Refrigeration cycle device and liquid heating device equipped with the same

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

[Technical field]

[0001] The present invention relates to a refrigeration cycle device and a liquid heating device including the same. [Background technology]

[0002] Patent Document 1 discloses a supercritical vapor compression refrigeration cycle that includes 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. The supercritical vapor compression refrigeration cycle of Patent Document 1 is equipped with a gas-liquid separator, and the refrigerant mainly composed of a gas phase in the gas-liquid separator is intermediately injected from an injection circuit into a refrigerant mixer located midway through the intermediate connection circuit of the compressor, mixed with the refrigerant discharged from the low-stage side rotary compression rotating element, and sucked into the high-stage side rotary compression rotating 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 (displacement volume ratio) is set to be equal to or greater than the isentropic exponential root of the quotient obtained by dividing the suction pressure of the compressor by the refrigerant saturation liquid pressure in the first expansion device, thereby making the discharge pressure of the low-stage rotary compression rotary element equal to or less than the critical pressure of the refrigerant. Furthermore, Patent Document 2 discloses a refrigeration system that uses a refrigerant other than carbon dioxide as the refrigerant and is equipped with a compressor that compresses the refrigerant in two stages and two expansion devices that expand the refrigerant in two stages. The refrigeration device of Patent Document 2 includes a subcooling heat exchanger and an injection circuit. The injection circuit reduces the pressure of a portion of the refrigerant discharged from the compressor using a bypass expansion valve, and after heating the reduced pressure refrigerant using the subcooling heat exchanger, injects the refrigerant into an intermediate port that communicates with the low-stage side and high-stage side of the compressor. In the intermediate port, the refrigerant from the injection circuit and the refrigerant discharged from the low-stage side are mixed. The mixed refrigerant is sucked into the high-stage rotating element, and the opening of the bypass expansion valve is adjusted according to the degree of superheat of the sucked refrigerant to prevent liquid return to the compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-071643 A [Patent Document 2] JP 2009-192164 A Summary of the Invention [Problem to be solved by the invention]

[0004] 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. In this way, in the case of a compressor configured such that the injected refrigerant and the refrigerant in the middle of compression are mixed in the compression chamber and recompressed, if the injected refrigerant is a liquid refrigerant, liquid backflow occurs, which reduces the reliability of the compressor. In addition, it is difficult to directly measure the degree of superheat of the refrigerant after the injected refrigerant and the refrigerant in the middle of compression are mixed in the compression chamber.

[0005] The present invention is devised to solve the above-mentioned problems, and aims to provide a highly reliable refrigeration cycle device and a liquid heating device equipped with the same, which prevent liquid backflow by increasing the superheat degree of the refrigerant after passing through an intermediate heat exchanger to a predetermined value or higher. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the refrigeration cycle device of the present invention includes a compression mechanism including a compression rotary element, a use-side heat exchanger that heats a use-side heat medium with a refrigerant discharged from the compression rotary element, an intermediate heat exchanger, a first expansion device, and a heat source-side heat exchanger that are successively connected by piping, a bypass refrigerant circuit that is branched from the piping between the use-side heat exchanger and the first expansion device, and the branched refrigerant is decompressed by a second expansion device, and then heat-exchanged with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger and merged with the refrigerant being compressed by the compression rotary element, a pre-cooling temperature sensor that detects a temperature of the refrigerant flowing through the bypass refrigerant circuit upstream of the intermediate heat exchanger, and a post-cooling temperature sensor that detects a temperature of the refrigerant flowing through the bypass refrigerant circuit downstream of the intermediate heat exchanger. a high-pressure side pressure detection device for detecting a pressure on a high-pressure side of the main refrigerant circuit, and an intermediate-pressure side pressure detection device for detecting a pressure of the refrigerant flowing through the bypass refrigerant circuit downstream of the second expansion device; and a control device, the control device being configured to, when the detected pressure detected by the high pressure side pressure detection device exceeds a predetermined value, The above The valve opening of the bypass expansion valve is operated so that the detected pressure detected by the intermediate pressure side pressure detection device exceeds a critical pressure, and when the detected pressure detected by the intermediate pressure side pressure detection device is less than the critical pressure, the degree of superheat of the refrigerant to be merged into the compression rotating element is calculated based on temperature data obtained from the pre-cooling temperature sensor and the post-cooling temperature sensor, and when the calculated degree of superheat is below a predetermined value, the valve opening of the second expansion device is operated to be reduced, and when the calculated degree of superheat is equal to or greater than the predetermined value, the valve opening of the second expansion device is operated to be increased. This makes it possible to prevent liquid backflow, which occurs when liquid refrigerant enters the compression chamber of the compression rotary element. Effect of the Invention

