JP2020115068A - Refrigeration cycle device and liquid heating device including the same - Google Patents

Abstract

To provide a refrigeration cycle device and a liquid heating device including the refrigeration cycle device that prevent deterioration of COP by performing appropriate control even when a high pressure is increased.SOLUTION: A refrigeration cycle device includes: a main refrigerant circuit 10 formed by sequentially connecting a compression mechanism 11, a use side heat exchanger 12, an intermediate heat exchanger 13, a first expansion device 14 and a heat source side heat exchanger 15 by using piping 16; a bypass refrigerant circuit 20 that is branched from the piping 16 from the use side heat exchanger 12 to the first expansion device 14 and in which after decompression is performed by a second expansion device 21, heat exchange with a refrigerant flowing in the main refrigerant circuit 10 is performed by the intermediate heat exchanger 13 and joining with a refrigerant of a compression rotating element in the process of being compressed is performed; and a control device 60. The control device 60 controls a valve opening of the second expansion device 21 so that a pressure of the refrigerant after decompressed by the second expansion device 21 maintains a state of exceeding a critical pressure.SELECTED DRAWING: Figure 4

Description

The present invention relates to a refrigeration cycle device and a liquid heating device including the same.

Conventionally, in this type of refrigeration cycle device, a two-stage compressor for compressing the refrigerant in two stages, and a supercritical vapor compression refrigeration cycle including two expansion devices for expanding the refrigerant in two stages are disclosed, Some refrigerants use carbon dioxide (see, for example, Patent Document 1).

The supercritical vapor compression refrigeration cycle of Patent Document 1 includes a gas-liquid separator, and the refrigerant whose main component is a gas phase in the gas-liquid separator is in the middle of an intermediate connection circuit of the two-stage compressor from the injection circuit. It is subjected to intermediate injection into a certain refrigerant mixer, mixed with the refrigerant discharged from the low stage side rotary compression rotary element, and drawn into the high stage side rotary compression rotary element.

In Patent Document 1, the ratio of the excluded volume of the high-stage rotary compression rotary element to the excluded volume of the low-stage rotary compression rotary element (excluded volume ratio), the suction pressure of the two-stage compressor, the refrigerant saturation in the first expansion device The discharge pressure of the low-stage rotary compression rotary element is set to be equal to or lower than the critical pressure of the refrigerant by setting the isentropic exponent root of the quotient divided by the hydraulic pressure or more.

Further, conventionally, a refrigeration cycle apparatus of this type includes a two-stage compressor that compresses the refrigerant in two stages and two expansion devices that expand the refrigerant in two stages even if the refrigerant is not carbon dioxide. There is one (for example, refer to Patent Document 2).

The refrigeration apparatus of Patent Document 2 includes a subcooling heat exchanger, expands a part of the refrigerant discharged from the two-stage compressor, and after exchanging heat with the refrigerant discharged in the subcooling heat exchanger, An injection circuit for injecting into the intermediate port of the compressor is provided, and the opening degree of the expansion valve is controlled by setting the target superheat degree according to the superheat degree at the outlet of the supercooling heat exchanger.

JP, 2010-071643, A JP, 2010-054194, A

However, in the conventional configuration according to Patent Document 1, when the high pressure is increased to generate high temperature water in the supercritical vapor compression refrigeration cycle, the intermediate pressure of the refrigerant in the injection circuit is equal to or lower than the critical pressure of the refrigerant. Therefore, there is a problem that the differential pressure between the high pressure and the intermediate pressure becomes large, and the COP of the supercritical vapor compression refrigeration cycle decreases.

Further, in the conventional configuration according to Patent Document 2, since the control is performed based on the superheat degree at the outlet of the subcooling heat exchanger, when the pressure of the refrigerant discharged from the two-stage compressor and expanded is equal to or higher than the critical pressure. Will be out of control.

An object of the present invention is to solve the above-mentioned problems, and to provide a refrigeration cycle apparatus and a liquid heating apparatus including the same, which do not reduce the COP by performing appropriate control even when the high pressure is increased. To do.

In order to solve the above-mentioned conventional problems, a refrigeration cycle apparatus of the present invention includes a compression mechanism including a compression rotary element, and a use side heat exchanger that heats a use side heat medium with a refrigerant discharged from the compression rotary element. A main refrigerant circuit formed by sequentially connecting an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger by piping, and from the piping between the use side heat exchanger and the first expansion device A bypass refrigerant circuit that is branched and is decompressed by the second expansion device, and then heat-exchanges with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger, and joins with the refrigerant in the middle of compression of the compression rotary element; A temperature difference between an outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and an inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, the refrigerant is the intermediate heat exchange. Larger than the case of flowing in a gas-liquid two-phase state through the reactor, and between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger The control is performed such that the temperature difference is larger than the temperature difference between the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the outlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger. The device controls the valve opening of the second expansion device so that the pressure of the refrigerant after being decompressed by the second expansion device remains in a state of exceeding a critical pressure. Is.

Thereby, even when the pressure of the refrigerant after being decompressed by the second expansion device exceeds the critical pressure, a large enthalpy difference between the refrigerant outlet and the refrigerant inlet of the intermediate heat exchanger of the bypass refrigerant circuit is taken. In addition, since the flow rate of the refrigerant flowing through the intermediate heat exchanger of the bypass refrigerant circuit can be increased, it is possible to provide a refrigeration cycle apparatus that realizes a high COP.

According to the present invention, it is possible to provide a refrigeration cycle apparatus that does not reduce COP by performing appropriate control even when the high pressure is increased, and a liquid heating apparatus including the same.

1 is a configuration diagram of a liquid heating device according to Embodiment 1 of the present invention (A) Pressure-enthalpy diagram (Ph diagram) when intermediate pressure of the refrigeration cycle device in Embodiment 1 of the present invention is lower than critical pressure (b) Intermediate pressure of the same refrigeration cycle device is lower than critical pressure High pressure-enthalpy diagram (Ph diagram) The figure which shows the relationship between the temperature of the refrigerant of the main refrigerant corridor which flows through the intermediate heat exchanger of the refrigerating cycle device in Embodiment 1 of this invention, and the refrigerant of a bypass refrigerant circuit. (A) The figure which shows the relationship between (DELTA)TM in Embodiment 1 of this invention, and the refrigerant|coolant circulation amount of the bypass refrigerant circuit which flows through an intermediate heat exchanger (b) The heat exchange amount of the same intermediate heat exchanger, and intermediate heat exchange (C) shows the relationship between the refrigerant circulation amount of the bypass refrigerant circuit flowing through the heat exchanger and the temperature difference ΔT between ΔTH and ΔTL and the refrigerant circulation amount of the bypass refrigerant circuit flowing through the intermediate heat exchanger. Figure In the liquid heating device according to Embodiment 1 of the present invention, the pressure-enthalpy diagram (Ph diagram) of the refrigeration cycle device when the inlet temperature of the heat utilization medium of the utilization side heat exchanger changes.

