JP2007051841A - Refrigeration cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability of a compressor by preventing injection of liquid refrigerant in an injection cycle using carbon dioxide refrigerant. <P>SOLUTION: This device comprises elements such as an injection compressor 101, a radiator 102 and a heat releasing blower 128, a branch part 103, a first expansion valve 104, a second expansion valve 106, a heat absorber 107 and a heat absorbing blower 129, a first internal heat exchanger 126, a second internal heat exchanger 125 that is a second heat exchange means, a flow control valve 141, a first pipe temperature sensor 112, a second pipe temperature sensor 142, an evaporation temperature sensor 143 and an injection circuit controller 110. The first expansion valve 104 is controlled based on the difference in detection temperature between the evaporation temperature sensor 143 and the first pipe temperature sensor 112, and the flow control valve 141 is controlled based on the difference in detection temperature between the evaporation temperature sensor 143 and the second pipe temperature sensor 142. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus using an injection cycle. In particular, the present invention relates to a technique for improving performance and reliability during cooling overload operation in a configuration including a heat exchanger that uses carbon dioxide as a refrigerant and exchanges heat between refrigerants.

  Conventionally, a technique of a vapor compression refrigeration cycle that prevents an increase in size of a compressor or the like without impairing the refrigeration capacity of the vapor compression refrigeration cycle that exceeds a critical pressure using carbon dioxide has been disclosed (for example, Patent Document 1). reference).

  As shown in FIG. 3, this technique includes a compression device 301, a radiator 302, a branching portion 303, a first decompression device 304, a cooler 305, a second decompression device 306, an evaporator 307, and the like. Furthermore, accumulator 308, control device 310, temperature sensor 311 for detecting the temperature of the cooled blown air, temperature sensor 312 for detecting the temperature of the refrigerant to be injected, pressure sensor 313 for detecting the pressure of the refrigerant to be injected, and room temperature sensor 314, an outdoor temperature sensor 315, a temperature setting means 316, a temperature sensor 317 for detecting the outlet refrigerant temperature of the radiator 302, a pressure sensor 318 for detecting the outlet refrigerant pressure, blowers 328 and 329, and the like constitute the entire apparatus. is doing. Further, here, arrows 330 and 331 indicate blown air.

In FIG. 3, the carbon dioxide refrigerant that has passed through the radiator 302 is branched by the branching portion 303, and one of them is decompressed by the first decompression device 304 as an injection refrigerant, and the decompressed refrigerant and the refrigerant on the other side are cooled. At 305, heat is exchanged to cool the other refrigerant. Thereby, since the specific enthalpy of the refrigerant on the other side on the inlet side of the second decompression device 306 can be reduced, the specific enthalpy difference between the inlet and the outlet of the evaporator 307 can be increased. Accordingly, it is possible to prevent an increase in the size of each device such as the compression device 301 without impairing the refrigerating capacity.
JP-A-10-288411

  However, in the conventional apparatus described in Patent Document 1, no accumulator is provided in the injection refrigerant path, and it is said that the superheat degree is maintained at about 5K at which the liquid refrigerant is not injected by the first decompression device. There is a problem that a change in the cycle state due to a change in the operating frequency of the machine, a change in the indoor air flow, etc. cannot be handled only by the first decompression device, and an excessive amount of liquid refrigerant may be injected to cause a compressor failure. is there.

  The present invention solves the above-mentioned conventional problems, and even if a change in cycle state occurs due to a change in the operating frequency of the compressor or a change in the indoor air volume, the state of the injection refrigerant is controlled, and particularly the liquid refrigerant is used. An object of the present invention is to provide a highly reliable refrigeration cycle apparatus that prevents injection.

In order to solve the above-described conventional problems, the refrigeration cycle apparatus of the present invention includes a second heat exchange for exchanging heat with a high-pressure refrigerant in an intermediate-pressure inlet side path of the refrigerant that has exited the first decompression means. A bypass path having a flow control valve is provided between the first heat exchange means and the first heat exchange means, and the refrigerant exiting the first pressure reduction means passes through the bypass path from the second heat exchange means or the first heat. It is led to the intermediate pressure inlet of the injection compressor through the exchange means. Thereby, the heat exchange capability of the refrigerant | coolant which exited the 1st pressure reduction means and the refrigerant | coolant which exited the thermal radiation means can be changed rapidly.