[0007] According to the present invention, it is possible to prevent an increase in vibration of the compression mechanism due to the occurrence of liquid backflow and ensure 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 injected in liquid form without being gasified, thereby providing a highly reliable refrigeration cycle device and a liquid heating device equipped with the same. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a liquid heating device according to an embodiment of the present invention. [Diagram 2] Pressure-enthalpy diagram (Ph diagram) under ideal conditions for the same refrigeration cycle [Diagram 3] Flow diagram of bypass expansion valve control in this embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (The knowledge and other information that formed the basis of this disclosure) In a refrigeration cycle in which a refrigerant heated by an intermediate cooler is injected into a compression chamber, the optimal amount of injection varies depending on the outside air temperature and water temperature during operation. Therefore, a general control method is to adjust the amount of refrigerant to be injected using a pressure reducing valve. However, when adjusting the injection amount, the amount of refrigerant to be injected increases, and the refrigerant on the intermediate pressure side does not evaporate completely in the subcooling heat exchanger and flows into the compressor as a liquid. This may cause liquid compression to occur, which may impair the reliability of the compressor. In general, in order to ensure the reliability of the compressor, control is performed to prevent liquid compression on the suction side, but in addition to that, in the case of a refrigeration cycle with injection, it is also necessary to consider liquid compression during injection. In order to solve this problem, the subject of the present disclosure has been constituted. Therefore, the present disclosure provides a highly reliable refrigeration cycle device that prevents liquid backflow of the refrigerant injected after passing through an intermediate heat exchanger, and a liquid heating device including the same.

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation 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 enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] (Embodiment) [1-1. Configuration] 1 is a configuration diagram of a liquid heating device according to the present embodiment. The liquid heating device is composed of a refrigeration cycle device, which is a supercritical vapor compression refrigeration cycle, and a user-side heat medium circuit 30. The refrigeration cycle device is also composed of a main refrigerant circuit 10 and a bypass refrigerant circuit 20. The main refrigerant circuit 10 is formed by sequentially connecting a compression mechanism 11 that compresses the refrigerant, a radiator 12 that is a utilization-side heat exchanger, an economizer 13 that is an intermediate heat exchanger, a main expansion valve 14 that is a first expansion device, and an evaporator 15 that is a heat source-side heat exchanger through piping 16. Carbon dioxide (CO 2 ) is used. It is best to use carbon dioxide as the refrigerant, but it is also possible to use non-azeotropic refrigerants such as R407C, pseudo-azeotropic refrigerants such as R410A, or a single refrigerant such as R32, or a flammable refrigerant such as propane. The compression mechanism 11 injects the refrigerant from the bypass refrigerant circuit 20 while the rotating elements are compressing the refrigerant, and recompresses the refrigerant by merging the refrigerant from the bypass refrigerant circuit 20 with the refrigerant being compressed. The radiator 12 heats the utilization-side heat medium with the refrigerant discharged from the compression mechanism 11.

[0012] 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 located midway through compression in the compression mechanism 11. The bypass refrigerant circuit 20 is provided with a bypass expansion valve 21 serving as a second expansion device. A portion of the high-pressure refrigerant after passing through the radiator 12, or a portion of the high-pressure refrigerant after passing through the economizer 13 is reduced in pressure by the bypass expansion valve 21 to become an intermediate-pressure refrigerant, and then undergoes heat exchange with the high-pressure refrigerant flowing through the main refrigerant circuit 10 in the economizer 13. The intermediate-pressure refrigerant is then injected into the rotating elements of the compression mechanism 11 and merges with the refrigerant in the main refrigerant circuit 10 that is being compressed.