A first aspect of the present invention is a compression mechanism including a compression rotary element, a use side heat exchanger that heats a use side heat medium by a refrigerant discharged from the compression rotary element, an intermediate heat exchanger, a first expansion device, and a heat source. After branching from the main refrigerant circuit formed by sequentially connecting side heat exchangers with piping and the piping between the utilization side heat exchanger and the first expansion device, and after decompressing with the second expansion device , A bypass refrigerant circuit that is heat-exchanged with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger, and is joined to the refrigerant in the middle of compression of the compression rotary element, and a control device, and the intermediate heat exchanger The temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, than when the refrigerant flows through the intermediate heat exchanger in a gas-liquid two-phase state Is also large, and the temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger, the bypass of the intermediate heat exchanger. The control device controls the valve opening degree of the second expansion device so that the temperature difference between the refrigerant inlet temperature of the refrigerant circuit and the refrigerant outlet temperature of the main refrigerant circuit of the intermediate heat exchanger is larger than the temperature difference. Is controlled so that the pressure of the refrigerant after being decompressed by the second expansion device is maintained in a state of exceeding the critical pressure.

Thereby, even when the pressure of the refrigerant after being decompressed by the second expansion device exceeds the critical pressure, a large enthalpy difference between the refrigerant outlet and the refrigerant inlet of the intermediate heat exchanger of the bypass refrigerant circuit is taken. In addition, since the flow rate of the refrigerant flowing through the intermediate heat exchanger of the bypass refrigerant circuit can be increased, it is possible to provide a refrigeration cycle apparatus that realizes a high COP.

A second aspect of the present invention is, in particular, in the first aspect, the higher the pressure of the refrigerant after being decompressed by the second expansion device, the higher the outlet temperature of the refrigerant and the refrigerant outlet temperature of the bypass refrigerant circuit of the intermediate heat exchanger. The control device controls the valve opening degree of the second expansion device so that the temperature difference from the inlet temperature becomes large.

Thereby, the inlet temperature of the use side heat medium to the use side heat exchanger, the outlet temperature of the use side heat medium from the use side heat exchanger, and the heat source side heat medium (air) to the heat source side heat exchanger. Rises, the pressure of the intermediate heat exchanger of the bypass refrigerant circuit also rises. However, in order to secure a necessary enthalpy difference at that time, as the pressure of the refrigerant after being decompressed by the second expansion device becomes higher, The control device controls the valve opening degree of the second expansion device so that the temperature difference between the outlet temperature of the refrigerant and the inlet temperature of the refrigerant of the intermediate heat exchanger of the bypass refrigerant circuit becomes large. Even if the temperature rises, it is possible to secure the enthalpy difference between the outlet and the inlet of the refrigerant of the intermediate heat exchanger of the bypass refrigerant circuit, so that it is possible to provide a refrigeration cycle apparatus that realizes a high COP.

In a third aspect of the invention, in particular, in the first or second aspect of the invention, the control device is characterized in that the pressure value of the refrigerant discharged from the compression mechanism, the outlet temperature of the refrigerant of the utilization side heat exchanger, and the intermediate heat. From the inlet temperature of the refrigerant of the bypass refrigerant circuit of the exchanger, it is determined whether or not the pressure of the refrigerant after being decompressed by the second expansion device is equal to or higher than a critical pressure. ..

With this, it is possible to determine whether the pressure of the refrigerant after being decompressed by the second expansion device is equal to or higher than the critical pressure without providing a pressure detection device, and thus a refrigeration cycle device that realizes cost reduction can be obtained. Can be provided.

A fourth invention is characterized in that, in any one of the first to third inventions, the refrigerant is carbon dioxide.

According to this, in the usage-side heat exchanger, the temperature of the usage-side heat medium can be raised when the usage-side heat medium is heated by the refrigerant.

A fifth invention particularly uses the refrigeration cycle of any one of the first to fourth inventions, and is provided with a utilization-side heat medium circuit for circulating the utilization-side heat medium by a carrier device. It is a heating device.

According to this, it is possible to provide a liquid heating device that can use the high-temperature use-side heat medium without lowering the COP of the refrigeration cycle device.

In a sixth aspect of the present invention, in particular, in the fifth aspect, a heat medium outlet temperature thermistor for detecting the temperature of the use side heat medium flowing out from the use side heat exchanger, and an inflow into the use side heat exchanger. A heat medium inlet temperature thermistor for detecting the temperature of the utilization side heat medium, and the control device operates the carrier device so that the detected temperature of the heat medium outlet temperature thermistor becomes a target temperature. When the detected temperature of the heat medium inlet temperature thermistor exceeds a first predetermined temperature, the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the bypass refrigerant circuit of the intermediate heat exchanger. The temperature difference from the inlet temperature of the refrigerant is larger than when the refrigerant flows through the intermediate heat exchanger in a gas-liquid two-phase state, and the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger. , A temperature difference between the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger, the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, and the main refrigerant circuit of the intermediate heat exchanger The control device controls the valve opening degree of the second expansion device so that the temperature difference is larger than the temperature difference from the outlet temperature of the refrigerant.

This makes it possible to provide, for example, a liquid heating device that can store high-temperature water in a hot water storage tank without lowering COP even when the high pressure of the refrigeration cycle device is increased.

A seventh aspect of the invention is, in particular, in the fifth aspect, a heat medium outlet temperature thermistor for detecting the temperature of the utilization side heat medium flowing out from the utilization side heat exchanger, and a heat medium outlet temperature thermistor flowing into the utilization side heat exchanger. A heat medium inlet temperature thermistor for detecting the temperature of the utilization side heat medium, wherein the control device has a temperature difference between the temperature detected by the heat medium outlet temperature thermistor and the temperature detected by the heat medium inlet temperature thermistor. When the transfer device is operated so as to achieve the target temperature difference, and when the detected temperature of the heat medium outlet temperature thermistor exceeds a second predetermined temperature, the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger is The temperature difference between the outlet temperature and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger is greater than when the refrigerant flows through the intermediate heat exchanger in a gas-liquid two-phase state, and The temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger is a refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger. The control device controls the valve opening degree of the second expansion device so that the temperature difference between the inlet temperature of the second heat exchanger and the outlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger is larger than the temperature difference. It is characterized by that.