  In order to solve the above-described conventional problem, the refrigeration cycle apparatus of the present invention includes an evaporating temperature detecting means for detecting the evaporating temperature of the refrigerant in the second heat exchanging means, and an outlet at the outlet of the second heat exchanging means. A first refrigerant temperature detecting means for detecting the temperature of the refrigerant that has exited the first decompression means, and a second that detects the temperature of the refrigerant that has exited the first decompression means before the intermediate pressure inlet after joining the bypass path. The refrigerant temperature detection means is provided, and the detection temperature of the evaporation temperature detection means is compared with the detection temperatures of the first refrigerant temperature detection means and the second refrigerant temperature detection means. Thereby, the superheat degree of the refrigerant can be detected only by the temperature detecting means, and can be monitored at two locations.

  The refrigeration cycle apparatus of the present invention is operated with the flow control valve normally opened and returning the refrigerant from the bypass path to the intermediate pressure suction port, and the dryness of the refrigerant returning to the intermediate pressure suction port is reduced due to a change in the operation state. In this case, the flow control valve is closed, and all of the refrigerant that has exited the first pressure reducing means passes through the first heat exchanging means after exiting the second heat exchanging means, and the refrigerant returning to the intermediate pressure suction port It can respond quickly to changes in dryness to prevent liquid return and improve reliability.

  Further, the refrigeration cycle apparatus of the present invention compares the detected temperature of the evaporating temperature detecting means with the detected temperatures of the first refrigerant temperature detecting means and the second refrigerant temperature detecting means, and determines the degree of superheat of the refrigerant. The detection is performed only by the detection means and monitoring is performed at two locations, and the reliability of the control can be improved with an inexpensive configuration.

  According to a first aspect of the present invention, a bypass path having a flow rate control valve is provided between the second heat exchanging means and the first heat exchanging means in the refrigerant path exiting the first pressure reducing means, and the first pressure reducing means The refrigerant that has exited is guided from the second heat exchange means through the bypass path or through the first heat exchange means to the intermediate pressure suction port of the injection compressor. When the flow control valve is normally opened and the refrigerant is returned to the intermediate pressure suction port from the bypass path, the flow control valve is operated when the dryness of the refrigerant returning to the intermediate pressure suction port decreases due to a change in the operation state. All of the refrigerant that has exited the first pressure reducing means passes through the first heat exchanging means after leaving the second heat exchanging means, and the change in the dryness of the refrigerant returning to the intermediate pressure suction port It can respond quickly to prevent liquid return and improve reliability.

  In the second invention, in particular, in the first invention, the position where the high-pressure refrigerant branches to the first decompression means is located before the first heat exchange means, and the cold heat of the refrigerant passing through the first decompression means. Is all given to the refrigerant passing through the second decompression means, and the heat absorption means absorbs heat, so that an apparatus with excellent refrigerating performance can be provided.

  According to a third aspect of the present invention, in particular, in the first aspect, the position where the high-pressure refrigerant branches to the first decompression unit is between the first heat exchange unit and the second heat exchange unit. Since the refrigerant passing through the decompression means exchanges heat with the refrigerant having a large circulation amount before leaving the heat dissipation means and branching, the heating capacity of the refrigerant passing through the first decompression means in the first heat exchange means is high, It is possible to provide a highly reliable device that has a high ability to prevent liquid return to the intermediate pressure inlet.

  According to a fourth aspect of the invention, in particular, in the first to third aspects of the invention, the injection circuit control means detects the temperature detected by the evaporation temperature detection means, the detection temperature of the first refrigerant temperature detection means, and the detection temperature of the second refrigerant temperature detection means. Thus, the degree of superheat of the refrigerant is detected only by the temperature detection means and monitored at two locations, and the reliability of control can be improved with an inexpensive configuration.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the first pressure reducing means in the fourth aspect of the invention compares the detected temperature of the evaporation temperature detecting means with the detected temperature of the second refrigerant temperature detecting means so that the temperature difference becomes a predetermined value. And the flow rate control valve is operated so that the temperature difference becomes a predetermined value by comparing the detected temperature of the evaporating temperature detecting means with the detected temperature of the first refrigerant temperature detecting means. Therefore, highly reliable control can be performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to a first embodiment of the present invention. As shown in FIG. 1, an injection compressor 101, a radiator 102 and a heat radiating fan 128 as heat radiating means, a branching portion 103 for diverting the radiated high-pressure refrigerant, a first expansion valve 104 as a first pressure reducing means, A second expansion valve 106 serving as a second pressure reducing means, a heat absorber 107 serving as a heat absorbing means, a blower 129 for heat absorption, a first internal heat exchanger 126 serving as a first heat exchanging means, and a second heat exchanging means. The second internal heat exchanger 125, the flow rate control valve 141, the first pipe temperature sensor 112 as the first refrigerant temperature detection means, the second pipe temperature sensor 142 as the second refrigerant temperature detection means, and the evaporation temperature detection means It is comprised by elements, such as a certain evaporation temperature sensor 143 and the injection circuit control apparatus 110.