[0013] The utilization side heat medium circuit 30 is formed by sequentially connecting the radiator 12, a transfer pump 31 which is a transfer device, and a heating terminal 32a with a heat medium pipe 33. Water or antifreeze liquid is used as the utilization side heat medium. The use-side heat medium circuit 30 in this embodiment includes a heating terminal 32a and a hot water storage tank 32b in parallel, and the use-side heat medium is circulated to the heating terminal 32a or the hot water storage tank 32b by switching a first switching valve 34 and a second switching valve 35. The use-side heat medium circuit 30 may include either the heating terminal 32a or the hot water storage tank 32b.

[0014] The high-temperature water generated in the radiator 12 dissipates heat at the heating terminal 32a and is used for heating, and the low-temperature water whose heat has been dissipated at the heating terminal 32a is heated again by the radiator 12. Moreover, high-temperature water generated in the radiator 12 is introduced into the hot water storage tank 32b from the upper part of the hot water storage tank 32b, and low-temperature water is discharged from the lower part of the hot water storage tank 32b and heated by the radiator 12.

[0015] The hot water heat exchanger 42 is disposed in the hot water storage tank 32b, and exchanges heat between the water supplied 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, adjusted to a predetermined temperature by the hot water tap 41, and supplied from the hot water tap 41. Note that 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 indirectly heated and do not mix with each other. The hot water heat exchanger 42 is a water heat exchanger that uses copper pipes or stainless steel pipes as heat transfer pipes, and as shown in Fig. 1, a water supply pipe 43 extending from a water supply source (tap water) and a hot water tap 41 are connected to the hot water heat exchanger 42. The water supply pipe 43 introduces room temperature water to the lower end of the hot water heat exchanger 42, i.e., to the lower part of the hot water storage tank 32b. The room temperature water introduced from the water supply pipe 43 to the hot water heat exchanger 42 moves from the lower part to the upper part of the hot water storage tank 32b, removing heat from the high temperature water in the hot water storage tank 32b, and becomes high temperature heated water, which is supplied from the hot water tap 41.

[0016] In the hot water tank 32b, a plurality of hot water tank temperature thermometers measure the temperature of the hot water at a plurality of different height positions. For example, a first hot water tank temperature thermistor 55a, a second hot water tank temperature thermistor 55b, and a third hot water tank temperature thermistor 55c are provided. The room temperature water that enters the hot water supply heat exchanger 42 from the water supply pipe 43 moves from the bottom to the top inside the hot water tank 32b and absorbs heat from the high temperature water inside the hot water tank 32b. Therefore, the hot water inside the hot water tank 32b naturally has a high temperature at the top and a low temperature at the bottom.

[0017] In the main refrigerant circuit 10, a high-pressure side pressure detecting device 51 is provided in the piping 16 on the discharge side of the compression mechanism 11. The high-pressure side pressure detecting 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. It is sufficient for the high-pressure side pressure detecting device 51 to be able to detect the pressure of the high-pressure refrigerant in the main refrigerant circuit 10. Furthermore, an intermediate heat exchanger main refrigerant inlet thermistor 57 is provided in the pipe 16 downstream of the user side heat exchanger 12 in the main refrigerant circuit 10 and upstream of the economizer 13. The intermediate heat exchanger main refrigerant inlet thermistor 57 detects the temperature of the refrigerant flowing out from the user side heat exchanger 12. Furthermore, the bypass refrigerant circuit 20 is provided with an intermediate heat exchanger bypass inlet thermistor 56. The intermediate heat exchanger bypass inlet thermistor 56 is downstream of the second expansion device 21 and upstream of the economizer 13, and detects the temperature of the refrigerant flowing out from the second expansion device 21. The use-side heat medium circuit 30 also includes a heat medium outlet temperature thermistor 53 that detects the temperature of the use-side heat medium flowing out of the use-side heat exchanger 12, and a heat medium inlet temperature thermistor 54 that detects the temperature of the use-side heat medium flowing into the use-side heat exchanger 12.