This makes it possible to provide a liquid heating device that heats using, for example, high-temperature water without lowering the COP even when the high pressure of the refrigeration cycle device is increased.

In an eighth aspect of the present invention, in any one of the fifth to seventh aspects, the control device controls the pressure value of the refrigerant discharged from the compression mechanism and the utilization-side heat flowing into the utilization-side heat exchanger. From the temperature of the medium and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, it is determined whether the pressure of the refrigerant after being decompressed by the second expansion device is equal to or higher than a critical pressure. It is characterized by that.

With this, it is possible to determine whether the pressure of the refrigerant after being decompressed by the second expansion device is equal to or higher than the critical pressure without providing a pressure detection device, and thus a refrigeration cycle device that realizes cost reduction can be obtained. Can be provided.

A ninth invention is characterized in that, in any one of the fifth to eighth inventions, the use side heat medium is water or an antifreeze liquid.

With this, for example, it is possible to store high-temperature water in the hot water storage tank without lowering the COP, and to provide a liquid heating device that heats using the high-temperature water.

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to this embodiment.

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

The main refrigerant circuit 10 includes a compression mechanism 11 for compressing a refrigerant, a utilization side heat exchanger 12 which is a radiator, an intermediate heat exchanger 13, a first expansion device 14, and a heat source side heat exchanger 15 which is an evaporator. 16 are sequentially connected and formed, and carbon dioxide (CO ₂ ) is used as a refrigerant.

Although carbon dioxide is optimally used as the refrigerant, a non-azeotropic mixed refrigerant such as R407C, a pseudo-azeotropic mixed refrigerant such as R410A, or a single refrigerant such as R32 can also be used.

The compression mechanism 11 includes a low-stage compression rotary element 11a and a high-stage compression rotary element 11b. The usage-side heat exchanger 12 heats the usage-side heat medium by the refrigerant discharged from the high-stage compression rotation element 11b.

In addition, the volume ratio of the low-stage compression rotary element 11a and the high-stage compression rotary element 11b constituting the compression mechanism 11 is constant, and the drive shaft (not shown) is made common and arranged in one container. It consists of one compressor.

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

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

Further, the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b may be a two-stage compression mechanism 11 configured by two independent compressors.

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

A second expansion device 21 is provided in the bypass refrigerant circuit 20. After a part of the high-pressure refrigerant after passing through the use-side heat exchanger 12 or a 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 joins the refrigerant between the low-stage compression rotary element 11a and the high-stage compression rotary element 11b.

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

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

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

The high-temperature water generated in the usage-side heat exchanger 12 is introduced into the hot-water storage tank 32b from the upper part of the hot-water storage tank 32b, the low-temperature water is drawn out from the lower part of the hot-water storage tank 32b, and is heated in the usage-side heat exchanger 12. It

The hot water supply heat exchanger 42 is arranged in the hot water storage tank 32b, and exchanges heat 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 tap 41 is opened, water is supplied from the water supply pipe 43 into the hot water heat exchanger 42, heated by the hot water heat exchanger 42, and adjusted to a predetermined temperature by the hot water tap 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 heatings that are not mixed with each other. ..

The hot water supply heat exchanger 42 is a water heat exchanger that uses a copper tube or a stainless steel tube as a heat transfer tube, 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. Are connected. The water supply pipe 43 puts water at room temperature at the lower end of the hot water supply heat exchanger 42, that is, below the hot water storage tank 32b.

The room-temperature water that has entered the hot water supply heat exchanger 42 through the water supply pipe 43 removes heat from the high-temperature water in the hot-water storage tank 32b while moving from the lower part to the upper part in the hot-water storage tank 32b, and becomes the heated hot water. Then, hot water is supplied from the hot water tap 41.

In order to measure the temperature of hot water at a plurality of different height positions, 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 are provided in the hot water storage tank 32b. It is provided.

The room temperature water that has entered the hot water supply heat exchanger 42 through the water supply pipe 43 removes heat from the high temperature water in the hot water storage tank 32b while moving from the lower side to the upper side in the hot water storage tank 32b. Is naturally high in the upper part and low in the lower part.

In the main refrigerant circuit 10, a high pressure side pressure detection device 51 is provided in the discharge side pipe 16 of the high stage side compression rotary 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 compression rotary element 11b to the upstream side of the first expansion device 14, and the high-pressure refrigerant of the main refrigerant circuit 10 is provided. It is only necessary to be able to detect the pressure of.

Further, in the downstream side of the utilization side heat exchanger 12 of the main refrigerant circuit 10 and in the upstream side of the intermediate heat exchanger 13, an intermediate heat exchange for detecting the temperature of the refrigerant flowing out from the utilization side heat exchanger 12 is provided. Is provided with a main refrigerant inlet thermistor, and the intermediate heat exchanger main refrigerant outlet thermistor is provided in the pipe 16 on the downstream side of the intermediate heat exchanger 13 of the main refrigerant circuit 10 and on the upstream side of the first expansion device 14. 58 is provided.

The bypass refrigerant circuit 20 is provided with an intermediate heat exchanger bypass inlet thermistor 56 on the downstream side of the second expansion device 21 and on the upstream side of the intermediate heat exchanger 13. Further, an intermediate heat exchanger bypass outlet thermistor 52 is provided on the downstream side of the intermediate heat exchanger 13.

In the use side heat medium circuit 30, a heat medium outlet temperature thermistor 53 for detecting the temperature of the use side heat medium flowing out from the use side heat exchanger 12, and a use side heat medium flowing into the use side heat exchanger 12. And a heat medium inlet temperature thermistor 54 for detecting the temperature of the.

Further, the control device 60 controls the detected pressure from the high pressure side pressure detection device 51, the calculated intermediate pressure, and the temperature difference between the detected temperature of the intermediate heat exchanger bypass outlet thermistor 52 and the detected temperature of the intermediate heat exchanger bypass inlet thermistor 56. (ΔTM), temperature difference between the temperature detected by the intermediate heat exchanger bypass outlet thermistor 52 and the temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57 (ΔTH), the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56, and the intermediate heat Depending on the temperature difference (ΔTL) from the temperature detected by the exchanger main refrigerant outlet thermistor 58, the temperature detected by the heat medium outlet temperature thermistor 53, and the temperature detected by the heat medium inlet temperature thermistor 54, the low-stage compression rotary element 11a and the high-stage side The operating frequency of the compression rotating element 11b, the valve opening degrees of the first expansion device 14 and the second expansion device 21, and the amount of the use-side heat medium carried by the carrier device 31 are controlled.

