JP2022175115A - Refrigeration cycle device and liquid heating device including the same - Google Patents

Abstract

To provide a highly reliable refrigeration cycle device by preventing liquid return by causing a superheating degree of a refrigerant which has passed through a supercooling heat exchanger to become a predetermined value or greater, and a liquid heating device including the refrigeration cycle device.SOLUTION: A refrigeration cycle device includes: a main refrigerant circuit 10; a bypass refrigerant circuit 20; a prior-cooling temperature sensor that detects a temperature of a refrigerant flowing in the bypass refrigerant circuit 20 upstream of an intermediate heat exchanger 13; a post-cooling temperature sensor that detects a temperature of a refrigerant flowing in the bypass refrigerant circuit 20 downstream of the intermediate heat exchanger 13; and a control device 60. The control device 60 calculates a superheating degree of the refrigerant to be merged to a compression rotary element on the basis of temperature data acquired from the prior-cooling temperature sensor and the post-cooling temperature sensor, and performs an operation so as to reduce a valve opening of a second expansion device 21 when the calculated superheating degree is below a predetermined value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a refrigerating cycle device and a liquid heating device having the same.

Patent Document 1 discloses a supercritical vapor compression refrigeration cycle equipped with a compressor that compresses a refrigerant in two stages and two expansion devices that expand the refrigerant in two stages, and uses carbon dioxide as the refrigerant. there is
The supercritical vapor compression refrigerating cycle of Patent Document 1 is provided with a gas-liquid separator, and the refrigerant mainly composed of the gas phase in the gas-liquid separator is a refrigerant in the middle of the intermediate connection circuit of the compressor from the injection circuit. The refrigerant is intermediately injected into the mixer, mixed with the refrigerant discharged from the low-stage rotary compression rotary element, and sucked into the high-stage rotary compression rotary element.
In Patent Document 1, the ratio of the displacement volume of the high-stage rotary compression rotary element to the displacement volume of the low-stage rotary compression rotary element (discharged volume ratio) is defined as the suction pressure of the compressor by the refrigerant saturated liquid pressure in the first expansion device. The discharge pressure of the low stage side rotary compression rotary element is set to be equal to or lower than the critical pressure of the refrigerant by setting the value equal to or higher than the root of the isentropic exponent of the quotient obtained by dividing by .
Further, Patent Document 2 discloses a refrigerating device that uses a refrigerant other than carbon dioxide as a refrigerant and includes a compressor that compresses the refrigerant in two stages and two expansion devices that expand the refrigerant in two stages. .
The refrigeration system of Patent Document 2 includes a supercooling heat exchanger and an injection circuit. In the injection circuit, a part of the refrigerant discharged from the compressor is decompressed by a bypass expansion valve, and after the decompressed refrigerant is heated by a subcooling heat exchanger, an intermediate stage that communicates between the low-stage side and the high-stage side of the compressor. Inject into the port. The intermediate port mixes the refrigerant from the injection circuit with the refrigerant discharged from the low stage. The mixed refrigerant is sucked into the high-stage rotating element, and the degree of opening of the bypass expansion valve is adjusted according to the degree of superheat of the sucked refrigerant to prevent the liquid from returning to the compressor.

JP 2010-071643 A JP 2009-192164 A

However, in the conventional configuration, the intermediate port is directly connected to the compression chamber of the compressor, and the refrigerant that has passed through the subcooling heat exchanger (intermediate heat exchanger) is injected into the compression chamber. Thus, in the case of a compressor configured such that the refrigerant to be injected and the refrigerant in the process of being compressed are mixed in the compression chamber and recompressed, if the refrigerant to be injected is a liquid refrigerant, liquid backflow occurs. However, there was a problem that the reliability of the compressor was lowered due to Moreover, it is difficult to directly measure the degree of superheat of the refrigerant after the injected refrigerant and the refrigerant in the process of being compressed are mixed in the compression chamber.