[0018] Furthermore, the bypass refrigerant circuit 20 is equipped with an intermediate heat exchanger bypass inlet thermistor 56 that detects the refrigerant temperature upstream of the economizer 13, an intermediate heat exchanger bypass outlet thermistor 58 that detects the refrigerant temperature downstream of the economizer 13, and an intermediate pressure side pressure detection device 52 that directly or indirectly detects the pressure downstream of the second expansion device 21. When the intermediate pressure side pressure detecting device 52 detects the pressure directly, the intermediate pressure side pressure detecting device 52 is a pressure detecting device that detects the pressure of the refrigerant directly, that is, mechanically. When the intermediate pressure side pressure detecting device 52 indirectly detects the pressure, the control device 60 calculates the value of the pressure (intermediate pressure) of the refrigerant after being reduced in pressure by the second expansion device 21 based on the detected pressure detected by the high pressure side pressure detecting device 51 and the detected temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57, or based on the detected temperature detected by the heat medium inlet temperature thermistor 54 and the detected temperature detected by the intermediate heat exchanger bypass inlet thermistor 56. The control device 60 has a calculation processing function. That is, the control device 60 stores a pressure-enthalpy diagram (Ph diagram) as shown in FIG.

[0019] Then, the high-pressure side pressure detection device 51 detects the high-pressure side pressure (the discharge pressure of the high-stage side compression rotating element 11b), the intermediate heat exchanger main refrigerant inlet thermistor 57 detects the refrigerant outlet temperature (point A) of the utilization side heat exchanger 12, and the intermediate heat exchanger bypass inlet thermistor 56 detects the refrigerant inlet temperature (point e) of the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 at predetermined time intervals. Then, based on the ideal condition that the enthalpy at points A and e is approximately the same value, the control device 60 calculates the pressure and enthalpy at point e, thereby calculating the value of the pressure (intermediate pressure) of the refrigerant after it has been reduced in pressure by the second expansion device 21, and can use this value to determine whether it is above the critical pressure. It should be noted that, instead of the temperature detected by the intermediate heat exchanger main refrigerant inlet thermistor 57, the temperature detected by the heat medium inlet temperature thermistor 54 may be used since the values ​​are substantially the same. In other words, it is possible to determine whether the pressure of the refrigerant (intermediate pressure) after being reduced in pressure by the second expansion device 21 is equal to or higher than the critical pressure based on the discharge pressure of the compression mechanism 11, the outlet temperature of the refrigerant from the use side heat exchanger 12 (point A), and the inlet temperature of the refrigerant from the bypass refrigerant circuit 20 of the intermediate heat exchanger 13 (point e), or the temperature of the use side heat medium flowing into the use side heat exchanger 12.

[0020] The intermediate pressure side pressure detecting device 52 may be a pressure detecting device that detects pressure directly or indirectly. The control device 60 controls the operating frequency of the compression mechanism 11, the valve openings of the main expansion valve 14 and the bypass expansion valve 21, and the conveying pump 31 based on the detected pressures detected by the high-pressure side pressure detection device 51 and the intermediate-pressure side pressure detection device 52, and the detected temperatures detected by the heat medium outlet temperature thermistor 53 and the heat medium inlet temperature thermistor 54.

[0021] [1-2. Operation] Fig. 2 shows a pressure-enthalpy diagram (Ph diagram) under ideal conditions for the refrigeration cycle device of this embodiment, with Fig. 2(a) showing a case where the high pressure is less than a predetermined pressure, and Fig. 2(b) showing a case where the high pressure is equal to or greater than a predetermined pressure. Points a to e and points A to B in Fig. 2 correspond to the respective points in the liquid heating device shown in Fig. 1.

[0022] The operation of the refrigeration cycle device will be described with reference to FIG. First, the high-pressure refrigerant (point a) discharged from the compression mechanism 11 dissipates heat in the radiator 12, then branches off from the main refrigerant circuit 10 at the refrigerant branching point A, and is reduced in pressure to an intermediate pressure by the bypass expansion valve 21 to become an intermediate-pressure refrigerant (point e), which undergoes heat exchange 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 flowing through the bypass refrigerant circuit 20 (point e), and is reduced in pressure by the main expansion valve 14 in a state in which its enthalpy is reduced (point b). This also reduces the refrigerant enthalpy of the refrigerant (point c) flowing into the evaporator 15 after being decompressed by the main expansion valve 14. The refrigerant dryness (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, which contributes to evaporation in the evaporator 15, increases the refrigerant ratio, and increases the amount of heat absorbed from the outside air, and returns to the suction side of the compression mechanism 11 (point d). On the other hand, the refrigerant in an amount equivalent to the amount of gas phase components that do not contribute to evaporation in the evaporator 15 is bypassed to the bypass refrigerant circuit 20 and becomes a 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 and reaches the refrigerant junction point B during compression in the compression mechanism 11 in a state in which the refrigerant enthalpy has been increased. Therefore, at the confluence point (point B) of compression mechanism 11, the refrigerant pressure is higher than that on the suction side (point d) of compression mechanism 11, and the refrigerant density is also higher. In addition, the refrigerant that joins with the refrigerant being compressed in compression mechanism 11 is further compressed and discharged in compression mechanism 11. As a result, the refrigerant flow rate flowing into radiator 12 increases significantly, and the capacity to heat water, which is the heat medium on the user side, increases significantly.