A method for the control device 60 to calculate the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 in the bypass refrigerant circuit 20 will be described later.

FIG. 2 is a pressure-enthalpy diagram (Ph diagram) under ideal conditions for the refrigeration cycle apparatus according to the present embodiment. FIG. 2(a) shows that the high pressure is less than a predetermined pressure, and FIG. Indicates the case where the high pressure is equal to or higher than a predetermined pressure.

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 rotary element 11 b radiates heat in the usage-side heat exchanger 12 and then branches from the main refrigerant circuit 10 at the refrigerant branch point A, and is then discharged by the second expansion device 21. The pressure is reduced to an intermediate pressure to become an intermediate pressure refrigerant (point e), and heat is exchanged in the intermediate heat exchanger 13.

The high-pressure refrigerant flowing in the main refrigerant circuit 10 after radiating heat in the usage-side heat exchanger 12 is cooled by the intermediate-pressure refrigerant (point e) flowing in the bypass refrigerant circuit 20, and is in a state where the enthalpy is reduced (point b). 1. The pressure is reduced by the expansion device 14.

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

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

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

When the discharge pressure of the high-stage compression rotary element 11b rises and exceeds the predetermined value, the control device 60 causes the refrigerant pressure after being decompressed by the second expansion device 21 to exceed the critical pressure. Therefore, the control of the valve opening degree of the second expansion device 21 is started.

Specifically, when the control device 60 determines that the detected pressure of the high-pressure side pressure detection device 51 has risen and exceeds the first predetermined high pressure value, and the intermediate pressure is equal to or lower than the critical pressure, the intermediate pressure is The operation of the second expansion device 21 is started in the direction in which the valve opening becomes larger so that the critical pressure is exceeded.

Then, as shown in FIG. 2B, the control device 60 operates in the direction in which the valve opening degree of the second expansion device 21 increases, and the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11a. The operating frequency of 11b is increased to increase the circulation amount of the refrigerant flowing between the utilization side heat exchanger 12 and the bypass refrigerant circuit 20, and the detected pressure from the high pressure side pressure detection device 51 is the target high pressure value. 2 Set to a predetermined high pressure value. The second predetermined high voltage value is a value higher than the first predetermined high voltage value.

That is, since the flow rate of the refrigerant flowing through the bypass refrigerant circuit 20 can be increased by increasing the valve opening degree of the second expansion device 21, the suction pressure of the high-stage compression rotary element 11b is set to the critical pressure that is a predetermined intermediate pressure value. Can be kept above. As a result, the suction pressure of the high-stage compression rotary element 11b, that is, the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21, is maintained in a state of exceeding the critical pressure that is a predetermined intermediate pressure value. In addition to this, the heating capacity of the refrigerant in the utilization side heat exchanger 12 can be increased.

The low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b may have a configuration of the compression mechanism 11 including two independent compressors, at least the high-stage side compression rotary element. The operating frequency of 11b may be increased.

Here, a method in which the control device 60 calculates the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 in the bypass refrigerant circuit 20 will be described.

The control device 60 stores a pressure-enthalpy diagram (Ph diagram) as shown in FIG.

Then, the high-pressure side pressure detection device 51 measures the high-pressure side pressure (the discharge pressure of the high-stage compression rotary element 11b), and the intermediate heat exchanger main refrigerant inlet thermistor 57 measures the refrigerant outlet temperature of the use-side heat exchanger 12 (point A). The intermediate heat exchanger bypass inlet thermistor 56 detects the inlet temperature (point e) of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 every predetermined time.

Then, the control device 60 calculates the pressure and the enthalpy at the point e based on the ideal condition that the enthalpies at the points A and e are substantially the same value, and the pressure is reduced by the second expansion device 21. It is possible to calculate the value of the pressure (intermediate pressure) of the refrigerant after cooling and to judge whether or not the value is equal to or higher than the critical pressure.

The temperature detected by the heat medium inlet temperature thermistor 54 may be used instead of the temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57, as the values are substantially the same.

That is, the discharge pressure of the high-stage compression rotary element 11b, the outlet temperature of the refrigerant of the utilization side heat exchanger 12 (point A), and the inlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 (point e). Alternatively, it is determined from the temperature of the use side heat medium flowing into the use side heat exchanger 12 that the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is equal to or higher than the critical pressure. You can do it.

This makes it possible to determine whether the pressure (intermediate pressure) of the refrigerant that has been decompressed by the second expansion device 21 remains in a state of exceeding the critical pressure.

In the present embodiment, the suction pressure of the high-stage compression rotary element 11b, that is, the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is maintained in a state of exceeding the critical pressure, and the intermediate heat The control device 60 controls the valve opening degree of the second expansion device 21 so that the amount of heat exchange between the refrigerant in the bypass refrigerant circuit 20 and the refrigerant in the main refrigerant circuit 10 in the exchanger 13 is maximized.

The reason is that when the amount of heat exchange in the intermediate heat exchanger 13 is the maximum, the enthalpy at point b in FIG. 2B is reduced. This is because the enthalpy at the point c is also reduced, and the dryness of the refrigerant in the heat source side heat exchanger 15 is reduced, and the amount of heat absorption is increased, whereby the COP can be maximized.

The specific control method will be described below. FIG. 3 is a diagram showing the relationship between the refrigerant in the main refrigerant circuit 10 flowing through the intermediate heat exchanger 13 and the temperature of the refrigerant in the bypass refrigerant circuit 20.

In FIG. 3, the temperature difference (ΔTM) between the detected temperature (point B) of the intermediate heat exchanger bypass outlet thermistor 52 and the detected temperature (e) of the intermediate heat exchanger bypass inlet thermistor 56, the intermediate heat exchanger bypass outlet thermistor 52. Difference (ΔTH) between the detected temperature (point B) and the detected temperature (point A) of the intermediate heat exchanger main refrigerant inlet thermistor 57, the detected temperature (e) of the intermediate heat exchanger bypass inlet thermistor 56 and the intermediate heat exchange The controller 60 controls the valve opening of the second expansion device 21 based on the temperature difference (ΔTL) from the detected temperature (b) of the main refrigerant outlet thermistor 58.