The present invention is intended to solve the above-mentioned problems, and the refrigeration cycle apparatus and its high reliability by preventing liquid backflow by increasing the degree of superheat of the refrigerant after passing through the intermediate heat exchanger to a predetermined value or more. It is an object of the present invention to provide a liquid heating device comprising:

In order to solve the above-described conventional problems, the refrigeration cycle apparatus of the present invention includes a compression mechanism comprising a compression rotary element, and a utilization side heat exchanger that heats a utilization side heat medium with refrigerant discharged from the compression rotary element. , an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger are sequentially connected by piping to form a main refrigerant circuit; and the piping between the user side heat exchanger and the first expansion device. After being decompressed by the second expansion device, the branched refrigerant is heat-exchanged with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger, and is transferred to the refrigerant being compressed by the compression rotary element. a merged bypass refrigerant circuit, a pre-cooling temperature sensor for detecting the temperature of the refrigerant flowing through the bypass refrigerant circuit upstream of the intermediate heat exchanger, and the bypass refrigerant circuit downstream of the intermediate heat exchanger. A post-cooling temperature sensor that detects the temperature of the flowing refrigerant, and a control device, wherein the control device operates the compression rotary element based on temperature data obtained from the pre-cooling temperature sensor and the post-cooling temperature sensor. calculating the degree of superheat of the refrigerant that joins the refrigerant, and if the calculated degree of superheat falls below a predetermined value, the valve opening degree of the second expansion device is reduced. is.
As a result, it is possible to prevent liquid backflow caused by mixing of the liquid refrigerant in the compression chamber of the compression rotary element.

Advantageous Effects of Invention According to the present invention, it is possible to prevent an increase in vibration of the compression mechanism due to the generation of liquid back, and to secure the reliability of the compression mechanism. In particular, when the second expansion valve is opened to a predetermined position at start-up, it is possible to prevent the refrigerant from being gasified and injected as a liquid. can be provided.

1 is a configuration diagram of a liquid heating device according to an embodiment of the present invention; Pressure-enthalpy diagram (Ph diagram) under ideal conditions for the same refrigeration cycle Flow chart of bypass expansion valve control in the present embodiment

(Knowledge, etc. on which this disclosure is based)
In a refrigeration cycle in which refrigerant heated by an intercooler is injected into a compression chamber, the optimum amount of injection varies depending on the outside air temperature and water temperature during operation. Therefore, a common control method is to adjust the amount of refrigerant to be injected using a pressure reducing valve. However, when the injection amount is adjusted, the amount of refrigerant to be injected increases, and the refrigerant on the intermediate pressure side cannot be completely evaporated in the subcooling heat exchanger and flows into the compressor as a liquid. As a result, liquid compression occurs, which may impair the reliability of the compressor. Generally, in order to ensure the reliability of the compressor, control is performed to prevent liquid compression on the suction side, but in the case of a refrigeration cycle with injection, liquid compression during injection is also considered. There is a need to. In order to solve the problem, the subject matter of the present disclosure has been constructed.
Accordingly, the present disclosure provides a highly reliable refrigeration cycle device that prevents liquid backflow of refrigerant that is injected after passing through an intermediate heat exchanger, and a liquid heating device that includes the same.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming more redundant than necessary and to facilitate understanding by those skilled in the art.
It should be noted that the accompanying drawings and the following description are provided to allow those skilled in the art to fully understand the present disclosure and are not intended to limit the claimed subject matter thereby.

(Embodiment)
[1-1. Constitution]
FIG. 1 is a configuration diagram of a liquid heating apparatus according to this embodiment. The liquid heating device is composed of a refrigeration cycle device, which is a supercritical vapor compression refrigeration cycle, and a utilization-side heat medium circuit 30 . Also, the refrigeration cycle device is composed of a main refrigerant circuit 10 and a bypass refrigerant circuit 20 .
The main refrigerant circuit 10 includes a compression mechanism 11 that compresses the refrigerant, a radiator 12 that is a user side heat exchanger, an economizer 13 that is an intermediate heat exchanger, a main expansion valve 14 that is a first expansion device, and a heat source side heat exchanger. are sequentially connected by pipes 16 to form evaporators 15. Carbon dioxide (CO ₂ ) is used as a refrigerant.
As the refrigerant, it is most suitable to use carbon dioxide. Reactive refrigerants can also be used.
The compression mechanism 11 injects the refrigerant from the bypass refrigerant circuit 20 while the rotating element is compressing the refrigerant, joins the refrigerant from the bypass refrigerant circuit 20 and the refrigerant in the middle of compression, and recompresses the refrigerant. The radiator 12 heats the user-side heat medium with the refrigerant discharged from the compression mechanism 11 .

The bypass refrigerant circuit 20 branches off from the pipe 16 between the radiator 12 and the main expansion valve 14 and is connected to a compression chamber in the middle of compression of the compression mechanism 11 .
The bypass refrigerant circuit 20 is provided with a bypass expansion valve 21 as a second expansion device. A part of the high-pressure refrigerant after passing through the radiator 12 or a part of the high-pressure refrigerant after passing through the economizer 13 is decompressed by the bypass expansion valve 21 to become an intermediate-pressure refrigerant, and then the economizer 13 passes through the main refrigerant circuit. It exchanges heat with the high-pressure refrigerant flowing through 10 , is injected into the rotating element of the compression mechanism 11 , and joins with the refrigerant in the middle of compression in the main refrigerant circuit 10 .