[0023] When the discharge pressure of the compression mechanism 11 increases and exceeds a predetermined value, the control device 60 starts to control the valve opening degree of the bypass expansion valve 21 so that the pressure of the refrigerant after being reduced in pressure by the bypass expansion valve 21 exceeds the critical pressure as shown in FIG. 2(b). Specifically, when the control device 60 determines that the detected pressure detected by the high-pressure side pressure detection device 51 has risen and exceeded a first predetermined high pressure value, if the detected pressure detected by the intermediate-pressure side pressure detection device 52 is below the critical pressure, the control device 60 begins operation to increase the valve opening of the bypass expansion valve 21. 2(b), the control device 60 operates the bypass expansion valve 21 to increase the valve opening degree and also increases the operating frequency of the compression mechanism 11 to increase the amount of refrigerant circulating through the bypass refrigerant circuit 20, so that the pressure detected by the high-pressure side pressure detection device 51 becomes the second predetermined high-pressure value, which is the target high-pressure value. Note that the second predetermined high-pressure value is a value higher than the first predetermined high-pressure value.

[0024] At the same time, as shown in FIG. 2(a), 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 valve opening of the bypass expansion valve 21 as shown in the control flow of FIG. 3. The controller 60 acquires the superheat degree SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before being merged on the downstream side of the economizer 13 of the bypass refrigerant circuit 20 (S1), and when it is determined that the superheat degree SHm falls below a predetermined value SHt (YES in S2), the controller 60 operates the bypass expansion valve 21 to reduce the valve opening and reduce the flow rate of the refrigerant (S3). As a result, the temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10 becomes large, and the superheat degree SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before being merged on the downstream side of the economizer 13 increases. Therefore, the refrigerant injected into the compression mechanism 11 becomes gas. Furthermore, when it is determined that the acquired superheat degree SHm of the refrigerant downstream of the economizer 13 exceeds the predetermined value SHt (NO in S2), the valve opening of the bypass expansion valve 21 is increased to increase the flow rate of the refrigerant (S4). This reduces the range of temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10, and the superheat degree SHm of the refrigerant before merging with the refrigerant being compressed in the compression mechanism 11 downstream of the economizer 13 decreases, the temperature of the refrigerant that merged with the main refrigerant circuit 10 during compression in the compression 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 can be calculated from the difference in temperature obtained from the intermediate heat exchanger bypass inlet thermistor 56 and the intermediate heat exchanger bypass outlet thermistor 58, taking into consideration the pressure loss of the economizer 13. This is because, when the pressure (intermediate pressure) of the refrigerant after being reduced in pressure by the second expansion device 21 is less than the critical pressure, the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56 becomes the saturation temperature. Note that it can also be calculated from pressure information detected by the intermediate pressure side pressure detection device 52 and temperature information detected by the intermediate heat exchanger bypass outlet thermistor 58.

[0025] Hereinafter, the operation in the case where the hot water storage tank 32b is used in the utilization side heat medium circuit 30 will be described. If the detected temperature detected by, for example, the first hot water tank temperature thermistor 55a, which is located at the highest position of the hot water tank 32b among the multiple hot water tank temperature thermistors, is below a predetermined value, the control device 60 determines that there is not enough high-temperature water in the hot water tank 32b. Then, the control device 60 operates the compression mechanism 11 to heat the low-temperature water in the radiator 12, and operates the conveying pump 31 so that the detected temperature detected by the heat medium outlet temperature thermistor 53, which is the heating generation temperature, becomes equal to the target temperature. As a result, the low-temperature water discharged from the bottom of the hot water storage tank 32b is heated by the radiator 12. As a result, high-temperature water is generated, and the generated high-temperature water is introduced into the hot water storage tank 32b from the top 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 third predetermined temperature, the system operates in the state shown in FIG. 2(a). Then, since high-temperature water is gradually stored in the hot water storage tank 32b from the top, the temperature detected by the heat medium inlet temperature thermistor 54 gradually increases, but when the temperature detected by the heat medium inlet temperature thermistor 54 exceeds a third predetermined temperature, the device operates in the state shown in Figure 2(b).