Here, FIG. 4A is a diagram showing the relationship between ΔTM and the refrigerant circulation amount of the bypass refrigerant circuit 20 flowing through the intermediate heat exchanger 13. FIG. 4B is a diagram showing the relationship between the heat exchange amount of the intermediate heat exchanger 13 and the refrigerant circulation amount of the bypass refrigerant circuit 20 flowing through the intermediate heat exchanger 13. FIG. 4C is a diagram showing the relationship between ΔTH and ΔTL and the refrigerant circulation amount of the bypass refrigerant circuit 20 flowing through the intermediate heat exchanger 13.

First, in FIG. 4A, the solid line shows the change when the intermediate pressure is supercritical, and the broken line shows the case where the intermediate pressure is in the gas-liquid two-phase region.

When the bypass refrigerant circulation amount flowing in the bypass refrigerant circuit 20 is small, the refrigerant circulation amount in the main refrigerant circuit 10 is larger than the bypass refrigerant circulation amount flowing in the bypass refrigerant circuit 20, so that the refrigerant flowing in the bypass refrigerant circuit 20 is sufficient. When heated, the outlet temperature (point B) of the refrigerant in the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 easily rises, and ΔTM increases.

On the other hand, as the bypass refrigerant circulation amount increases, the difference in flow rate between the bypass refrigerant circulation amount flowing in the bypass refrigerant circuit 20 and the refrigerant circulation amount in the main refrigerant circuit 10 becomes smaller, so that the bypass refrigerant circuit of the intermediate heat exchanger 13 The temperature rise of the outlet temperature (point B) of the refrigerant of 20 is suppressed and ΔTM becomes small.

That is, when the intermediate pressure is in the gas-liquid two-phase region, when the bypass refrigerant circulation amount exceeds a certain amount, the liquid component occupying the refrigerant increases and is obtained by heat exchange with the refrigerant circulating in the main refrigerant circuit 10. Since the heat becomes latent heat and the temperature of the refrigerant flowing through the bypass refrigerant circuit 20 does not rise, ΔTM becomes substantially zero. On the other hand, when the intermediate pressure exceeds the critical pressure, the temperature of the refrigerant rises because there is no liquid component, and ΔTM does not become substantially zero.

Next, in FIG. 4B, the solid line shows the change when the intermediate pressure is supercritical, and the broken line shows the case where the intermediate pressure is in the gas-liquid two-phase region.

The amount of heat exchange of the intermediate heat exchanger 13 is the magnitude of ΔTM that maximizes the amount of heat exchange of the intermediate heat exchanger 13 when the intermediate pressure is in the gas-liquid two-phase region and when it exceeds the critical pressure. However, when the critical pressure is exceeded, ΔTM has a larger value than in the case of the gas-liquid two-phase region.

Next, in FIG. 4C, the inlet temperature (point A) of the refrigerant of the intermediate heat exchanger 13 of the main refrigerant circuit 10 is constant at the inlet temperature of the use side heat medium to the use side heat exchanger 12. , Suppose there is no temperature change.

At this time, if the valve opening degree of the second expansion device 21 is small, and the bypass refrigerant circulation amount flowing through the bypass refrigerant circuit 20 is small, the refrigerant of the main refrigerant circuit 10 with respect to the bypass refrigerant circulation amount flowing through the bypass refrigerant circuit 20. Since the circulation amount is large, the refrigerant flowing in the bypass refrigerant circuit 20 is sufficiently heated, and the outlet temperature (point B) of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 is the intermediate heat exchanger 13 of the main refrigerant circuit 10. The temperature difference ΔTH, which is the temperature difference, is small because it is close to the refrigerant inlet temperature (point A).

On the other hand, the outlet temperature (point e) of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 is the temperature of the refrigerant after being decompressed by the second expansion device 21, and the valve opening degree of the second expansion device 21 is Is small and the amount of bypass refrigerant in the bypass refrigerant circuit 20 is small, the intermediate pressure is also low, so the temperature of the refrigerant is low. Therefore, the temperature difference ΔTL from the outlet temperature (point b) of the main refrigerant circuit 10 of the intermediate heat exchanger 13 becomes large.

However, when the control device 60 operates the valve opening degree of the second expansion device 21 in the direction of increasing the bypass refrigerant circulation amount, the heat exchange amount of the intermediate heat exchanger 13 increases, so that the intermediate heat exchanger is increased. The temperature rise of the refrigerant outlet temperature (point B) of the bypass refrigerant circuit 20 of 13 is suppressed, and ΔTH increases.

Furthermore, as the control device 60 operates the valve opening degree of the second expansion device 21 in a direction to increase and increases the bypass refrigerant circulation amount, the intermediate pressure increases, so the bypass refrigerant circuit of the intermediate heat exchanger 13 is generated. The temperature of the refrigerant outlet temperature of 20 (point e) rises, and ΔTL, which is the temperature difference from the outlet temperature (point b) of the main refrigerant circuit 10 of the intermediate heat exchanger 13, decreases.

Then, in the present embodiment, control device 60 executes the intermediate pressure supercritical operation mode described below.

(Intermediate pressure supercritical operation mode)
When the control device 60 determines that the pressure detected by the high-pressure side pressure detection device 51 has risen and exceeds the first predetermined high pressure value, and the intermediate pressure is below the critical pressure, the intermediate pressure exceeds the critical pressure. State in which the second expansion device 21 starts to operate in the direction in which the valve opening increases, and the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 exceeds the critical pressure. So that the refrigerant flows through the intermediate heat exchanger 13 in a gas-liquid two-phase state, the outlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 and the bypass refrigerant of the intermediate heat exchanger 13 The control device 60 controls the valve opening degree of the second expansion device 21 so that the temperature difference (ΔTM) from the refrigerant inlet temperature of the circuit 20 becomes a large value.

That is, the refrigerant flows through the intermediate heat exchanger 13 in a gas-liquid two-phase state so that the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 remains in a state exceeding the critical pressure. Also, the controller 60 controls the temperature difference (ΔTM) between the detected temperature (point B) of the intermediate heat exchanger bypass outlet thermistor 52 and the detected temperature (e) of the intermediate heat exchanger bypass inlet thermistor 56 to be a large value. Controls the valve opening of the second expansion device 21.