The utilization-side heat medium circuit 30 is formed by sequentially connecting the radiator 12 , the conveying pump 31 that is a conveying device, and the heating terminal 32 a with a heat medium pipe 33 . Water or antifreeze is used as the heat medium on the user side.
The use-side heat medium circuit 30 in the present embodiment includes a hot water storage tank 32b in parallel with the heating terminal 32a. Alternatively, the hot water is circulated to the hot water storage tank 32b. In addition, the utilization side heat medium circuit 30 may be provided with either the heating terminal 32a or the hot water storage tank 32b.

The high-temperature water generated by the radiator 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 by the radiator 12 again.
The hot water generated by the radiator 12 is introduced into the hot water tank 32b from the upper part of the hot water tank 32b, and the low temperature water is drawn out from the lower part of the hot water tank 32b and heated by the radiator 12.

The hot water supply heat exchanger 42 is arranged in the hot water storage tank 32b, and heat-exchanges 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 valve 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 a predetermined temperature at the hot water supply valve 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 supply heat exchanger 42, and supplied from the hot water tap 41 and the high-temperature water in the hot water storage tank 32b are indirectly heated so as not to mix with each other. .
The hot water supply heat exchanger 42 is a water heat exchanger using copper pipes or stainless steel pipes as heat transfer pipes, and as shown in FIG. is connected to the hot water supply heat exchanger 42 . The water supply pipe 43 introduces normal temperature water to the lower end of the hot water supply heat exchanger 42, that is, to the lower part of the hot water storage tank 32b. The normal temperature water introduced into the hot water supply heat exchanger 42 through the water supply pipe 43 takes heat from the high temperature water in the hot water storage tank 32b while moving upward in the hot water storage tank 32b, and the high temperature water is heated. As a result, hot water is supplied from the hot water tap 41 .

In the hot water storage tank 32b, a plurality of hot water storage tank temperature thermomistors measure the temperature of hot water at a plurality of different height positions. For example, a first hot water storage tank temperature thermistor 55a, a second hot water storage tank temperature thermistor 55b, and a third hot water storage tank temperature thermistor 55c are provided. Normal temperature water entering the hot water supply heat exchanger 42 through the water supply pipe 43 takes heat from high temperature water in the hot water storage tank 32b while moving upward in the hot water storage tank 32b. Therefore, the hot water in the hot water storage tank 32b naturally has a high temperature in the upper part and a low temperature in the lower part.

In the main refrigerant circuit 10 , a high-pressure side pressure detection device 51 is provided in the pipe 16 on the discharge side of the compression mechanism 11 . The high pressure side pressure detection device 51 is provided in the main refrigerant circuit 10 from the discharge side of the compression mechanism 11 to the upstream side of the main expansion valve 14 . The high-pressure side pressure detection device 51 only needs to detect the pressure of the high-pressure refrigerant in the main refrigerant circuit 10 .
An intermediate heat exchanger main refrigerant inlet thermistor 57 is provided in the piping 16 on the downstream side of the user-side heat exchanger 12 in the main refrigerant circuit 10 and on the upstream side of the economizer 13 . The intermediate heat exchanger main refrigerant inlet thermistor 57 detects the temperature of the refrigerant flowing out of the user-side heat exchanger 12 . Further, the bypass refrigerant circuit 20 is provided with an intermediate heat exchanger bypass inlet thermistor 56 . Intermediate heat exchanger bypass inlet thermistor 56 senses the temperature of the refrigerant exiting second expansion device 21 downstream of second expansion device 21 and upstream of economizer 13 .
The utilization-side heat medium circuit 30 also includes a heat-medium outlet temperature thermistor 53 that detects the temperature of the utilization-side heat medium flowing out of the utilization-side heat exchanger 12, and and a heat medium inlet temperature thermistor 54 for detecting temperature.