[0026] That is, the control device 60 operates the bypass expansion valve 21 to increase the valve opening degree and raises the operating frequency of the compression mechanism 11 to increase the amount of refrigerant circulating through the bypass refrigerant circuit 20, so that the pressure detected by 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 control device 60 adjusts the 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 enthalpy difference (aA) of the refrigerant in the radiator 12 decreases, so that the heating capacity of the refrigerant in the radiator 12 is increased, thereby making it possible to maintain the supply of high-temperature water to the hot water storage tank 32b. When the detected temperature detected by the heat medium inlet temperature thermistor 54 exceeds a first predetermined temperature which is higher than the third predetermined temperature, the control device 60 reduces the operating frequency of the compression mechanism 11, thereby enabling high-temperature water to be stored in the hot water storage tank 32b while suppressing a pressure increase of the high-pressure refrigerant in the radiator 12 so that the pressure of the high-pressure refrigerant in the radiator 12 does not exceed a second predetermined high-pressure value which is the target high-pressure value.

[0027] In addition, a similar operating operation may be performed by using, as threshold values, a first predetermined high pressure value and a second predetermined high pressure value, which are the detected pressures detected by the high-pressure side pressure detection device 51, instead of the third predetermined temperature and the first predetermined temperature, which are the detected temperatures detected by the heat medium inlet temperature thermistor 54.

[0028] A case where the heating terminal 32a is used in the utilization side heat medium circuit 30 will be described. The control device 60 operates the compression mechanism 11 and heats the circulating water in the radiator 12, and operates the conveying pump 31 so that the temperature difference of the circulating water, that is, the temperature difference between the detected temperature detected by the heat medium outlet temperature thermistor 53 and the detected temperature detected by the heat medium inlet temperature thermistor 54, becomes a target temperature difference. As a result, the high-temperature water generated in the radiator 12 radiates heat at the heating terminal 32a and is used for heating, and the low-temperature water radiated heat at the heating terminal 32a is heated again by the radiator 12. 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 detected temperature detected by the heat medium outlet temperature thermistor 53 is equal to or lower than the fourth predetermined temperature, so that the system operates in the state shown in FIG. Then, as the heating load gradually decreases, the temperature difference between the temperature detected by heat medium outlet temperature thermistor 53 and the temperature detected by heat medium inlet temperature thermistor 54 is controlled to become the target temperature difference, so the temperatures detected by heat medium outlet temperature thermistor 53 and the temperature detected by heat medium inlet temperature thermistor 54 gradually increase. However, when the temperature detected by heat medium outlet temperature thermistor 53 exceeds the fourth predetermined temperature, the operation is made in the state shown in FIG. 2(b).

[0029] In other words, the bypass expansion valve 21 is operated to increase its valve opening, and the operating frequency of the compression mechanism 11 is increased to increase the amount of refrigerant circulating through the bypass refrigerant circuit 20, so that the detected pressure detected by the high-pressure side pressure detection device 51 becomes the second specified high-pressure value, which is the target high-pressure value.

