JP6664478B2 - Binary refrigeration equipment - Google Patents

Description

  The present invention relates to a binary refrigeration apparatus, and more particularly to a binary refrigeration apparatus provided with an auxiliary radiator on a low-stage refrigeration cycle side.

  Conventionally, as a device for performing cooling at a low temperature of minus several tens of degrees, a high-temperature refrigeration cycle which is a refrigeration cycle device for circulating a high-temperature refrigerant, and a low-temperature refrigeration cycle device for circulating a cold-temperature refrigerant. A binary refrigeration system having a refrigeration cycle is used. In the two-way refrigeration system, for example, a cascade condenser configured so that heat can be exchanged between the lower-side condenser in the lower-stage refrigeration cycle and the higher-side evaporator in the higher-stage refrigeration cycle, The original refrigeration cycle and the higher refrigeration cycle are connected.

  In such a two-way refrigeration system, an auxiliary radiator was installed in front of the cascade condenser, and the refrigerant discharged from the low-temperature side compressor was radiated and cooled by the auxiliary radiator to improve operating efficiency. (For example, see Patent Document 1).

Japanese Patent No. 3604973

  However, in the binary refrigeration apparatus described in Patent Document 1, although the operating efficiency can be improved by the auxiliary radiator, when the discharge temperature of the refrigerant discharged from the lower compressor is low, the auxiliary radiator is The difference between the temperature of the refrigerant flowing through the vessel and the temperature of the outside air is reduced. Therefore, in such a binary refrigeration system, the auxiliary radiator cannot be effectively used.

  The present invention has been made in view of the above-described problems in the related art, and has a binary refrigeration apparatus that can improve the amount of heat exchange in an auxiliary radiator while improving the refrigeration capacity in a high-level refrigeration cycle. The purpose is to provide.

The two-stage refrigeration apparatus of the present invention is a high-stage refrigerant that circulates a high-stage refrigerant by connecting a high-stage compressor, a high-stage condenser, a high-stage expansion valve, and a high-stage evaporator with piping. Connect the high-end refrigeration cycle that forms the circuit with the low-end compressor, auxiliary radiator, low-end condenser, low-end expansion valve, and low-end evaporator with piping to circulate the low-end refrigerant A lower-stage refrigeration cycle forming a lower-stage refrigerant circuit, and the higher-stage refrigerant flowing through the higher-stage refrigerant circuit, the lower-stage refrigerant having the higher-stage evaporator and the lower-stage condenser, And a first cascade condenser that performs heat exchange with the lower refrigerant flowing through the lower refrigerant circuit. A branch circuit that branches and returns upstream of the higher-stage expansion valve; and a branch circuit provided in the branch circuit. And the high-stage-side refrigerant, the second cascade condenser for exchanging heat between the low-stage-side refrigerant flowing out from the low-stage-side evaporator, and the outside air temperature sensor for detecting the outside air temperature, the low A discharge temperature sensor for detecting a discharge temperature of the lower refrigerant discharged from the compressor, a flow control valve for adjusting a flow rate of the higher refrigerant flowing into the branch circuit, and the binary refrigeration apparatus A control device for controlling the operation of each device provided in the , the control device, based on the detection result by the outside air temperature sensor and the detection result by the discharge temperature sensor, the opening degree of the flow rate adjustment valve To control .

  As described above, according to the binary refrigeration apparatus of the present invention, the supercooling degree is imparted to the lower refrigerant by using the second cascade condenser, and the lower refrigerant discharged from the lower compressor. By increasing the discharge temperature of the radiator, the amount of heat exchange in the auxiliary radiator can be improved, and the enthalpy on the higher side can be increased to improve the refrigerating capacity on the higher side.

FIG. 2 is a block diagram illustrating an example of a configuration of a binary refrigeration apparatus according to Embodiment 1. FIG. 9 is a block diagram illustrating an example of a configuration of a binary refrigeration apparatus according to Embodiment 2. FIG. 13 is a block diagram illustrating an example of a configuration of a binary refrigeration apparatus according to Embodiment 3. FIG. 14 is a block diagram showing an example of a configuration of a binary refrigeration apparatus according to Embodiment 4.

Embodiment 1 FIG.
Hereinafter, the binary refrigeration apparatus according to Embodiment 1 of the present invention will be described.

[Configuration of binary refrigeration system]
FIG. 1 is a block diagram illustrating an example of a configuration of the binary refrigeration apparatus 1 according to the first embodiment. As shown in FIG. 1, the binary refrigeration system 1 includes a low refrigeration cycle 10, a high refrigeration cycle 20, and a control device 40. The low-stage refrigeration cycle 10 and the high-stage refrigeration cycle 20 each constitute a refrigerant circuit that circulates refrigerant independently. Further, in the two-stage refrigeration apparatus 1, in order to configure two refrigerant circuits in multiple stages, a lower-stage condenser 13 in a lower-stage refrigeration cycle 10 described later and a higher-stage evaporator 24 in a higher-stage refrigeration cycle 20 are provided. Are provided so as to exchange heat between the refrigerants passing therethrough.

  In addition, the arrow in FIG. 1 shows the direction in which the refrigerant flows. This is the same in FIGS. 2 to 4 described later. Further, in the following description, expressions of height including temperature, pressure, and the like are not determined particularly in relation to absolute values, but are relatively determined by states, operations, and the like in systems, devices, and the like. And

(Lower refrigeration cycle)
The lower refrigeration cycle 10 includes a lower compressor 11, an auxiliary radiator 12, a lower condenser 13, a lower expansion valve 14, and a lower evaporator 15. The low-stage refrigeration cycle 10 forms a low-stage refrigerant circuit in which the low-stage refrigerant circulates by sequentially connecting these devices in a ring via a refrigerant pipe.