  A high-temperature, high-pressure, supercritical carbon dioxide refrigerant (hereinafter referred to as a refrigerant) sent from the discharge port 150 of the injection compressor 101 is cooled by the radiator 102 and then the first expansion valve 104 at the branch portion 103. It is divided into an intermediate pressure inlet side path 153 heading toward and a low pressure inlet side path 154 heading toward the first internal heat exchanger 126.

  In the intermediate pressure inlet side path 153, the refrigerant flowing from the branch portion 103 to the first expansion valve 104 is decompressed and expanded by the first expansion valve 104 and then flows to the second internal heat exchanger 125. Then, the second internal heat exchanger 125 is divided while flowing at the branching portion 103 and flows to the first internal heat exchanger 126, and then absorbs heat and evaporates from the other refrigerant flowing to the second internal heat exchanger 125. , It flows to the first internal heat exchanger 126 and further absorbs heat, or passes through the flow control valve 141 without passing through the first internal heat exchanger 126 and returns to the intermediate pressure inlet 151 of the injection compressor 101. .

  On the other hand, in the low-pressure inlet side path 154, the refrigerant that has flowed from the branch portion 103 through the first internal heat exchanger 126 and the second internal heat exchanger 125 and has been cooled while being in the supercritical state passes through the second expansion valve 106. It expands under reduced pressure, absorbs heat in the heat absorber 107 and evaporates, and returns to the low pressure inlet 152 of the injection compressor 101. An accumulator 108 is provided in front of the low-pressure suction port 152 to prevent liquid return from being sucked in the liquid state.

  The capacity of the refrigeration cycle in the first embodiment is that if the heat dissipation capacity of the radiator 102 is the same, the amount of refrigerant passing through the heat absorber 107 is lower than that of the refrigeration cycle in which injection is not performed, but the first internal heat exchange The capacity is not greatly changed because it is cooled by the condenser 126 and the second internal heat exchanger 125. Strictly speaking, the specific enthalpy of the intermediate pressure inlet 151 is reduced by an amount smaller than the specific enthalpy of the low pressure inlet 152. However, the reduction of the refrigerant compressed from the low pressure to the high pressure reduces the compression power and improves the overall efficiency.

In the first embodiment, in the stable state, the flow control valve 141 is set to fully open, and the first expansion valve 104 is detected by the temperature detected by the evaporation temperature sensor 143 and the first pipe temperature sensor 11.
The detected temperature of 2 is controlled by the injection circuit control device 110 so as to maintain a predetermined temperature difference. Thus, since it is set as the structure which compares with the detection temperature of the evaporation temperature sensor 143, it can comprise at low cost, without using an expensive pressure sensor.

  Actually, it is desirable to set the detection temperature of the first piping temperature sensor 112 to be about 3K higher than the detection temperature of the evaporation temperature sensor 143. The temperature of the refrigerant after the refrigerant passing through the flow control valve 141 and the refrigerant further heated through the first internal heat exchanger 126 merge, that is, the detected temperature of the second pipe temperature sensor 142 is the evaporation temperature sensor 143. It becomes higher by about 5-6K than the detected temperature.

  When the operating frequency of the injection compressor 101 is changed, or when the air flow of the heat dissipating blower 128 or the heat absorbing blower 129 is changed, the balance of the refrigeration cycle changes, and the first temperature relative to the detected temperature of the evaporation temperature sensor 143 changes. When the temperature detected by the pipe temperature sensor 112 is lowered, the first expansion valve 104 is throttled to control the temperature difference. However, since the control speed of the first expansion valve 104 is suppressed to avoid instability, the detected temperature difference between the evaporation temperature sensor 143 and the first pipe temperature sensor 112 may not be maintained. At this time, the detected temperature of the second pipe temperature sensor 142 is also relatively lowered with respect to the detected temperature of the evaporation temperature sensor 143.