At the same time, in the present embodiment, when the control device 60 determines that the pressure detected by the high pressure side pressure detection device 51 has risen and exceeds the first predetermined high pressure value, if the intermediate pressure is below the critical pressure, , So that the intermediate pressure exceeds the critical pressure, the second expansion device 21 is started to operate in the direction in which the valve opening increases, and the pressure of the refrigerant after being decompressed by the second expansion device 21 (intermediate Pressure) exceeds the critical pressure so that the refrigerant outlet temperature of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 is higher than that of the refrigerant flowing in the intermediate heat exchanger 13 in a gas-liquid two-phase state. The temperature difference (ΔTH) from the inlet temperature of the refrigerant of the main refrigerant circuit 10 of the intermediate heat exchanger 13 is equal to the inlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 and the main refrigerant circuit 10 of the intermediate heat exchanger 13. The control device 60 controls the valve opening degree of the second expansion device 21 so that the temperature difference becomes larger than the temperature difference (ΔTL) from the outlet temperature of the refrigerant.

That is, the refrigerant flows through the intermediate heat exchanger 13 in a gas-liquid two-phase state so that the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 remains in a state exceeding the critical pressure. Also, the temperature difference (ΔTH) between the detected temperature of the intermediate heat exchanger bypass outlet thermistor 52 (point B) and the detected temperature of the intermediate heat exchanger main refrigerant inlet thermistor 57 (point A) is the intermediate heat exchanger bypass inlet thermistor. The control device 60 controls the valve of the second expansion device 21 such that the temperature difference (ΔTL) between the detected temperature (e) of 56 and the detected temperature (b) of the main refrigerant outlet thermistor 58 of the intermediate heat exchanger is greater than that. Control the opening.

While performing the above control, the control device 60, as shown in FIG. 4, the refrigerant outlet temperature of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 and the bypass refrigerant circuit 20 of the intermediate heat exchanger 13. Difference (ΔTM) from the inlet temperature of the refrigerant in the intermediate heat exchanger 13 and the intermediate temperature of the refrigerant in the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 as compared with the case where the refrigerant flows in the intermediate heat exchanger 13 in a gas-liquid two-phase state. Temperature difference (ΔTH) between the inlet temperature of the refrigerant of the main refrigerant circuit 10 of the heat exchanger 13, the inlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13, and the refrigerant of the main refrigerant circuit 10 of the intermediate heat exchanger 13. The valve opening degree of the second expansion device 21 is adjusted so that the temperature difference (ΔT) with the temperature difference (ΔTL) from the outlet temperature of the second expansion device 21 becomes the maximum value. The amount of circulation of the bypass refrigerant flowing through the bypass refrigerant circuit 20 is set.

The relationship between ΔTM, ΔT, and the heat exchange amount of the intermediate heat exchanger 13 is preset in the control device 60, and ΔTM and ΔT are values that maximize the heat exchange amount of the intermediate heat exchanger 13. Therefore, the control device 60 adjusts the valve opening degree of the second expansion device 21 and sets the bypass refrigerant circulation amount flowing through the bypass refrigerant circuit 20.

The above is the control contents of the intermediate pressure supercritical operation mode.

As a result, it is possible to provide a refrigeration cycle device that realizes a high COP.

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

Of the plurality of hot water storage tank temperature thermistors, for example, when the detected 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, there is not enough high temperature water in the hot water storage tank 32b. Then, the control device 60 determines.

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

As a result, the low temperature water is drawn out from the lower part of the hot water storage tank 32b and the high temperature water generated by heating in the use side heat exchanger 12 is introduced into the hot water storage tank 32b from the upper part of the hot water storage tank 32b. At this time, since the temperature detected by the heat medium inlet temperature thermistor 54 is equal to or lower than the first predetermined temperature, the operation is performed in the state shown in FIG.

Then, since hot water is gradually stored in the hot water storage tank 32b from above, the temperature detected by the heat medium inlet temperature thermistor 54 gradually rises, but the temperature detected by the heat medium inlet temperature thermistor 54 is the first predetermined value. When the temperature is exceeded, the device operates in the state shown in FIG.

That is, the second expansion device 21 is operated in a direction in which the valve opening becomes large, and the operating frequencies of the low-stage compression rotary element 11a and the high-stage compression rotary element 11b are increased to increase the use-side heat exchanger 12 The circulation amount of the refrigerant flowing between the bypass refrigerant circuit 20 and the bypass refrigerant circuit 20 is increased so that the detected pressure from the high pressure side pressure detection device 51 becomes the second predetermined high pressure value which is the target high pressure value. At the same time, the intermediate pressure supercritical operation mode is executed.

As a result, the inlet temperature of the heat medium to the use-side heat exchanger 12 becomes high, and the enthalpy difference (a-A) of the refrigerant in the use-side heat exchanger 12 becomes small. By increasing the heating capacity of the refrigerant, the supply of the high temperature water to the hot water storage tank 32b can be maintained.

Then, when the detected temperature of the heat medium inlet temperature thermistor 54 exceeds the third predetermined temperature higher than the first predetermined temperature, the operating frequencies of the low-stage compression rotary element 11a and the high-stage compression rotary element 11b are reduced. Thus, the hot-water storage is performed while suppressing the pressure increase of the high-pressure refrigerant in the usage-side heat exchanger 12 so that the pressure of the high-pressure refrigerant in the usage-side heat exchanger 12 does not exceed the second predetermined high-pressure value that is the target high-pressure value. High temperature water can be stored in the tank 32b.

As the threshold values, instead of the first predetermined temperature and the third predetermined temperature that are the detection temperatures of the heat medium inlet temperature thermistor 54, the first predetermined high pressure value and the second predetermined pressure value that are the detection pressures of the high pressure side pressure detection device 51, respectively. A similar driving operation may be executed using the predetermined high pressure value.

Further, the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b may have a configuration of the compression mechanism 11 configured by two independent compressors, at least the high-stage side compression rotary element. It suffices to reduce the operating frequency of 11b.

A case where the heating terminal 32a is used in the use side heat medium circuit 30 will be described.

The control device 60 operates the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b to heat the circulating water in the use side heat exchanger 12, but 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 temperature detected by the thermistor 53 and the temperature detected by the heat medium inlet temperature thermistor 54 becomes the target temperature difference.

Thereby, the high-temperature water generated in the use-side heat exchanger 12 radiates heat to the heating terminal 32a and is used for heating, and the low-temperature water radiated in the heating terminal 32a is heated again in the use-side heat exchanger 12. It At this time, the temperature difference between the temperature detected by the heat medium outlet temperature thermistor 53 and the temperature detected by the heat medium inlet temperature thermistor 54 is controlled to be the target temperature difference, and the temperature detected by the heat medium outlet temperature thermistor 53 is set to the first temperature. Since the temperature is equal to or lower than the predetermined temperature, the operation is performed in the state shown in FIG.