  The low-stage compressor 11 draws low-temperature, low-pressure low-stage refrigerant, compresses the refrigerant, and discharges the refrigerant to a high-temperature, high-pressure state. As the lower compressor 11, for example, an inverter compressor or the like capable of controlling the rotation speed by an inverter circuit or the like and capable of controlling the capacity can be used.

  The auxiliary radiator 12 exchanges heat between the lower refrigerant discharged from the lower compressor 11 and outside air such as outdoor air. That is, the auxiliary radiator 12 is a heat exchanger that heats the outside air by releasing heat from the low-source-side refrigerant to the outside air. The auxiliary radiator 12 functions as, for example, a gas cooler and exchanges heat with outside air, water, brine, and the like.

  The low-side condenser 13 condenses and liquefies the low-side refrigerant that has passed through the auxiliary radiator 12, and turns it into a liquid refrigerant. In the first embodiment, for example, in the first cascade condenser 30, the lower condenser 13 is configured by a heat transfer tube or the like through which the lower refrigerant flowing through the lower refrigeration cycle 10 passes, and the lower refrigerant is higher. It is assumed that heat exchange is performed with the refrigerant flowing through the refrigeration cycle 20.

  The lower expansion valve 14 is configured to reduce the pressure and expand the flow by adjusting the flow rate of the lower refrigerant that has passed through the lower condenser 13. As the lower expansion valve 14, for example, a flow control means such as an electronic expansion valve, a capillary such as a capillary, and a refrigerant flow control means such as a temperature-sensitive expansion valve can be used.

  The lower evaporator 15 exchanges heat between the lower refrigerant decompressed by the lower expansion valve 14 and room air such as air in a freezing room to be cooled, and converts the lower refrigerant to the lower refrigerant. It evaporates to a gaseous refrigerant. Due to the heat exchange with the low element side refrigerant, the object to be cooled is cooled directly or indirectly.

(Takamoto refrigeration cycle)
The high-stage refrigeration cycle 20 includes a high-stage compressor 21, a high-stage condenser 22, a high-stage expansion valve 23, and a high-stage evaporator 24. The high-end refrigeration cycle 20 forms a high-end refrigerant circuit in which the high-end refrigerant circulates by sequentially connecting these devices in a ring via a refrigerant pipe.

  In the high-stage refrigeration cycle 20, a branch circuit 20a in which a refrigerant pipe branches is formed between the high-side condenser 22 and the high-side expansion valve 23. The branch circuit 20 a is formed so as to branch from the downstream side of the high-side condenser 22 and return to the upstream side of the high-side expansion valve 23. The branch circuit 20a is provided with a second cascade capacitor 26.

  The high-stage compressor 21 draws in a low-temperature and low-pressure high-stage refrigerant, compresses the refrigerant, and discharges the refrigerant to a high-temperature and high-pressure state. As the high compressor 21, for example, an inverter compressor or the like that can control the number of revolutions by an inverter circuit or the like and can control the capacity can be used.

  The high-side condenser 22 exchanges heat between the high-side refrigerant discharged from the high-side compressor 21 and the outside air such as outdoor air to condense and liquefy the refrigerant into a liquid refrigerant. Things. That is, the higher condenser 22 is a heat exchanger that heats the outside air by releasing heat from the higher refrigerant to the outside air. The high-side condenser 22 functions as, for example, a gas cooler, and exchanges heat with outside air, water, brine, and the like. The high side condenser 22 is provided with a fan 25 for promoting heat exchange. As such a fan 25, for example, a fan whose air volume can be adjusted can be used.

  The high-stage expansion valve 23 is a decompression device, a throttle device, or the like, and adjusts the flow rate of the high-stage refrigerant passing through the high-stage condenser 22 to reduce the pressure and expand the refrigerant. As the high-side expansion valve 23, for example, a flow control means such as an electronic expansion valve, a capillary such as a capillary, a refrigerant flow control means such as a temperature-sensitive expansion valve, or the like can be used.

  The high-side evaporator 24 performs heat exchange between the high-side refrigerant decompressed by the high-side expansion valve 23 and the low-side refrigerant that has passed through the auxiliary radiator 12 of the low-stage refrigeration cycle 10, The high-end-side refrigerant is evaporated to a low-temperature gaseous refrigerant. In the first embodiment, for example, in the first cascade condenser 30, the higher-side evaporator 24 is constituted by a heat transfer tube or the like through which the higher-side refrigerant flowing through the higher-stage refrigeration cycle 20 passes, and It is assumed that heat exchange is performed with the lower refrigerant flowing through the refrigeration cycle 10.

  The second cascade condenser 26 includes a medium-temperature / high-pressure liquid high-side refrigerant condensed and liquefied in the high-side condenser 22 and a low-temperature / low-pressure gaseous low-side refrigerant sucked into the low-side compressor 11. Heat exchange between Here, it is assumed that the temperature of the high-side refrigerant condensed and liquefied in the high-side condenser 22 is higher than the temperature of the low-side refrigerant sucked into the low-side compressor 11.