[0030] 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 valve opening of the bypass expansion valve 21 as shown in the control flow of Fig. 3. The controller 60 acquires the superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging downstream of the economizer 13 of the bypass refrigerant circuit 20 (S1), and when it is determined that the superheat SHm falls below a predetermined value SHt (YES in S2), the controller 60 operates the bypass expansion valve 21 to reduce the valve opening and reduce the flow rate of the refrigerant (S3). As a result, the temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10 becomes large, and the superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging downstream of the economizer 13 increases. Therefore, the refrigerant injected into the compression mechanism 11 becomes gas. Furthermore, when it is determined that the acquired superheat degree SHm of the refrigerant downstream of the economizer 13 exceeds the predetermined value SHt (NO in S2), the valve opening of the bypass expansion valve 21 is increased to increase the flow rate of the refrigerant (S4). This reduces the range of temperature rise of the refrigerant due to heat exchange with the main refrigerant circuit 10, and the superheat degree SHm of the refrigerant before merging with the refrigerant being compressed in the compression mechanism 11 downstream of the economizer 13 decreases, the temperature of the refrigerant that merged with the main refrigerant circuit 10 during compression in the compression 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 can be calculated from the difference in temperature obtained from the intermediate heat exchanger bypass inlet thermistor 56 and the intermediate heat exchanger bypass outlet thermistor 58, taking into consideration the pressure loss of the economizer 13. This is because, when the pressure (intermediate pressure) of the refrigerant after being reduced in pressure by the second expansion device 21 is less than the critical pressure, the temperature detected by the intermediate heat exchanger bypass inlet thermistor 56 becomes the saturation temperature. Note that the calculation can also be performed from pressure information detected by the intermediate pressure side pressure detection device 52 and temperature information detected by the intermediate heat exchanger bypass outlet thermistor 58. As a result, the heating load is reduced, and the smaller enthalpy difference (aA) in the radiator 12 is compensated for by increasing the heating capacity of the refrigerant in the radiator 12, thereby making it possible to maintain the supply of high-temperature water to the heating terminal 32a.

[0031] When the temperature detected by the heat medium outlet temperature thermistor 53 exceeds a second predetermined temperature which is higher than the fourth predetermined temperature, the operating frequency of the compression mechanism 11 is lowered, so that the pressure of the high-pressure refrigerant in the radiator 12 does not exceed the second predetermined high-pressure value which is the target high-pressure value, while suppressing the pressure increase of the high-pressure refrigerant in the radiator 12, and the device can be used as a heating device using high-temperature water.

[0032] [1-3. Effects, etc.] When the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging falls below a predetermined value SHt downstream of the economizer 13 in the bypass refrigerant circuit 20, the valve opening of the bypass expansion valve 21 is operated to decrease, thereby increasing the degree of superheat SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging downstream of the economizer 13. This makes it possible to prevent the refrigerant injected into the compression mechanism 11 from being compressed in a liquid state. In addition, when the superheat degree SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging downstream of the economizer 13 exceeds a predetermined value SHt, the bypass expansion valve 21 is operated to increase the valve opening degree, thereby decreasing the superheat degree SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging downstream of the economizer 13 and decreasing the discharge temperature, which is the temperature of the refrigerant discharged from the compression mechanism 11. Therefore, an excessive rise in the discharge temperature that exceeds the operating range can be suppressed. For these reasons, the reliability of the compression mechanism 11 can be ensured by using the bypass expansion valve 21 to control the superheat degree SHm of the refrigerant being compressed in the compression mechanism 11 and the refrigerant before merging, downstream of the economizer 13. Note that the predetermined value SHt for increasing the valve opening degree of the bypass expansion valve 21 and the predetermined value SHt for decreasing the valve opening degree of the bypass expansion valve 21 may be the same as or different from each other. In other words, the predetermined value SHt for increasing the valve opening degree of the bypass expansion valve 21 may be larger than the predetermined value SHt for decreasing the valve opening degree of the bypass expansion valve 21.

[0033] In addition, a similar operating operation may be performed by using, as threshold values, a first predetermined high pressure value and a second predetermined high pressure value, which are the detected pressures detected by the high-pressure side pressure detection device 51, instead of the fourth predetermined temperature and the second predetermined temperature, which are the detected temperatures detected by the heat medium outlet temperature thermistor 53.

[0034] In the refrigeration cycle device according to the present embodiment, it is preferable to use carbon dioxide as the refrigerant. This is because, when the utilization side heat medium is heated by the carbon dioxide refrigerant in the radiator 12, the utilization side heat medium can be heated to a high temperature. Furthermore, by using water or antifreeze liquid as the heat medium on the utilization side, it is possible to use it in the heating terminal 32a, or to store high-temperature water in the hot water storage tank 32b. [Industrial Applicability]

[0035] INDUSTRIAL APPLICABILITY As described above, the refrigeration cycle device of the present invention comprises a main refrigerant circuit equipped with an intermediate heat exchanger and a bypass refrigerant circuit, and by setting the degree of superheat of the refrigerant injected from the bypass refrigerant circuit to a compression mechanism at a predetermined value or higher, it is possible to prevent liquid compression from occurring in the compression mechanism. Therefore, the refrigeration cycle device is useful for liquid heating devices for refrigeration, air conditioning, hot water supply, and heating appliances using the refrigeration cycle device. [Explanation of symbols]