  In the series control of the first expansion valve 104 and the flow rate control valve 141, the final purpose is to ensure the degree of superheat of the refrigerant in the intermediate pressure inlet 151, and the temperature detected by the second pipe temperature sensor 142 is the evaporation temperature sensor 143. The temperature is about 5-6K higher than the detected temperature. Therefore, when the detected temperature of the second piping temperature sensor 142 is relatively lowered with respect to the detected temperature of the evaporation temperature sensor 143, the injection circuit control device 110 throttles the flow control valve 141, and finally. Cut off.

  By this operation, the refrigerant passing through the flow control valve 141 decreases and the refrigerant heated through the first internal heat exchanger 126 increases, so that the second pipe temperature sensor 142 detects the detected temperature of the evaporation temperature sensor 143. It is possible to suppress the temperature from being relatively lowered and prevent the liquid from returning to the intermediate pressure inlet 151.

(Embodiment 2)
FIG. 2 is a configuration diagram of a refrigeration cycle apparatus according to a second embodiment of the present invention. The second embodiment is different from the first embodiment in that a first internal heat exchanger 226 that is a first heat exchange means is disposed after the radiator 102, and a branching section 203 is disposed thereafter. In the branch portion 203, the intermediate pressure inlet side path 253 toward the first expansion valve 104 and the low pressure inlet side path 254 toward the second internal heat exchanger 125 are divided.

  In FIG. 2, the high-temperature, high-pressure, supercritical refrigerant sent out from the discharge port 150 of the injection compressor 101 is cooled by the radiator 102, cooled by the first internal heat exchanger 226, and then branched. In 203, the refrigerant is divided into a refrigerant directed to the first expansion valve 104 and a refrigerant directed to the second internal heat exchanger 125. The operation and control of the refrigerant flowing from the branching section 203 to the first expansion valve 104 and the refrigerant going to the second internal heat exchanger 125 are the same as those in the first embodiment.

  As an effect of changing the arrangement of the first internal heat exchanger 226, the flow rate of the refrigerant cooled in the first internal heat exchanger 226 increases, so that the first state is the same if the state of the refrigerant after the radiator 102 is the same. Compared to the embodiment, the average temperature of the refrigerant to be cooled is increased, and the ability to heat the refrigerant flowing from the second internal heat exchanger 125 and prevent liquid return to the intermediate pressure inlet 151 is excellent. .

  As described above, the refrigeration cycle apparatus according to the present invention includes the first internal heat exchanger 126 or 226 (FIG. 2), the second internal heat exchanger 125, the first expansion valve 104, and the flow control valve 141. By controlling the second internal heat exchanger 125 and the first expansion valve 104, liquid return to the intermediate pressure inlet 151 can be prevented, and a highly reliable device can be provided.

  In addition, the refrigeration cycle apparatus according to the present invention has a first internal heat exchanger 126 and a second internal heat exchanger 125 after the branching portion 103 as shown in FIG. A highly efficient operation can be performed by reducing the compression power.

  Further, as shown in FIG. 2, the refrigeration cycle apparatus according to the present invention cools the refrigerant from the radiator 102 by the first internal heat exchanger 226, and then supplies the refrigerant and the refrigerant directed to the first expansion valve 104 at the branch portion 203. By disposing the refrigerant so as to be divided into the two refrigerants directed to the internal heat exchanger 125, it is possible to provide an apparatus having an excellent ability to prevent liquid return to the intermediate pressure inlet 151.

  The refrigeration cycle apparatus according to the present invention includes an evaporation temperature sensor 143, a first pipe temperature sensor 112, and a second pipe temperature sensor 142 as shown in FIGS. 1 and 2, and based on the temperature information. By controlling the 1 expansion valve 104 and the flow control valve 141, an inexpensive apparatus can be provided without using an expensive pressure sensor.

  1 and 2, the refrigeration cycle apparatus according to the present invention controls the first expansion valve 104 based on the difference between the temperature detected by the evaporation temperature sensor 143 and the temperature detected by the first pipe temperature sensor 112. By controlling the flow rate control valve 141 based on the difference between the temperature detected by the evaporation temperature sensor 143 and the temperature detected by the second pipe temperature sensor 142, highly reliable control can be performed with a simple control algorithm. .