  By performing heat exchange by the second cascade condenser 26, the higher-stage refrigerant becomes a liquid refrigerant with a degree of supercooling, and flows into the higher-stage expansion valve 23 through the branch circuit 20a. The low-stage-side refrigerant becomes a gas refrigerant having a degree of superheat, and is sucked into the low-stage-side compressor 11.

(Cascade capacitor)
The first cascade condenser 30 is an inter-refrigerant heat exchanger that exchanges heat between the lower refrigerant flowing through the lower condenser 13 and the higher refrigerant flowing through the higher evaporator 24. At this time, the first cascade condenser 30 functions as the lower-side condenser 13 and also functions as the higher-side evaporator 24. By making the lower refrigerant circuit in the lower refrigeration cycle 10 and the higher refrigerant circuit in the higher refrigeration cycle 20 into a multi-stage configuration via the first cascade condenser 30, and performing heat exchange between the refrigerants, Independent refrigerant circuits can be linked.

(Control device)
The control device 40 is configured by software executed on an arithmetic device such as a microcomputer and a CPU (Central Processing Unit), and hardware such as a circuit device for realizing various functions, and the like. Control the operation. For example, the control device 40 may control the low-side compressor 11 and the high-side compressor 21 based on the operation information of the binary refrigeration system 1 based on the information received from the various detection units and the operation content instructed by the user. , The number of rotations including ON / OFF of the fan 25, and the opening degrees of the lower expansion valve 14 and the higher expansion valve 23 are controlled.

  The outside air temperature sensor 41 is connected to the control device 40. The outside air temperature sensor 41 is provided to detect the temperature of outside air such as outdoor air. The outside air temperature sensor 41 supplies the detected outside air temperature to the control device 40.

[Refrigerant circulating in each refrigeration cycle]
In the binary refrigeration apparatus 1 configured as described above, some of the components of the lower refrigeration cycle 10, such as the lower evaporator 15, are provided in an indoor load device such as a supermarket showcase.

  For example, when the connection position of the piping is changed by rearranging or exchanging the showcase, the refrigerant circuit is opened on site. In such a case, the brazing of the refrigerant pipes is performed at a plurality of locations by a contractor on site. Therefore, refrigerant leakage may occur from the brazed portion.

  In addition, in addition to the pipe connection being carried out on site, the length of the refrigerant pipe connected to the low-side refrigeration device that is assumed to be placed outdoors in a normal-sized supermarket or refrigeration warehouse is: For example, it may reach about 100 m. As a result, the number of locations where piping is connected on site further increases, so that the possibility of refrigerant leakage from the piping connection portion increases. On the other hand, in large-scale supermarkets and freezer warehouses, the length of the refrigerant pipe may be 100 m or more. For this reason, the possibility of occurrence of refrigerant leakage is further increased.

  Furthermore, the refrigerant piping constructed on site may be placed in various environmental locations. For example, in a refrigerated warehouse, it is conceivable that the warehouse is placed in a corrosive environment due to corrosive gas generated from stored items. The corrosion of copper by a corrosive atmosphere generally includes nest-like corrosion caused by carboxylic acid such as acetic acid, stress corrosion cracking caused by ammonia or the like, and corrosion caused by acid such as sulfur dioxide gas.

  Also, even when the refrigerant pipe connected to the low-side refrigeration unit is placed outside the room, sulfur-based gas such as hydrogen sulfide may be placed outside the room, for example, near a hot spring, or around a food factory that manufactures processed products such as eggs. It is conceivable that the corrosion of the copper tube due to the sulfur-based material may occur even in a place where cracks occur.

  Usually, in such a refrigeration system, a specification in which anti-corrosion coating is applied to the heat exchanger and piping around the heat exchanger is set. It can be selected in advance. However, when installing piping on site, there is no anticorrosion specification, so it may be difficult to deal with corrosive environments.

Therefore, in the first embodiment, carbon dioxide (CO ₂ ) having a small global warming potential (GWP), which indicates an influence on global warming, is used as the lower refrigerant circulating in the lower refrigeration cycle 10. Or a mixed refrigerant containing CO ₂ is used.

Examples of the high-side refrigerant circulating in the high-end refrigeration cycle 20 include HFO (hydrofluoroolefin) refrigerants such as HFO1234yf and HFO1234ze, and refrigerants having a small effect on global warming, such as CO ₂ , ammonia, and water. Alternatively, it is preferable to use a mixed refrigerant containing any of these. However, in the high-end refrigeration cycle 20, since the high-end side refrigerant circuit is not opened on site, for example, HFC (hydrofluorocarbon) refrigerant such as R32, R404A, R407C, R410A, HFC134a, earth such as propane, isobutane, etc. A refrigerant having a high global warming coefficient or a mixed refrigerant containing any of these may be used.

  As described above, it is preferable to use different refrigerants for the lower refrigerant circulating in the lower refrigeration cycle 10 and the higher refrigerant circulating in the higher refrigeration cycle 20. Further, it is more preferable to use a refrigerant having higher efficiency than the lower refrigerant circulating in the lower refrigeration cycle 10 as the higher refrigerant circulating in the higher refrigeration cycle 20.

[Operation of binary refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to Embodiment 1 will be described. Here, the operation and the like of each component device in the higher refrigerant circuit and the lower refrigerant circuit will be described based on the flow of the refrigerant flowing in each refrigerant circuit.