Since the heating load gradually decreases, the heat medium is controlled so that the temperature difference between the temperature detected by the heat medium outlet temperature thermistor 53 and the temperature detected by the heat medium inlet temperature thermistor 54 becomes the target temperature difference. The detected temperature of the outlet temperature thermistor 53 and the detected temperature of the heat medium inlet temperature thermistor 54 gradually increase, but when the detected temperature of the heat medium outlet temperature thermistor 53 exceeds the second predetermined temperature, the temperature shown in FIG. ).

That is, the second expansion device 21 is operated in a direction in which the valve opening becomes large, and the operating frequencies of the low-stage compression rotary element 11a and the high-stage compression rotary element 11b are increased to increase the use-side heat exchanger 12 The circulation amount of the refrigerant flowing between the bypass refrigerant circuit 20 and the bypass refrigerant circuit 20 is increased so that the detected pressure from the high pressure side pressure detection device 51 becomes the second predetermined high pressure value which is the target high pressure value. At the same time, the intermediate pressure supercritical operation mode is executed.

As a result, the heating load is reduced and the enthalpy difference (a-A) in the usage-side heat exchanger 12 is reduced. By increasing the heating capacity of the refrigerant in the usage-side heat exchanger 12, the high-temperature water is cooled. The supply to the heating terminal 32a can be maintained.

When the detected temperature of the heat medium outlet temperature thermistor 53 exceeds the fourth predetermined temperature higher than the second predetermined temperature, the operating frequencies of the low-stage compression rotary element 11a and the high-stage compression rotary element 11b are reduced. By doing so, the pressure of the high-pressure refrigerant in the usage-side heat exchanger 12 is controlled so as not to exceed the second predetermined high-pressure value that is the target high-pressure value, while suppressing the pressure increase of the high-pressure refrigerant in the usage-side heat exchanger 12, It can be used as a heating device that uses high-temperature water.

As the threshold value, instead of the second predetermined temperature and the fourth predetermined temperature which are the detected temperatures, the first predetermined high pressure value and the second predetermined high pressure value which are the detection pressures of the high pressure side pressure detection device 51 are used, respectively. The same driving operation may be executed.

Hereinafter, referring to FIG. 5, when the hot water storage tank 32b is used in the use side heat medium circuit 30, when the detected temperature of the heat medium inlet temperature thermistor 54 exceeds the first predetermined temperature, or in the use side heat medium circuit 30. In the case of using the heating terminal 32a, the intermediate pressure supercritical operation mode executed by the control device 60 when the detected temperature of the heat medium outlet temperature thermistor 53 exceeds the second predetermined temperature will be described below.

In FIG. 5, a solid line indicates a case where the hot water storage tank 32b is used in the use side heat medium circuit 30 and the detected temperature of the heat medium inlet temperature thermistor 54 exceeds the first predetermined temperature, or the use side heat medium circuit 30 is heated. When the terminal 32a is used, the case where the temperature detected by the heat medium outlet temperature thermistor 53 exceeds the second predetermined temperature is shown.

It should be noted that the broken line indicates that when the hot water storage tank 32b is used for the use side heat medium circuit 30, the detected temperature of the heat medium inlet temperature thermistor 54 is the first predetermined temperature or less, or the heating terminal 32a is used for the use side heat medium circuit 30. In the case, the temperature detected by the heat medium outlet temperature thermistor 53 is equal to or lower than the second predetermined temperature.

That is, in FIG. 5, when the intermediate pressure rises in a state where the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 exceeds the critical pressure, the intermediate heat exchange of the main refrigerant circuit 10 occurs. The inlet temperature (point A) of the refrigerant of the heat exchanger 13 moves in the direction of increasing enthalpy, and similarly, the outlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 (point e) and the bypass of the intermediate heat exchanger 13 are increased. The outlet temperature (point B) of the refrigerant of the refrigerant circuit 20 also moves in the direction of increasing the enthalpy.

In addition, when the pressure exceeds the critical pressure, the slope of the isotherm with respect to the pressure becomes steeper as the enthalpy increases.

Therefore, even if the intermediate pressure rises in the intermediate heat exchanger 13, in order to obtain the same amount of heat exchange, the refrigerant outlet of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 increases as the intermediate pressure rises. The control device 60 controls the valve opening degree of the second expansion device 21 so that the temperature difference (ΔTM) between the temperature and the inlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 has a large value. There must be.

That is, as the intermediate pressure increases, the temperature difference (ΔTM) between the detected temperature (point B) of the intermediate heat exchanger bypass outlet thermistor 52 and the detected temperature (e) of the intermediate heat exchanger bypass inlet thermistor 56 becomes a large value. Therefore, the control device 60 must control the valve opening degree of the second expansion device 21.

The discharge pressure of the high-stage compression rotary element 11b, the outlet temperature of the refrigerant of the utilization side heat exchanger 12 (point A), and the inlet temperature of the refrigerant of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 (point e). Alternatively, the value of the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is calculated from the temperature of the usage-side heat medium flowing into the usage-side heat exchanger 12.

Then, when the value is equal to or higher than the critical pressure, the higher the pressure of the refrigerant after being decompressed by the second expansion device 21, the higher the pressure of the intermediate heat exchanger 13 based on the calculated value of the intermediate pressure. The control device 60 may control the valve opening degree of the second expansion device 21 so that the temperature difference between the refrigerant outlet temperature and the refrigerant inlet temperature of the bypass refrigerant circuit 20 becomes large.

It should be noted that ΔTM is preset in the control device 60 so that the value of ΔTM increases as the intermediate pressure increases.

Further, in the control device 60, when the heat medium inlet temperature thermistor 54 exceeds the first predetermined temperature, or when the heat medium outlet temperature thermistor 53 exceeds the second predetermined temperature, the heat medium inlet temperature thermistor 54, or As the detected temperature of the heat medium outlet temperature thermistor 53 rises, the valve opening degree of the first expansion device 14 is decreased, the valve opening degree of the second expansion device 21 is increased, and the intermediate pressure is increased. The valve opening of the second expansion device 21 may be controlled so that the value of ΔTM increases as the temperature detected by the heat medium inlet temperature thermistor 54 or the heat medium outlet temperature thermistor 53 increases.