Further, the bypass refrigerant circuit 20 includes an intermediate heat exchanger bypass inlet thermistor 56 that detects the refrigerant temperature on the upstream side of the economizer 13, an intermediate heat exchanger bypass outlet thermistor 58 that detects the refrigerant temperature on the downstream side, and a second expansion device. 21 is provided with an intermediate pressure side pressure detection device 52 that directly or indirectly detects the pressure on the downstream side.
When the intermediate pressure side pressure detection device 52 directly detects the pressure, the intermediate pressure side pressure detection device 52 is a pressure detection device that directly, that is, mechanically detects the pressure of the refrigerant.
When the intermediate pressure side pressure detection device 52 indirectly detects the pressure, it is based on the detected pressure detected by the high pressure side pressure detection device 51 and the detected temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57. or based on the temperature detected by the heat medium inlet temperature thermistor 54 and the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56. The control device 60 calculates the value of the pressure (intermediate pressure). The control device 60 has an arithmetic processing function.
That is, the controller 60 stores a pressure-enthalpy diagram (Ph diagram) as shown in FIG.

Then, the high-pressure side pressure detector 51 detects the high-pressure side pressure (discharge pressure of the high-stage compression rotary element 11b), and the intermediate heat exchanger main refrigerant inlet thermistor 57 detects the refrigerant outlet temperature (point A) of the user-side heat exchanger 12. , the intermediate heat exchanger bypass inlet thermistor 56 detects the inlet temperature (point e) of the refrigerant in the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 at predetermined intervals.
Then, based on the ideal condition that the enthalpy at point A and point e are approximately the same value, the control device 60 calculates the pressure and enthalpy at point e, so that 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 determine whether or not the pressure is equal to or higher than the critical pressure based on the calculated value.
Note that the detected temperature detected by the heat medium inlet temperature thermistor 54 may be used instead of the detected temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57, since the values are substantially the same.
That is, the discharge pressure of the compression mechanism 11, the refrigerant outlet temperature (point A) of the utilization side heat exchanger 12, the refrigerant inlet temperature (point e) of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13, or It can be determined from the temperature of the use-side heat medium flowing into the 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.

It should be noted that the intermediate pressure side pressure detection device 52 may be provided with either one of pressure detection devices that directly or indirectly detect pressure.
The control device 60 controls the compression mechanism 11 based on the pressure detected by the high pressure side pressure detection device 51 and the intermediate pressure side pressure detection device 52 and the temperature detected by the heat medium outlet temperature thermistor 53 and the heat medium inlet temperature thermistor 54. The operating frequency, the opening degrees of the main expansion valve 14 and the bypass expansion valve 21, and the transfer pump 31 are controlled.

[1-2. motion]
FIG. 2 is a pressure-enthalpy diagram (Ph diagram) under ideal conditions for the refrigeration cycle apparatus according to the present embodiment. indicates that the high pressure is equal to or higher than the predetermined pressure. Points a to e and points AB in FIG. 2 correspond to respective points in the liquid heating apparatus shown in FIG.

The operation of the refrigeration cycle apparatus will be described with reference to FIG.
First, the high-pressure refrigerant (point a) discharged from the compression mechanism 11 is branched from the main refrigerant circuit 10 at the refrigerant branch point A after radiating heat in the radiator 12, and is decompressed to the intermediate pressure by the bypass expansion valve 21. The intermediate-pressure refrigerant, which becomes the refrigerant (point e), exchanges heat in the economizer 13 .
The high-pressure refrigerant flowing through the main refrigerant circuit 10 after dissipating heat in the radiator 12 is cooled by the intermediate-pressure refrigerant (point e) flowing through the bypass refrigerant circuit 20, and the main expansion valve 14 is in a state where the enthalpy is reduced (point b). is decompressed at
As a result, the refrigerant enthalpy of the refrigerant (point c) flowing into the evaporator 15 after being decompressed by the main expansion valve 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 evaporator 15 decreases and the liquid component of the refrigerant increases, it contributes to evaporation in the evaporator 15, and the refrigerant ratio increases, the amount of heat absorbed from the outside air increases, and returns to the suction side of the compression mechanism 11 (point d).
On the other hand, an amount of refrigerant corresponding to the amount of gaseous components that do not contribute to evaporation in the evaporator 15 is bypassed to the bypass refrigerant circuit 20 and becomes low-temperature intermediate-pressure refrigerant (point e). The intermediate-pressure refrigerant is heated by the high-pressure refrigerant flowing through the main refrigerant circuit 10 in the economizer 13 to increase the refrigerant enthalpy, and reaches the refrigerant junction B in the middle of compression in the compression mechanism 11 .
Therefore, at the confluence point (point B) of the compression mechanism 11, since the refrigerant pressure is higher than that on the suction side (d point) of the compression mechanism 11, the refrigerant density is also high. Furthermore, since the refrigerant is compressed by the compression mechanism 11 and discharged, the flow rate of the refrigerant flowing into the radiator 12 is greatly increased, and the ability to heat water, which is the heat medium on the utilization side, is greatly increased.