(Operation of the Yuan refrigeration cycle)
First, the operation of the high-end refrigeration cycle 20 will be described. The high-stage compressor 21 draws in the high-stage refrigerant, compresses the refrigerant, and discharges the refrigerant in a state of high temperature and high pressure. The discharged higher-side refrigerant flows into the higher-side condenser 22. The high-side condenser 22 exchanges heat between the outside air supplied by driving the fan 25 and the high-side refrigerant, and condenses and liquefies the high-side refrigerant.

  The condensed and liquefied higher-stage refrigerant passes through the higher-stage expansion valve 23. The high-side expansion valve 23 reduces the pressure of the high-side refrigerant condensed and liquefied. The depressurized high-side refrigerant flows into the high-side evaporator 24. The high-side evaporator 24 performs heat exchange between the reduced-pressure high-side refrigerant and the low-side refrigerant passing through the low-side condenser 13 by the first cascade condenser 30, Is evaporated and gasified. The high-pressure side refrigerant that has been vaporized and gasified is sucked into the high-pressure side compressor 21.

  The higher refrigerant condensed and liquefied by the higher condenser 22 flows through the branch circuit 20a and also flows into the second cascade condenser 26. The second cascade condenser 26 performs heat exchange between the condensed and liquefied high-side refrigerant and the low-side refrigerant evaporated and gasified by the low-side evaporator 15 to reduce the degree of supercooling to the high-side refrigerant. Give. When the supercooling degree is given to the higher refrigerant, the enthalpy in the higher refrigerant circuit becomes larger as compared with the case where the supercooling degree is not added. The higher refrigerant to which the degree of supercooling is given flows through the branch circuit 20 a and passes through the higher expansion valve 23.

(Operation of the lower refrigeration cycle)
Next, the operation of the lower refrigeration cycle 10 will be described. The low-stage compressor 11 sucks in the low-stage refrigerant and compresses the refrigerant to discharge it at a high temperature and high pressure. The discharged lower element-side refrigerant flows into the auxiliary radiator 12. The auxiliary radiator 12 performs heat exchange between the outside air and the low element side refrigerant. The lower refrigerant flowing through the auxiliary radiator 12 flows into the lower condenser 13.

  The lower condenser 13 performs heat exchange between the inflowing lower refrigerant and the higher refrigerant passing through the higher evaporator 24 by the first cascade condenser 30, and the lower refrigerant Is condensed and liquefied. The condensed and liquefied lower refrigerant flows through the lower expansion valve 14. The lower expansion valve 14 reduces the pressure of the condensed and liquefied lower refrigerant. The decompressed lower-side refrigerant flows into the lower-side evaporator 15.

  The lower element side evaporator 15 performs heat exchange between the decompressed lower element side refrigerant and the object to be cooled, and evaporates and gasifies the lower element side refrigerant. The low-pressure side refrigerant that has been vaporized and gasified passes through the second cascade condenser 26. The second cascade condenser 26 performs heat exchange between the low-pressure side refrigerant that has been vaporized and gasified and the high-pressure side refrigerant that has been condensed and liquefied, and imparts a degree of superheat to the low-level refrigerant. The low-side refrigerant to which the degree of superheat is given is sucked into the low-side compressor 11.

  When the degree of superheat is imparted to the low-side refrigerant sucked into the low-side compressor 11 in this manner, the low-side refrigerant showing the discharge temperature of the low-side refrigerant discharged from the low-side compressor 11 The discharge temperature is higher than in the case where the degree of superheat is not provided. Then, in the auxiliary radiator 12, the temperature difference between the temperature of the outside air and the low-source-side refrigerant discharge temperature increases.

  As described above, in the binary refrigeration apparatus 1 according to Embodiment 1, the high-side compressor 21, the high-side condenser 22, the high-side expansion valve 23, and the high-side evaporator 24 are connected by piping. A high-stage refrigeration cycle 20 for connecting and forming a high-stage refrigerant circuit for circulating the high-stage refrigerant, a low-stage compressor 11, an auxiliary radiator 12, a low-stage condenser 13, and a low-stage expansion valve 14. , And the lower-side refrigeration cycle 10 that connects the lower-side evaporator 15 with piping to form a lower-side refrigerant circuit that circulates the lower-side refrigerant, and the higher-side evaporator 24 and the lower-side condenser 13. And a first cascade condenser 30 that exchanges heat between the higher refrigerant flowing in the higher refrigerant circuit and the lower refrigerant flowing in the lower refrigerant circuit. Further, the binary refrigeration apparatus 1 is provided in a branch circuit 20a that branches from the downstream of the higher condenser 22 in the higher refrigeration cycle 20 and returns to the upstream of the higher expansion valve 23; A second cascade condenser 26 for exchanging heat between the higher refrigerant flowing through the circuit 20a and the lower refrigerant flowing out of the lower evaporator 15; And a control device 40 for controlling the operation of.

  As described above, in the second cascade condenser 26, the higher-side refrigerant flowing through the branch circuit 20a and the lower-side refrigerant flowing out of the lower-side evaporator 15 perform heat exchange, so that the higher-side refrigerant Since the temperature is higher than the temperature of the lower refrigerant, the degree of supercooling is given to the higher refrigerant. At the same time, the degree of superheat is given to the lower element side refrigerant.

  Then, since the enthalpy in the higher-stage refrigerant circuit is increased by imparting the degree of supercooling to the higher-stage refrigerant, the refrigeration capacity of the higher-stage refrigerant circuit, that is, the higher-stage refrigeration cycle 20 is improved. Can be. Further, the capacity of the high-stage compressor 21 can be reduced.