[0036] 10 Main refrigerant circuit 11 Compression mechanism 12 Heat radiator (User 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 User-side heat carrier circuit 31 Conveyor pump (conveyor device) 32a Heating terminal 32b Hot water tank 33 Heat medium piping 34 First switching valve 35 Second switching valve 41 Hot water tap 42 Hot water heat exchanger 43 Water supply piping 51 High pressure side pressure detection device 52 Intermediate pressure side pressure detection device 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 3rd hot water 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

1. a main refrigerant circuit formed by sequentially connecting a compression mechanism including a compression rotary element, a utilization side heat exchanger that heats a utilization side heat medium with the refrigerant discharged from the compression rotary element, an intermediate heat exchanger, a first expansion device, and a heat source side heat exchanger through piping; a bypass refrigerant circuit in which the refrigerant is branched from the piping between the utilization side heat exchanger and the first expansion device, the branched refrigerant is decompressed by a second expansion device, and then heat-exchanged with the refrigerant flowing through the main refrigerant circuit in the intermediate heat exchanger, and is joined to the refrigerant being compressed in the compression rotary element; a pre-cooling temperature sensor that detects a temperature of the refrigerant flowing through the bypass refrigerant circuit upstream of the intermediate heat exchanger; a post-cooling temperature sensor that detects a temperature of the refrigerant flowing through the bypass refrigerant circuit downstream of the intermediate heat exchanger; a high-pressure side pressure detection device for detecting the pressure on the high-pressure side of the main refrigerant circuit; 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; Control device and Equipped with The control device includes: When the detected pressure detected by the high pressure side pressure detection device exceeds a predetermined value, the valve opening of the bypass expansion valve is operated so that the detected pressure detected by the intermediate pressure side pressure detection device exceeds a critical pressure, A refrigeration cycle device characterized in that, when the detected pressure detected by the intermediate pressure side pressure detection device is less than the critical pressure, the degree of superheat of the refrigerant to be merged into the compression rotating element is calculated based on temperature data obtained from the pre-cooling temperature sensor and the post-cooling temperature sensor, and when the calculated degree of superheat is below a predetermined value, the valve opening of the second expansion device is operated to be reduced, and when the calculated degree of superheat is equal to or greater than the predetermined value, the valve opening of the second expansion device is operated to be increased.

2. A refrigeration cycle apparatus as described in Claim 1, characterized in that when the detected pressure detected by the high-pressure side pressure detection device exceeds a predetermined value, the control device increases the operating frequency of the compression rotating element.

3. A refrigeration cycle apparatus as described in Claim 2, characterized in that when the detected pressure detected by the high-pressure side pressure detection device exceeds a predetermined value, the control device reduces the operating frequency of the compression rotating element.

4. 4. The refrigeration cycle device according to claim 1, wherein the refrigerant is carbon dioxide.

5. A liquid heating device comprising: the refrigeration cycle device according to any one of claims 1 to 4; and a utilization-side heat medium circuit that circulates the utilization-side heat medium by a transport device.

6. a heat medium outlet temperature thermistor for detecting a temperature of the use-side heat medium flowing out from the use-side heat exchanger; a heat medium inlet temperature thermistor for detecting the temperature of the use-side heat medium flowing into the use-side heat exchanger; Equipped with The liquid heating device according to claim 5, characterized in that 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 reduces the operating frequency of the compression rotating element when the detected temperature detected by the heat medium inlet temperature thermistor exceeds a first predetermined temperature.

7. a heat medium outlet temperature thermistor for detecting a temperature of the use-side heat medium flowing out from the use-side heat exchanger; a heat medium inlet temperature thermistor for detecting the temperature of the use-side heat medium flowing into the use-side heat exchanger; Equipped with The liquid heating device according to claim 5, characterized in that the control device operates the conveying device so that a temperature difference between a detected temperature detected by the heat medium outlet temperature thermistor and a detected temperature detected by the heat medium inlet temperature thermistor becomes a target temperature difference, and reduces an operating frequency of the compression rotating element when the detected temperature of the heat medium outlet temperature thermistor exceeds a second predetermined temperature.

8. 8. The liquid heating device according to claim 5, wherein the utilization side heat medium is water or an antifreeze liquid.

Images