When the discharge pressure of the compression mechanism 11 rises and exceeds a predetermined value, the control device 60 controls the pressure of the refrigerant after being decompressed by the bypass expansion valve 21 to reach the critical pressure as shown in FIG. 2(b). control of the valve opening degree of the bypass expansion valve 21 is started so that the state exceeds .
Specifically, when the control device 60 determines that the detected pressure detected by the high pressure side pressure detection device 51 has increased and exceeds the first predetermined high pressure value, the detection pressure detected by the intermediate pressure side pressure detection device 52 is increased. When the pressure is below the critical pressure, the bypass expansion valve 21 is started to open to a greater degree.
Then, as shown in FIG. 2B, the control device 60 operates to increase the valve opening degree of the bypass expansion valve 21 and increases the operating frequency of the compression mechanism 11 so that the bypass refrigerant circuit 20 is increased so that the detected pressure detected by the high pressure side pressure detecting device 51 becomes the second predetermined high pressure value, which is the target high pressure value. The second predetermined high pressure value is higher than the first predetermined high pressure value.

At the same time, when the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is less than the critical pressure as shown in FIG. , the valve opening degree of the bypass expansion valve 21 is controlled. On the downstream side of the economizer 13 in the bypass refrigerant circuit 20, when the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before joining is acquired (S1), and it is determined that the degree of superheat SHm has fallen below a predetermined value SHt ( If YES in S2), the degree of opening of the bypass expansion valve 21 is decreased to decrease the flow rate of the refrigerant (S3). As a result, the temperature of the refrigerant increases due to heat exchange with the main refrigerant circuit 10 , and the degree of superheat SHm between the refrigerant being compressed in the compression mechanism 11 and the refrigerant before joining increases downstream of the economizer 13 . Therefore, the refrigerant injected into the compression mechanism 11 becomes gas. Further, when it is determined that the acquired degree of superheat SHm of the refrigerant on the downstream side of the economizer 13 exceeds the predetermined value SHt (NO in S2), the bypass expansion valve 21 is operated to increase the valve opening degree, and the flow rate of the refrigerant is increased. is increased (S4). As a result, the extent of temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10 is reduced, and the degree of superheat SHm of the refrigerant in the process of compression and the refrigerant before joining in the compression mechanism 11 on the downstream side of the economizer 13 is reduced. The temperature of the refrigerant that joins the main refrigerant circuit 10 during compression of the mechanism 11 decreases, and the discharge temperature, which is the temperature of the refrigerant discharged from the compression mechanism 11, decreases.
At this time, the degree of superheat SHm of the refrigerant injected into the compression mechanism 11 is the temperature obtained from the intermediate heat exchanger bypass inlet thermistor 56 and the intermediate heat exchanger bypass outlet thermistor 58 after considering the pressure loss of the economizer 13. It can be calculated from the difference. This is because the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56 is the saturation temperature when the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is less than the critical pressure. . It can also be calculated from pressure information detected by the intermediate pressure side pressure detector 52 and temperature information detected by the intermediate heat exchanger bypass outlet thermistor 58 .

The operation when the hot water storage tank 32b is used in the utilization side heat medium circuit 30 will be described below.
Among the plurality of hot water storage tank temperature thermistors, for example, when the temperature detected by the first hot water storage tank temperature thermistor 55a arranged at the highest position in the hot water storage tank 32b is less than a predetermined value, high-temperature water is supplied to the hot water storage tank 32b. is insufficient, the controller 60 determines.
Then, the control device 60 operates the compression mechanism 11 to heat the low-temperature water with the radiator 12 so that the temperature detected by the heat medium outlet temperature thermistor 53, which is the temperature generated by heating, becomes equal to the target temperature. Then, the conveying pump 31 is operated.
As a result, the radiator 12 heats the low-temperature water drawn out from the lower portion of the hot water storage tank 32b. As a result, high-temperature water is generated, and the generated high-temperature water is introduced into the hot water tank 32b from the upper portion of the hot water tank 32b. At this time, the temperature detected by the heat medium inlet temperature thermistor 54 is lower than or equal to the third predetermined temperature, so the operation is performed in the state shown in FIG. 2(a).
Since hot water is gradually stored in the hot water storage tank 32b from the top, the detected temperature detected by the heat medium inlet temperature thermistor 54 gradually rises, but is detected by the heat medium inlet temperature thermistor 54. When the detected temperature exceeds the third predetermined temperature, the operation is performed in the state shown in FIG. 2(b).