  Further, the degree of superheat given to the lower element side refrigerant increases the degree of superheat of the lower element side refrigerant sucked into the lower element side compressor 11. The refrigerant discharge temperature can be increased. As described above, the temperature of the low-side refrigerant flowing into the auxiliary radiator 12 can be made higher than in the related art. Therefore, the temperature difference between the auxiliary radiator 12 and the outside air that performs heat exchange can be increased, the amount of heat exchange in the auxiliary radiator 12 can be improved, and the auxiliary radiator 12 can be used effectively.

Embodiment 2 FIG.
Next, the binary refrigeration apparatus 1 according to Embodiment 2 will be described. The second embodiment is different from the first embodiment in that a flow control valve is provided in the branch circuit 20a of the higher refrigerant circuit.

[Configuration of binary refrigeration system]
FIG. 2 is a block diagram illustrating an example of a configuration of the binary refrigeration apparatus 1 according to Embodiment 2. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 2, the binary refrigeration apparatus 1 includes a low refrigeration cycle 10, a high refrigeration cycle 20, a first cascade condenser 30, and a control device 40, similarly to the first embodiment. A branch circuit 20 a is provided in the high-stage refrigerant circuit of the refrigeration cycle 20.

  In the second embodiment, a flow regulating valve 42 is provided in the branch circuit 20a. A discharge temperature sensor 43 is provided on the discharge side of the lower compressor 11.

  The flow rate adjustment valve 42 is provided to adjust the flow rate of the higher refrigerant flowing into the branch circuit 20a, and the opening thereof is controlled by the control device 40. As the flow control valve 42, for example, a flow control means such as an electronic expansion valve, a capillary tube such as a capillary, and a refrigerant flow control means such as a temperature-sensitive expansion valve can be used.

  When the flow control valve 42 is opened, the flow rate of the high-side refrigerant exchanged by the second cascade condenser 26 increases, and the degree of superheating of the low-side refrigerant sucked into the low-side compressor 11 increases. Therefore, the temperature of the low-side refrigerant discharged from the low-side compressor 11 increases.

  On the other hand, when the flow control valve 42 is closed, the flow rate of the high-side refrigerant exchanged by the second cascade condenser 26 decreases, and the degree of superheat of the low-side refrigerant sucked into the low-side compressor 11 decreases. . Therefore, the temperature of the low-side refrigerant discharged from the low-side compressor 11 decreases.

  The discharge temperature sensor 43 is provided for detecting a low-side refrigerant discharge temperature in the low-side compressor 11. The discharge temperature sensor 43 supplies information indicating the detected low-side refrigerant discharge temperature to the control device 40.

  The controller 40 further controls the flow rate based on the outside air temperature supplied from the outside air temperature sensor 41 and the low-side refrigerant discharge temperature supplied from the discharge temperature sensor 43 in addition to the operation described in the first embodiment. The opening of the regulating valve 42 is controlled.

[Operation of binary refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to Embodiment 2 will be described. In the following description, a detailed description of the same operations as those in the first embodiment will be omitted. Further, the low-stage refrigeration cycle 10 is the same as that in the first embodiment, and therefore, the description is omitted.

(Operation of the Yuan refrigeration cycle)
In the second embodiment, the operation from when the higher refrigerant is sucked into the higher compressor 21 until it is condensed and liquefied in the higher condenser 22 is the same as that in the first embodiment. Therefore, the description is omitted.

  When the temperature of the low-side refrigerant discharged from the low-side compressor 11 is low, the flow control valve 42 is opened, and in this case, the high-level refrigerant condensed and liquefied by the high-side condenser 22. The side refrigerant passes through the high-side expansion valve 23 and also flows into the branch circuit 20a. The higher refrigerant flowing into the branch circuit 20a flows into the second cascade condenser 26, and exchanges heat with the lower refrigerant vaporized by the lower evaporator 15. Thereby, the supercooling degree is given to the high element side refrigerant. The higher refrigerant to which the degree of supercooling is given flows through the branch circuit 20 a and passes through the higher expansion valve 23.

  On the other hand, when the temperature of the low-side refrigerant discharged from the low-side compressor 11 is high, the flow control valve 42 is set to the “closed” state, and in this case, the refrigerant is condensed and liquefied by the high-side condenser 22. The higher refrigerant does not flow into the branch circuit 20a but passes through the higher expansion valve 23. The high-side refrigerant passing through the high-side expansion valve 23 is decompressed and flows into the high-side evaporator 24. The higher refrigerant flowing into the higher evaporator 24 exchanges heat with the lower refrigerant passing through the lower condenser 13 by the first cascade condenser 30 to evaporate and gasify. Is done. Then, the evaporative gasified high-stage refrigerant is sucked into the high-stage compressor 21.

Here, the amount of heat exchange in the heat exchanger will be described. The heat exchange amount Q [W] indicating the capacity of the heat exchanger can be generally represented by Expression (1). In the equation (1), “K” indicates the heat transfer rate [W / m ² · K] of the heat exchanger, and is determined by the specification of the heat exchanger and, in the case of the air heat exchanger, the combined air volume. Is done. “A” indicates the heat transfer area [m ² ] of the heat exchanger, and is determined by the area of the heat exchanger. “ΔT _m ” indicates an average temperature difference [K] between two media that perform heat exchange.

