypass refrigerant circuit 20, the high-stage compression rotation element 11b, and the utilization side heat exchanger 12 with respect to the amount of refrigerant circulating in the main refrigerant circuit 10. Increase the ratio of the amount of refrigerant.

As a result, even when the temperature of the utilization-side heat medium flowing into the utilization-side heat exchanger 12 rises, the high-pressure refrigerant flowing through the main refrigerant circuit 10 and the intermediate-pressure refrigerant flowing through the bypass refrigerant circuit 20 in the intermediate heat exchanger 13 The amount of heat exchange increases.

Therefore, it is possible to suppress a decrease in the enthalpy difference (points a'to A') between the outlet of the refrigerant and the inlet of the refrigerant in the user-side heat exchanger 12.

The difference in enthalpy between the high-pressure refrigerant (point a') discharged from the high-stage compression rotating element 11b and the refrigerant branch point (point A') after heat is dissipated by the utilization-side heat exchanger 12 is the high-stage compression. The enthalpy difference of the high-stage compression rotating element 11b is added to the enthalpy difference between the suction side (point B') of the rotating element 11b and the intermediate pressure refrigerant (e'point) flowing through the bypass refrigerant circuit 20.

Therefore, in order to increase the enthalpy difference (points a'to A') between the refrigerant outlet and the refrigerant inlet in the user-side heat exchanger 12, the enthalpy difference (points a'to A') of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 is increased. B'points to e'points) should be increased.

Further, since the amount of the refrigerant circulating in the bypass refrigerant circuit 20, the high-stage compression rotating element 11b, and the utilization side heat exchanger 12 increases, it is possible to suppress the reduction of the heating capacity in the utilization side heat exchanger 12.

Further, the control device 60 reduces the valve opening degree of the first expansion device 14. As a result, the pressure on the high-pressure side of the refrigerant in the main refrigerant circuit 10 rises, so even if the temperature of the heat medium on the user side flowing into the heat exchanger 12 on the user side rises, the outlet of the refrigerant in the heat exchanger 12 on the user side It is possible to suppress a decrease in the enthalpy difference (points a'to A') between the air and the inlet of the refrigerant.

Further, the control device 60 adjusts the valve opening degree of the first expansion device 14 and the valve opening degree of the second expansion device 21 to bring the temperature detected by the discharge temperature thermistor 52 closer to the target value. The target value of the discharge temperature is a value preset in the control device 60.

As a result, the high-pressure refrigerant and the bypass refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13 are prevented from excessively rising or falling in the discharge temperature for detecting the temperature of the refrigerant discharged from the high-stage compression rotating element 11b. It is possible to increase the amount of heat exchange with the intermediate pressure refrigerant flowing through the circuit 20, and increase the amount of the refrigerant circulating in the bypass refrigerant circuit 20, the high-stage compression rotating element 11b, and the utilization side heat exchanger 12.

Further, the control device 60 adjusts the valve opening degree of the first expansion device 14 and the valve opening degree of the second expansion device 21 so that the pressure value detected by the high pressure side pressure detecting device 51 approaches the target value. ing.

This prevents the pressure of the refrigerant discharged from the high-stage compression rotating element 11b from rising or falling excessively, and is used even if the temperature of the heat medium on the user side flowing into the heat exchanger 12 on the user side rises. It is possible to suppress a decrease in the enthalpy difference (points a'to A') between the outlet of the refrigerant and the inlet of the refrigerant in the side heat exchanger 12.

The low-stage compression rotation element 11a and the high-stage compression rotation element 11b are not separated and may be a single compression rotation element. In the case of a single compression rotation element, the bypass refrigerant circuit 20 The refrigerant from is in the process of compressing the compression rotating element.

Further, by using water or antifreeze as the heat medium on the user side, it is possible to use it in the heating terminal 32a or store high temperature water in the hot water storage tank 32b.

As described above, the heat pump system in which the high-pressure side according to the present invention operates at a supercritical pressure can control the COP by performing appropriate control even if the temperature of the heat medium on the user side flowing into the heat exchanger on the user side rises. Since it suppresses the decrease, it is useful for refrigeration, air conditioning, hot water supply, heat pump systems for heating equipment, and the like.

9 Refrigerant cycle device 10 Main refrigerant circuit 11 Compression mechanism 11a Low-stage compression rotation element 11b High-stage compression rotation element 12 Utilization side heat exchanger 13 Intermediate heat exchanger 14 First expansion device 15 Heat source side heat exchanger 16 Piping 20 Bypass refrigerant circuit 21 2nd expansion device 30 User side heat medium circuit 31 Conveyor device 32a Heating terminal 32b Hot water storage tank 33 Heat medium piping 34 1st switching valve 35 2nd switching valve 41 Hot water tap 42 Hot water supply heat exchanger 43 Water supply piping 51 High-pressure side pressure detector 52 Discharge temperature thermistor 54 Heat medium inlet temperature thermistor 55a 1st hot water storage tank temperature thermistor 55b 2nd hot water storage tank temperature thermistor 55c 3rd hot water storage tank temperature thermistor 60 Control device

Claims (7)

A compression mechanism composed of a compression rotation element, a utilization side heat exchanger that heats a utilization side heat medium with a refrigerant discharged from the compression rotation element and exceeding a critical pressure, an intermediate heat exchanger, a first expansion device, and heat source side heat. A main refrigerant circuit formed by connecting exchangers in sequence with pipes,
The refrigerant branched from the pipe between the utilization side heat exchanger and the first expansion device, and after the branched refrigerant is decompressed by the second expansion device, flows through the main refrigerant circuit in the intermediate heat exchanger. A bypass refrigerant circuit that exchanges heat with and joins the refrigerant in the process of compression of the compression rotating element.
Control device and
With
The control device is
When the temperature of the user-side heat medium flowing into the user-side heat exchanger rises,
At least by controlling the valve opening of the second expansion device,
A heat pump system comprising increasing the ratio of the amount of the refrigerant flowing through the bypass refrigerant circuit to the amount of the refrigerant flowing through the main refrigerant circuit side of the intermediate heat exchanger. A heat medium inlet temperature thermister for detecting the temperature of the user-side heat medium flowing into the user-side heat exchanger is provided, and when the detected temperature of the heat medium inlet temperature thermister rises, the control device expands to the second expansion. The heat pump system according to claim 1, wherein the valve opening degree of the apparatus is increased. The heat pump system according to claim 2, wherein the control device reduces the valve opening degree of the first expansion device. A discharge temperature thermistor for detecting the temperature of the refrigerant discharged from the compression rotation element is provided, and the control device adjusts the valve opening degree of the first expansion device and the valve opening degree of the second expansion device. The heat pump system according to claim 3, wherein the temperature detected by the discharge temperature thermistor is brought close to a target value. A high-pressure side pressure detecting device for detecting the pressure of the refrigerant discharged from the compression rotating element is provided, and the control device adjusts the valve opening degree of the first expansion device and the valve opening degree of the second expansion device. The heat pump system according to claim 3, wherein the pressure value detected by the high-pressure side pressure detecting device is brought close to a target value. The heat pump system according to any one of claims 1 to 5, wherein the heat pump system includes a transfer device and includes a user-side heat medium circuit that circulates the user-side heat medium by the transfer device. The heat pump system according to any one of claims 1 to 6, wherein the heat medium on the user side is water or antifreeze.

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