That is, the control device 60 operates to increase the degree of opening of the bypass expansion valve 21 and increases the operating frequency of the compression mechanism 11 to increase the circulation amount of the refrigerant flowing through the bypass refrigerant circuit 20, The detected pressure detected by the high-pressure side pressure detector 51 is set to the second predetermined high pressure value, which is the target high pressure value. At the same time, the control device 60 causes the detected pressure detected by the intermediate pressure side pressure detection device 52 to become the predetermined intermediate pressure value, which is the target intermediate pressure value.
As a result, the inlet temperature of the heat medium to the radiator 12 increases, and the refrigerant heating capacity of the radiator 12 is increased to compensate for the decrease in the enthalpy difference (aA) of the refrigerant in the radiator 12. , to maintain the supply of hot water to the hot water storage tank 32b.
Then, when the temperature detected by the heat medium inlet temperature thermistor 54 exceeds a first predetermined temperature higher than the third predetermined temperature, the control device 60 reduces the operating frequency of the compression mechanism 11 so that heat is dissipated. High-temperature water can be stored in the hot water storage tank 32b while suppressing the pressure rise of the high-pressure refrigerant in the radiator 12 so that the pressure of the high-pressure refrigerant in the vessel 12 does not exceed the second predetermined high-pressure value, which is the target high-pressure value. .

As the thresholds, instead of the third predetermined temperature and the first predetermined temperature, which are the temperatures detected by the heat medium inlet temperature thermistor 54, the first temperature, which is the detected pressure detected by the high pressure side pressure detection device 51, is used. Similar operational actions may be performed using the predetermined high pressure value and the second predetermined high pressure value.

A case where the heating terminal 32a is used for the heat medium circuit 30 on the utilization side will be described.
The controller 60 operates the compression mechanism 11 and heats the circulating water with the radiator 12. The temperature difference between the circulating water, which is detected by the heat medium outlet temperature thermistor 53 and the heat medium inlet temperature thermistor 54, is The conveying pump 31 is operated so that the temperature difference from the detection temperature detected in 1 becomes the target temperature difference.
As a result, the high-temperature water generated by the radiator 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 by the radiator 12 again. 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 a target temperature difference, and the heat medium outlet temperature thermistor Since the detected temperature detected by 53 is equal to or lower than the fourth predetermined temperature, it operates in the state shown in FIG. 2(a).
Since the heating load gradually decreases, control is performed 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. Therefore, the temperature detected by the heat medium outlet temperature thermistor 53 and the temperature detected by the heat medium inlet temperature thermistor 54 gradually increase. When the fourth predetermined temperature is exceeded, the operation is performed in the state shown in FIG. 2(b).

That is, the bypass expansion valve 21 is operated to increase the valve opening degree, and the operating frequency of the compression mechanism 11 is increased to increase the circulation amount of the refrigerant flowing through the bypass refrigerant circuit 20, thereby increasing the high-pressure side pressure detection device. The detected pressure detected at 51 is set to the second predetermined high pressure value, which is the target high pressure value.

At the same time, when the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is less than the critical pressure, the control device 60 controls the bypass expansion valve 21 as shown in the control flow of FIG. Control the degree of opening. On the downstream side of the economizer 13 in the bypass refrigerant circuit 20, when the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before joining is acquired (S1), and it is determined that the degree of superheat SHm has fallen below a predetermined value SHt ( If YES in S2), the degree of opening of the bypass expansion valve 21 is decreased to reduce the flow rate of the refrigerant (S3). As a result, the temperature of the refrigerant increases due to heat exchange with the main refrigerant circuit 10 , and the degree of superheat SHm between the refrigerant being compressed in the compression mechanism 11 and the refrigerant before joining increases downstream of the economizer 13 . Therefore, the refrigerant injected into the compression mechanism 11 becomes gas. Further, when it is determined that the acquired degree of superheat SHm of the refrigerant on the downstream side of the economizer 13 exceeds the predetermined value SHt (NO in S2), the bypass expansion valve 21 is operated to increase the valve opening degree, and the flow rate of the refrigerant is increased. is increased (S4). As a result, the extent of temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10 is reduced, and the degree of superheat SHm of the refrigerant in the process of compression and the refrigerant before joining in the compression mechanism 11 on the downstream side of the economizer 13 is reduced. The temperature of the refrigerant that joins the main refrigerant circuit 10 during compression of the mechanism 11 decreases, and the discharge temperature, which is the temperature of the refrigerant discharged from the compression mechanism 11, decreases.
At this time, the degree of superheat SHm of the refrigerant injected into the compression mechanism 11 is the temperature obtained from the intermediate heat exchanger bypass inlet thermistor 56 and the intermediate heat exchanger bypass outlet thermistor 58 after considering the pressure loss of the economizer 13. It can be calculated from the difference. This is because the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56 becomes the saturation temperature when the pressure (intermediate pressure) of the refrigerant after being decompressed by the second expansion device 21 is less than the critical pressure. . The calculation can also be performed from pressure information detected by the intermediate pressure side pressure detector 52 and temperature information detected by the intermediate heat exchanger bypass outlet thermistor 58 .
As a result, the heating load is reduced, and the enthalpy difference (aA) in the radiator 12 is reduced by increasing the refrigerant heating capacity in the radiator 12, so that high-temperature water is supplied to the heating terminal 32a. is maintained.