[Equation 1]
Q = K × A × ΔT _m (1)

In this case, for example, heat transfer coefficient K and the heat transfer area A is always assumed to take the same value, by increasing the average temperature difference [Delta] T _m, it is possible to increase the heat exchange amount Q. That is, by increasing the temperature of the refrigerant flowing into the heat exchanger, the average temperature difference ΔT _m can be increased, so that the heat exchange amount Q can be increased.

  Therefore, in the second embodiment, by controlling the opening degree of the flow control valve 42, it is possible to increase the discharge temperature of the low-side refrigerant in the low-side compressor 11; The temperature of the lower element side refrigerant flowing into the auxiliary radiator 12 increases, and the amount of heat exchange in the auxiliary radiator 12 can be increased.

Here, control for improving the refrigeration capacity in the low-stage refrigeration cycle 10 and the high-stage refrigeration cycle 20 will be described. For example, a case is considered in which the opening degree of the lower expansion valve 14 is increased based on the control by the controller 40, and the lower refrigerant flowing out of the lower evaporator 15 is in a gas-liquid two-phase state. . In this case, since all the lower refrigerants in the lower evaporator 15 are in the gas-liquid two-phase state, the lower refrigerant in the gas-liquid two-phase state and the object to be cooled, such as air in the refrigerator, may be used. Performs heat exchange. Thus, an average temperature difference [Delta] T _m of the low-stage-side refrigerant is shown in Equation (1) described above and the cooling target can be larger than the normal state. Therefore, since the heat exchange amount Q in the lower evaporator 15 can be increased, the cooling capacity of the lower refrigeration cycle 10 can be improved.

  In addition, the amount of heat exchange in the second cascade condenser 26 that performs heat exchange between the lower refrigerant flowing out of the lower evaporator 15 and the higher refrigerant flowing through the branch circuit 20a also increases. Therefore, the degree of supercooling given to the high-stage refrigerant can be increased, and the enthalpy in the high-stage refrigerant circuit increases, so that the refrigerating capacity of the high-stage refrigeration cycle 20 can be improved.

  As described above, the binary refrigeration apparatus 1 according to Embodiment 2 detects the outside air temperature sensor 41 that detects the temperature of the outside air and the discharge temperature of the low-side refrigerant discharged from the low-side compressor 11. And a flow rate adjusting valve 42 for adjusting the flow rate of the high-side refrigerant flowing into the branch circuit 20a. The control device 40 detects the detection result of the outside air temperature sensor 41 and the detection result of the discharge temperature sensor 43. Based on the detection result, the opening of the flow control valve 42 is controlled.

  As described above, in the second embodiment, the opening degree of the flow control valve 42 is controlled based on the low-side refrigerant discharge temperature detected by the discharge temperature sensor 43 and the outside air temperature detected by the outside air temperature sensor 41. I do. Therefore, the temperature difference between the low-temperature side refrigerant discharge temperature flowing into the auxiliary radiator 12 and the outside air temperature can be increased, and the auxiliary radiator 12 can be effectively used as in the first embodiment. Thus, even when the low-side refrigerant discharge temperature in the low-side compressor 11 is hard to rise and the evaporation temperature of the low-side evaporator 15 is high, the cooling performance of the low-side refrigerant circuit is ensured. be able to.

  In general, an upper limit is set for the discharge temperature of the compressor in order to prevent a malfunction such as a failure of the compressor. In the second embodiment, by controlling the opening degree of the flow control valve 42, the temperature of the low-side refrigerant sucked into the low-side compressor 11 is adjusted, and the low-side refrigerant in the low-side compressor 11 is adjusted. The refrigerant discharge temperature can be adjusted. Therefore, it is possible to prevent problems of the low-stage compressor 11 due to an increase in the discharge temperature of the low-stage refrigerant, and to prolong the life of the low-stage compressor 11.

Embodiment 3 FIG.
Next, the binary refrigeration apparatus 1 according to Embodiment 3 will be described. Embodiment 3 is characterized in that a low-side injection circuit that connects between the low-side condenser and the low-side expansion valve and between the low-side evaporator and the low-side compressor is provided. This is different from the second embodiment.

[Configuration of binary refrigeration system]
FIG. 3 is a block diagram illustrating an example of a configuration of the binary refrigeration apparatus 1 according to Embodiment 3. In the following description, portions common to the above-described first and second embodiments are denoted by the same reference numerals, and detailed description is omitted. As shown in FIG. 3, the binary refrigeration apparatus 1 includes a lower refrigeration cycle 10, a higher refrigeration cycle 20 provided with a branch circuit 20 a, a first cascade condenser 30, and a control device, as in the second embodiment. 40.

  In the third embodiment, a lower injection circuit 10 a is formed in the lower refrigerant circuit of the lower refrigeration cycle 10. The lower injection circuit 10 a is a branch circuit that connects between the lower condenser 13 and the lower expansion valve 14 and between the lower evaporator 15 and the lower compressor 11. The lower injection circuit 10a is provided with an injection expansion valve 51.

  The injection expansion valve 51 is provided for adjusting the flow rate of the lower refrigerant flowing into the lower injection circuit 10a, and the opening thereof is controlled by the controller 40. As the injection expansion valve 51, for example, a flow control means such as an electronic expansion valve, a capillary such as a capillary, a refrigerant flow control means such as a temperature-sensitive expansion valve, or the like can be used. In the third embodiment, as the injection expansion valve 51, for example, an electronic expansion valve capable of adjusting the low-stage refrigerant discharge temperature in the low-stage compressor 11 can be used.