It should be noted that as the inlet temperature of the use side heat medium to the use side heat exchanger 12 or the outlet temperature of the use side heat medium from the use side heat exchanger 12 increases, the value of ΔTM also increases so that the value is controlled. ΔTM is preset in the device 60.

Further, the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b may have a configuration of the compression mechanism 11 configured by two independent compressors, at least the high-stage side compression rotary element. It suffices to reduce the operating frequency of 11b.

Further, the low-stage side compression rotary element 11a and the high-stage side compression rotary element 11b are not divided and may be a single compression rotary element. In the case of a single compression rotary element, the bypass refrigerant circuit 20 The refrigerant from is in the middle of compression of the compression rotary element.

Carbon dioxide is preferably used in the refrigeration cycle device according to the present embodiment. This is because it is possible to raise the temperature of the usage-side heat medium when the usage-side heat medium is heated by carbon dioxide as a refrigerant in the usage-side heat exchanger 12.

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

As described above, the refrigeration cycle apparatus according to the present invention includes the main refrigerant circuit including the intermediate heat exchanger and the bypass refrigerant circuit, and does not reduce the COP by not increasing the differential pressure between the high pressure and the intermediate pressure. It is useful for refrigeration using a refrigeration cycle device, air conditioning, hot water supply, liquid heating device for heating equipment, and the like.

10 Main Refrigerant Circuit 11 Compression Mechanism 11a Lower Stage Compression Rotating Element 11b Higher Stage Compression Rotating 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 Second expansion device 30 Utilization-side heat medium circuit 31 Conveyor device 32a Heating terminal 32b Hot water tank 33 Heat medium pipe 34 First switching valve 35 Second switching valve 41 Hot water tap 42 Hot water heat exchanger 43 Water supply pipe 51 High pressure side pressure detection Device 52 Intermediate heat exchanger bypass outlet thermistor 53 Heat medium outlet temperature thermistor 54 Heat medium inlet temperature thermistor 55a First hot water tank temperature thermistor 55b Second hot water tank temperature thermistor 55c Third hot water tank temperature thermistor 56 Intermediate heat exchanger bypass inlet thermistor 57 Intermediate Heat Exchanger Main Refrigerant Inlet Thermistor 58 Intermediate Heat Exchanger Main Refrigerant Outlet Thermistor 60 Controller

Claims (9)

A compression mechanism including a compression rotary element, a utilization side heat exchanger that heats a utilization side heat medium by a refrigerant discharged from the compression rotation element, an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger are pipes. A main refrigerant circuit formed by sequentially connecting with,
Branched from the pipe between the utilization side heat exchanger and the first expansion device, and after being decompressed by the second expansion device, heat is exchanged with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger, A bypass refrigerant circuit joined to the refrigerant in the middle of compression of the compression rotary element,
A control device,
Equipped with
The temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, the refrigerant is a gas-liquid two-phase Than when flowing in
And,
The temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger,
In order to be in a state larger than the temperature difference between the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the outlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger,
The control device controls the valve opening degree of the second expansion device,
A refrigeration cycle apparatus, wherein the pressure of the refrigerant after being decompressed by the second expansion device is maintained in a state of exceeding a critical pressure. The control is performed such that the higher the pressure of the refrigerant after being decompressed by the second expansion device, the larger the temperature difference between the outlet temperature of the refrigerant and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger. The refrigeration cycle apparatus according to claim 1, wherein the apparatus controls a valve opening degree of the second expansion device. From the pressure value of the refrigerant discharged from the compression mechanism, the refrigerant outlet temperature of the utilization side heat exchanger, and the refrigerant inlet temperature of the bypass refrigerant circuit of the intermediate heat exchanger, The refrigeration cycle apparatus according to claim 1 or 2, wherein it is determined whether or not the pressure of the refrigerant after being decompressed by the 2 expansion device is equal to or higher than a critical pressure. The refrigerating cycle device according to any one of claims 1 to 3, wherein the refrigerant is carbon dioxide. A liquid heating apparatus comprising the refrigeration cycle according to any one of claims 1 to 4, further comprising a usage-side heat medium circuit that circulates the usage-side heat medium by a carrier device. Heat medium outlet temperature thermistor for detecting the temperature of the use side heat medium flowing out from the use side heat exchanger, and heat medium inlet for detecting the temperature of the use side heat medium flowing into the use side heat exchanger. A temperature thermistor, and the control device operates the transfer device so that the detected temperature of the heat medium outlet temperature thermistor becomes a target temperature, and the detected temperature of the heat medium inlet temperature thermistor is a first predetermined value. When the temperature is exceeded, the temperature difference between the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, the refrigerant is Greater than when flowing through the intermediate heat exchanger in a gas-liquid two-phase state, and the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger The temperature difference from the inlet temperature is in a state of being larger than the temperature difference between the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the outlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger. The liquid heating device according to claim 5, wherein the control device controls the valve opening degree of the second expansion device. Heat medium outlet temperature thermistor for detecting the temperature of the use side heat medium flowing out from the use side heat exchanger, and heat medium inlet for detecting the temperature of the use side heat medium flowing into the use side heat exchanger. A temperature thermistor, and the controller operates the transfer device so that a temperature difference between the temperature detected by the heat medium outlet temperature thermistor and the temperature detected by the heat medium inlet temperature thermistor becomes a target temperature difference. In addition, when the detected temperature of the heat medium outlet temperature thermistor exceeds a second predetermined temperature, the outlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger and the bypass refrigerant of the intermediate heat exchanger. The temperature difference with the inlet temperature of the refrigerant of the circuit is larger than when the refrigerant flows through the intermediate heat exchanger in a gas-liquid two-phase state, and the outlet of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger. The temperature difference between the temperature and the inlet temperature of the refrigerant of the main refrigerant circuit of the intermediate heat exchanger, the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger, the main refrigerant of the intermediate heat exchanger The liquid heating device according to claim 5, wherein the control device controls the valve opening degree of the second expansion device so that the temperature difference is larger than the temperature difference from the outlet temperature of the refrigerant of the circuit. .. The control device, the pressure value of the refrigerant discharged from the compression mechanism, the temperature of the use-side heat medium flowing into the use-side heat exchanger, the inlet temperature of the refrigerant of the bypass refrigerant circuit of the intermediate heat exchanger From the above, it is judged whether or not the pressure of the refrigerant after being decompressed by the second expansion device is equal to or higher than a critical pressure, The liquid heating according to any one of claims 5 to 7, apparatus. The liquid heating device according to any one of claims 5 to 8, wherein the use-side heat medium is water or antifreeze.

Images