Then, when the detected temperature detected by the heat medium outlet temperature thermistor 53 exceeds a second predetermined temperature higher than the fourth predetermined temperature, the operating frequency of the compression mechanism 11 is lowered to reduce the high pressure in the radiator 12. It can be used as a heating device using high-temperature water while suppressing the pressure rise of the high-pressure refrigerant in the radiator 12 so that the pressure of the refrigerant does not exceed the second predetermined high-pressure value, which is the target high-pressure value.

[1-3. effects, etc.]
On the downstream side of the economizer 13 in the bypass refrigerant circuit 20, when the degree of superheat SHm of the refrigerant in the middle of compression in the compression mechanism 11 and the refrigerant before joining falls below a predetermined value SHt, the degree of opening of the bypass expansion valve 21 is reduced. As a result, the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before joining together increases on the downstream side of the economizer 13 . Therefore, the refrigerant injected into the compression mechanism 11 can be prevented from being compressed in a liquid state.
Further, when the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before being merged exceeds a predetermined value SHt on the downstream side of the economizer 13, the valve opening degree of the bypass expansion valve 21 is increased. As a result, on the downstream side of the economizer 13, the degree of superheat SHm of the refrigerant in the middle of compression in the compression mechanism 11 and the refrigerant before merging decreases, and the discharge temperature, which is the temperature of the refrigerant discharged from the compression mechanism 11, also decreases. Therefore, it is possible to suppress an excessive rise in the discharge temperature exceeding the use range.
For these reasons, the reliability of the compression mechanism 11 is ensured by controlling the degree of superheat SHm of the refrigerant during compression and the refrigerant before joining the compression mechanism 11 downstream of the economizer 13 using the bypass expansion valve 21. can do. The predetermined value SHt for increasing the opening degree of the bypass expansion valve 21 and the predetermined value SHt for decreasing the opening degree of the bypass expansion valve 21 may be the same or different. good. That is, the predetermined value SHt for increasing the degree of opening of the bypass expansion valve 21 may be greater than the predetermined value SHt for decreasing the degree of opening of the bypass expansion valve 21 .

Instead of the fourth predetermined temperature and the second predetermined temperature, which are the temperatures detected by the heat medium outlet temperature thermistor 53, as the threshold values, the first Similar operational actions may be performed using the predetermined high pressure value and the second predetermined high pressure value.

In the refrigeration cycle apparatus according to the present embodiment, carbon dioxide is preferably used as the refrigerant. This is because, in the radiator 12, the temperature of the utilization-side heat medium can be increased when the utilization-side heat medium is heated with carbon dioxide, which is a refrigerant.
In addition, by using water or antifreeze as the heat medium to be used, it can be used for the heating terminal 32a, or high-temperature water can be stored in the hot water storage tank 32b.

As described above, the refrigeration cycle apparatus according to the present invention comprises a main refrigerant circuit and a bypass refrigerant circuit provided with an intermediate heat exchanger, and sets the degree of superheat of the refrigerant injected from the bypass refrigerant circuit to the compression mechanism to a predetermined value or more. As a result, it is possible to prevent the occurrence of liquid compression in the compression mechanism, and thus it is useful for refrigeration, air conditioning, hot water supply, liquid heating devices using a refrigeration cycle device, and the like.