  The control device 40 controls the opening degree of the injection expansion valve 51 based on the low-side refrigerant discharge temperature in the low-side compressor 11 supplied from the discharge temperature sensor 43.

  The second cascade condenser 26 provided in the lower injection circuit 10a flows through the higher refrigerant flowing in the higher branch circuit 20a and the lower injection circuit 10a, and is throttled by the injection expansion valve 51. Heat exchange is performed between the low-temperature low-pressure gas-liquid two-phase low-temperature side refrigerant.

[Operation of binary refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to Embodiment 3 will be described. In the following description, a detailed description of the same operation as in the above-described first and second embodiments will be omitted. Further, the high-end refrigeration cycle 20 is the same as that of the second embodiment, and thus the description is omitted.

(Operation of the lower refrigeration cycle)
In the third embodiment, the operation from when the lower refrigerant is sucked into the lower compressor 11 to when it is condensed and liquefied by the lower condenser 13 is described in the first and second embodiments. 2, and the description is omitted.

  The low-side refrigerant condensed and liquefied by the low-side condenser 13 passes through the low-side expansion valve 14 and also flows into the low-side injection circuit 10a. The lower refrigerant flowing into the lower injection circuit 10 a passes through the injection expansion valve 51. The injection expansion valve 51 throttles the condensed and liquefied low-side refrigerant, and converts the condensed and liquefied low-side refrigerant into a low-temperature and low-pressure gas-liquid two-phase low-side refrigerant.

  At this time, the low-pressure side refrigerant that has passed through the injection expansion valve 51 and is in a low-temperature low-pressure gas-liquid two-phase state passes through the low-pressure side evaporator 15 and is sucked into the low-pressure side compressor 11. The pressure becomes the same as the pressure of the side refrigerant. This is because the downstream side of the injection expansion valve 51 is connected to the suction side of the low-stage compressor 11.

  The low-side refrigerant that has become the low-temperature low-pressure gas-liquid two-phase refrigerant passes through the second cascade condenser 26. The second cascade condenser 26 performs heat exchange between the lower refrigerant in a gas-liquid two-phase state at a low temperature and a lower pressure and the condensed and liquefied higher refrigerant.

  Here, the low-side refrigerant passing through the second cascade condenser 26 is provided by the low-side evaporator 15 as compared with the low-temperature low-pressure gasified low-side refrigerant that has passed through the low-side evaporator 15. The temperature is lowered by the degree of superheating. This is obtained by adding the degree of superheat given by the lower evaporator 15 to the saturation temperature at which the temperature of the lower refrigerant passing through the lower evaporator 15 is converted from the lower pressure of the lower element. On the other hand, the temperature of the low element side refrigerant that has passed through the injection expansion valve 51 is the saturation temperature converted from the low element side low pressure. Therefore, the temperature difference between the lower refrigerant and the higher refrigerant exchanged in the second cascade condenser 26 is lower than that in the second embodiment, It becomes larger by the degree of superheat given to the original refrigerant.

  Therefore, a higher degree of supercooling is provided to the high-end refrigerant, which is a high-temperature and high-pressure liquid refrigerant that performs heat exchange in the second cascade condenser 26, as compared with the second embodiment. Thereby, in the third embodiment, the enthalpy on the high-end side can be increased, and the refrigeration capacity of the high-end refrigeration cycle 20 can be improved. Thus, a compressor having a small capacity can be used as the high-side compressor 21.

  As described above, the binary refrigeration apparatus 1 according to Embodiment 3 includes the components between the low-side condenser 13 and the low-side expansion valve 14 and the low-side evaporator 15 and the low-side compressor 11. The control device 40 further includes a lower injection circuit 10a for connecting the air conditioner and an injection expansion valve 51 provided in the lower injection circuit 10a. The opening degree of 51 is controlled.

  Accordingly, the temperature difference between the lower refrigerant and the higher refrigerant that perform heat exchange in the second cascade condenser 26 can be made larger than in the first and second embodiments. The refrigeration capacity of the high-order refrigeration cycle 20 can be further improved.

Embodiment 4 FIG.
Next, a binary refrigeration apparatus 1 according to Embodiment 4 will be described. The fourth embodiment differs from the third embodiment in that a suction temperature sensor for detecting the temperature of the low-side refrigerant drawn into the suction side of the low-side compressor 11 is provided.

[Configuration of binary refrigeration system]
FIG. 4 is a block diagram illustrating an example of a configuration of the binary refrigeration apparatus 1 according to Embodiment 4. In the following description, the same parts as those in the first to third embodiments are denoted by the same reference numerals, and detailed description will be omitted. As shown in FIG. 4, the binary refrigeration apparatus 1 includes a lower refrigeration cycle 10 provided with a lower injection circuit 10 a and a higher refrigeration cycle 20 provided with a branch circuit 20 a, similarly to the third embodiment. , The first cascade capacitor 30 and the control device 40.

  In the fourth embodiment, a suction temperature sensor 44 is provided on the suction side of the lower compressor 11. The suction temperature sensor 44 is provided for detecting a low-side refrigerant suction temperature indicating the suction temperature of the low-side refrigerant sucked into the low-side compressor 11. The suction temperature sensor 44 supplies the controller 40 with information indicating the detected lower-stage refrigerant suction temperature.