  In the refrigeration cycle apparatus of the present invention, a bypass path having a flow rate control valve is provided between the second heat exchange means and the first heat exchange means in the refrigerant path exiting the first decompression means, The pressure reducing means and the flow rate control valve are controlled by comparing the detected temperature of the evaporating temperature detecting means with the detected temperatures of the first refrigerant temperature detecting means and the second refrigerant temperature detecting means, and the intermediate pressure suction of the injection compressor The liquid return to the mouth is prevented and is particularly effective for an air conditioner or a refrigeration apparatus using a carbon dioxide refrigerant, but can also be applied to a heat pump hot water supply apparatus or the like. Moreover, it has an effect also in the apparatus using refrigerants other than carbon dioxide.

Configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. The block diagram of the refrigerating-cycle apparatus in Embodiment 2 of this invention. Configuration diagram of refrigeration cycle equipment using conventional technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Injection compressor 102 Radiator 103,203 Branch part 104 1st expansion valve 106 2nd expansion valve 107 Heat absorber 110 Injection circuit control apparatus 112 1st piping temperature sensor 125 2nd heat exchanger 126,226 1st heat exchanger 141 Flow control valve 142 Second piping temperature sensor 143 Evaporation temperature sensor 151 Intermediate pressure inlet 152 Low pressure inlet 153,253 Intermediate pressure inlet side path 154,254 Low pressure inlet side path

Claims (5)

An injection compressor having a low-pressure inlet and an intermediate-pressure inlet, compressing the refrigerant and sending out the high-temperature and high-pressure refrigerant, a heat radiating means for releasing the heat of the high-temperature and high-pressure refrigerant, and the injected high-pressure refrigerant into the injection compression A branch part for branching into a low pressure inlet side path and an intermediate pressure inlet side path of the machine, and a first pressure reducing means for decompressing and expanding high pressure refrigerant to an intermediate pressure in the intermediate pressure inlet side path; First and second heat exchange means for exchanging heat between the refrigerant evaporating at an intermediate pressure in the intermediate pressure inlet side path and the high-pressure refrigerant radiated by the heat radiating means; and the two heat exchanges A second decompression means for decompressing and expanding the high-pressure refrigerant heat-exchanged by the means to a low pressure, a heat-absorbing means by the low-pressure refrigerant after the second decompression means, and the second passage in the intermediate pressure inlet side path A flow control valve after the heat exchange means And a bypass path for bypassing the first heat exchange means Te,
The refrigerant that has exited the first pressure reducing means of the intermediate pressure inlet side path flows from the second heat exchanging means to the first heat exchanging means, and also passes through the bypass path, the refrigerant of the injection compressor. It is configured to be guided to the intermediate pressure inlet,
The other high-pressure refrigerant cooled by the first heat exchanging means and the second heat exchanging means passes through the second pressure reducing means and the heat absorbing means, and the low pressure suction of the injection compressor. The composition is guided to the mouth,
The intermediate pressure suction side path includes injection circuit control means for controlling the state of refrigerant sucked into the intermediate pressure suction port by adjusting the first pressure reducing means and the flow rate control valve. A refrigeration cycle device. 2. The refrigeration cycle apparatus according to claim 1, wherein the branch portion is disposed in front of the first heat exchange means. 2. The refrigeration cycle apparatus according to claim 1, wherein the branch portion is disposed between the first heat exchange means and the second heat exchange means. In the intermediate pressure inlet side path, the evaporating temperature detecting means for detecting the evaporating temperature of the refrigerant in the second heat exchanging means, and the first refrigerant temperature detecting for detecting the temperature of the refrigerant at the outlet of the second heat exchanging means. And a second refrigerant temperature detecting means for detecting the temperature of the refrigerant before the intermediate pressure inlet, and the injection circuit control means includes the evaporating temperature detecting means, the first refrigerant temperature detecting means, and the second refrigerant temperature detecting means. 4. The refrigeration cycle apparatus according to claim 1, wherein the first pressure reducing means and the flow rate control valve are controlled based on temperature information from the refrigerant temperature detecting means. The injection circuit control means compares the detected temperature of the evaporating temperature detecting means with the detected temperature of the first refrigerant temperature detecting means and operates the first pressure reducing means so that the temperature difference becomes a predetermined value. The flow rate control valve is operated so that the temperature difference between the detected temperature of the evaporating temperature detecting means and the detected temperature of the second refrigerant temperature detecting means is compared to a predetermined value. 4. The refrigeration cycle apparatus according to 4.