10 main refrigerant circuit 11 compression mechanism 12 radiator (utilization side heat exchanger)
13 economizer (intermediate heat exchanger)
14 main expansion valve (first expansion device)
15 evaporator (heat source side heat exchanger)
16 piping 20 bypass refrigerant circuit 21 bypass expansion valve (second expansion device)
30 Heat medium circuit on the user side 31 Conveying pump (conveying device)
32a heating terminal 32b hot water storage tank 33 heat medium pipe 34 first switching valve 35 second switching valve 41 hot water tap 42 hot water supply heat exchanger 43 water supply pipe 51 high pressure side pressure detector 52 intermediate pressure side pressure detector 53 heat medium outlet temperature thermistor 54 Heat medium inlet temperature thermistor 55a First hot water storage tank temperature thermistor 55b Second hot water storage tank temperature thermistor 55c Third hot water storage tank temperature thermistor 56 Intermediate heat exchanger bypass inlet thermistor (pre-cooling temperature sensor)
57 Intermediate heat exchanger main refrigerant inlet thermistor 58 Intermediate heat exchanger bypass outlet thermistor (post-cooling temperature sensor)
60 control device

Claims (10)

A compression mechanism composed of a compression rotary element, a utilization side heat exchanger for heating a utilization side heat medium with refrigerant discharged from the compression rotary element, an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger. a main refrigerant circuit formed by sequentially connecting pipes;
After the refrigerant is branched from the pipe between the user-side heat exchanger and the first expansion device, and the branched refrigerant is depressurized by the second expansion device, the main refrigerant circuit is passed through the intermediate heat exchanger. a bypass refrigerant circuit that exchanges heat with the flowing refrigerant and joins the refrigerant that is being compressed by the compression rotary element;
a pre-cooling temperature sensor that detects the temperature of the refrigerant flowing through the bypass refrigerant circuit on the upstream side of the intermediate heat exchanger;
a post-cooling temperature sensor that detects the temperature of the refrigerant flowing through the bypass refrigerant circuit downstream of the intermediate heat exchanger;
a control device;
The control device calculates the degree of superheat of the refrigerant joining the compression rotary element based on the temperature data acquired from the pre-cooling temperature sensor and the post-cooling temperature sensor, and the calculated degree of superheat is A refrigeration cycle apparatus characterized in that, when the second expansion device is below a predetermined value, the valve opening degree of the second expansion device is reduced. The control device calculates the degree of superheat of the refrigerant joining the compression rotary element based on the temperature data obtained from the pre-cooling temperature sensor and the post-cooling temperature sensor, and the calculated superheat 2. The refrigeration cycle apparatus according to claim 1, wherein when the degree of opening of the second expansion device is greater than or equal to the predetermined value, the valve opening degree of the second expansion device is increased. an intermediate pressure side pressure detection device that detects the pressure of the refrigerant flowing through the bypass refrigerant circuit downstream of the second expansion device;
When the detected pressure detected by the intermediate pressure side pressure detecting device is equal to or lower than the critical pressure, the control device operates to increase the opening degree of the valve of the second expansion device. Item 3. The refrigeration cycle device according to Item 2. 4. The refrigeration cycle apparatus according to claim 3, wherein said control device increases the operating frequency of said compression rotary element. A high-pressure side pressure detection device that detects the pressure on the high-pressure side of the main refrigerant circuit,
5. The apparatus according to claim 4, wherein when the detected pressure detected by said high pressure side pressure detecting device exceeds a predetermined value, said control device reduces said operating frequency of said compression rotary element. Refrigeration cycle equipment. 6. The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein the refrigerant is carbon dioxide. A liquid heating apparatus comprising: the refrigeration cycle apparatus according to any one of claims 1 to 5; and a utilization-side heat medium circuit that circulates the utilization-side heat medium by a conveying device. a heat medium outlet temperature thermistor for detecting the temperature of the heat transfer medium flowing out of the use heat exchanger;
a heat medium inlet temperature thermistor that detects the temperature of the use-side heat medium flowing into the use-side heat exchanger;
The control device operates the conveying device so that the detected temperature detected by the heat medium outlet temperature thermistor becomes equal to a target temperature, and the detected temperature detected by the heat medium inlet temperature thermistor is set to a first predetermined temperature. 8. A liquid heating apparatus according to claim 7, wherein the operating frequency of said compression rotating element is reduced when the temperature exceeds. a heat medium outlet temperature thermistor for detecting the temperature of the heat transfer medium flowing out of the use heat exchanger;
a heat medium inlet temperature thermistor that detects the temperature of the use-side heat medium flowing into the use-side heat exchanger;
The control device operates the conveying device such that the 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. 8. The liquid heating apparatus according to claim 7, wherein when the detected temperature of the heat medium outlet temperature thermistor exceeds a second predetermined temperature, the operating frequency of the compression rotary element is lowered. 10. The liquid heating apparatus according to any one of claims 7 to 9, wherein the heat medium on the utilization side is water or antifreeze liquid.

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