  The control device 40 further includes, in addition to the operations described in the first to third embodiments, the outside air temperature supplied from the outside air temperature sensor 41, the lower element-side refrigerant discharge temperature supplied from the discharge temperature sensor 43, The opening degree of the injection expansion valve 51 is controlled based on the low-side refrigerant suction temperature supplied from the temperature sensor 44.

  For example, the control device 40 controls the opening degree of the injection expansion valve 51 based on the detected lower-stage refrigerant discharge temperature and the detected lower-stage refrigerant suction temperature so as to balance both temperatures. In addition, the control device 40 considers the detected outside air temperature, and in the auxiliary radiator 12, the temperature of the high-temperature and high-pressure gasified low-side refrigerant discharged from the low-side compressor 11 and the temperature of the outside air. The opening degree of the injection expansion valve 51 is controlled so as to secure the difference.

  As described above, the binary refrigeration apparatus 1 according to Embodiment 4 further includes the suction temperature sensor 44 that detects the suction temperature of the low-side refrigerant sucked into the low-side compressor 11, and the control device 40 Controls the opening degree of the injection expansion valve 51 based on the detection result by the outside air temperature sensor 41, the detection result by the discharge temperature sensor 43, and the detection result by the suction temperature sensor 44. Thereby, the operating range of the lower compressor 11 can be secured, and problems such as failure of the lower compressor 11 can be prevented.

  As described above, the first to fourth embodiments of the present invention have been described. However, the present invention is not limited to the above-described first to fourth embodiments of the present invention. Various modifications and applications are possible without departing from the scope.

  DESCRIPTION OF SYMBOLS 1 Binary refrigeration system, 10 Refrigeration cycle, 10a Bottom side injection circuit, 11 Bottom side compressor, 12 Auxiliary radiator, 13 Bottom side condenser, 14 Bottom side expansion valve, 15 Bottom side evaporation 20 high-end refrigeration cycle, 20a branch circuit, 21 high-end compressor, 22 high-end condenser, 23 high-end expansion valve, 24 high-end evaporator, 25 fan, 26 second cascade condenser, 30 first cascade condenser, 40 control device, 41 outside air temperature sensor, 42 flow control valve, 43 discharge temperature sensor, 44 suction temperature sensor, 51 injection expansion valve.

Claims (8)

A high-end refrigeration cycle that connects a high-end compressor, a high-end condenser, a high-end expansion valve, and a high-end evaporator with piping to form a high-end refrigerant circuit that circulates the high-end refrigerant. ,
The low-side compressor, the auxiliary radiator, the low-side condenser, the low-side expansion valve, and the low-side evaporator are connected by piping to form a low-side refrigerant circuit that circulates the low-side refrigerant. Former refrigeration cycle,
Having the higher-side evaporator and the lower-side condenser, heat is generated between the higher-side refrigerant flowing through the higher-side refrigerant circuit and the lower-side refrigerant flowing through the lower-side refrigerant circuit. A binary refrigeration system comprising a first cascade condenser for replacement.
A branch circuit that branches from the downstream of the higher condenser in the higher refrigeration cycle and returns upstream of the higher expansion valve;
A second cascade condenser that is provided in the branch circuit and exchanges heat between the higher refrigerant flowing through the branch circuit and the lower refrigerant flowing out of the lower evaporator;
An outside air temperature sensor that detects an outside air temperature;
A discharge temperature sensor that detects a discharge temperature of the low-side refrigerant discharged from the low-side compressor,
A flow control valve that adjusts the flow rate of the higher refrigerant flowing into the branch circuit,
A control device for controlling the operation of each device provided in the binary refrigeration apparatus,
The control device includes:
A binary refrigeration apparatus that controls an opening degree of the flow control valve based on a detection result by the outside air temperature sensor and a detection result by the discharge temperature sensor. The control device includes:
The two-stage refrigeration apparatus according to claim 1, wherein an opening degree of the lower-stage expansion valve is controlled such that the lower-stage refrigerant flowing out of the lower-stage evaporator is in a gas-liquid two-phase state. An injection circuit that connects between the lower condenser and the lower expansion valve, between the lower evaporator and the lower compressor,
Further comprising an injection expansion valve provided in the injection circuit,
The control device includes:
3. The binary refrigeration apparatus according to claim 1, wherein an opening degree of the injection expansion valve is controlled based on a result detected by the discharge temperature sensor. 4. A suction temperature sensor that detects a suction temperature of the low-stage refrigerant sucked into the low-stage compressor;
The control device includes:
4. The binary refrigeration apparatus according to claim 3, wherein an opening degree of the injection expansion valve is controlled based on a detection result by the outside air temperature sensor, a detection result by the discharge temperature sensor, and a detection result by the suction temperature sensor. 5. In the higher refrigerant and the lower refrigerant,
The binary refrigeration apparatus according to any one of claims 1 to 4, wherein different refrigerants are used. The higher element refrigerant includes:
The binary refrigeration apparatus according to any one of claims 1 to 5, wherein a refrigerant having higher efficiency than the low element side refrigerant is used. At least one of the higher refrigerant and the lower refrigerant,
The binary refrigeration apparatus according to any one of claims 1 to 6, wherein a carbon dioxide refrigerant or a mixed refrigerant containing carbon dioxide is used. At least one of the higher refrigerant and the lower refrigerant,
R32, R410A, R134a, R404A, R407C, HF O 1234yf, HFO1234ze, ammonia, propane, and any one of claims 1 to 7, either a refrigerant or a mixed refrigerant containing any one of these isobutane is used A binary refrigeration device as described.

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