WO2017221382A1

WO2017221382A1 - Binary refrigeration device

Info

Publication number: WO2017221382A1
Application number: PCT/JP2016/068697
Authority: WO
Inventors: 智也藤本; 智隆石川; 悠介有井
Original assignee: 三菱電機株式会社
Priority date: 2016-06-23
Filing date: 2016-06-23
Publication date: 2017-12-28
Also published as: JPWO2017221382A1; GB2565472A; GB2565472B; GB201818273D0; JP6664478B2

Abstract

A binary refrigeration device comprising: a high-order refrigeration cycle in which a high-order side compressor, a high-order side condenser, a high-order side expansion valve, and a high-order side evaporator are connected by piping and that forms a high-order side refrigerant circuit in which a high-order side refrigerant circulates; a low-order refrigeration cycle in which a low-order side compressor, an auxiliary radiator, a low-order side condenser, a low-order side expansion valve, and a low-order side evaporator are connected by piping and that forms a low-order side refrigerant circuit in which a low-order side refrigerant circulates; and a first cascade condenser that has the high-order side evaporator and the low-order side condenser and that performs heat exchange between the high-order side refrigerant that flows in the high-order side refrigerant circuit and the low-order side refrigerant that flows in the low-order side refrigerant circuit. The binary refrigeration device comprises: a branch circuit that branches from the downstream side of the high-order side condenser in the high-order refrigeration cycle and that returns to the upstream side of the high-order side expansion valve; a second cascade condenser that is provided in the branch circuit and that performs heat exchange between the high-order side refrigerant that flows in the branch circuit and the low-order side refrigerant flowing from the low-order side evaporator; and a control device that controls the operation of each apparatus provided in the binary refrigeration device.

Description

Dual refrigeration equipment

The present invention relates to a binary refrigeration apparatus, and more particularly to a binary refrigeration apparatus having an auxiliary radiator on the low-source refrigeration cycle side.

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

In such a binary refrigeration system, an auxiliary radiator is installed in front of the cascade condenser, and the refrigerant discharged from the low-temperature side compressor is radiated by the auxiliary radiator to be cooled, thereby improving the operation efficiency. There are some (see, for example, Patent Document 1).

Japanese Patent No. 3606043

However, in the binary refrigeration apparatus described in Patent Document 1, the operation efficiency can be improved by the auxiliary radiator, but if the discharge temperature of the refrigerant discharged from the low-side compressor is low, the auxiliary heat dissipation The difference between the temperature of the refrigerant flowing in the vessel and the outside air temperature is reduced. Therefore, such a binary refrigeration apparatus cannot effectively utilize the auxiliary radiator.

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

The binary refrigeration apparatus of the present invention is a high-side refrigerant that connects a high-side compressor, a high-side condenser, a high-side expansion valve, and a high-side evaporator through piping and circulates the high-side refrigerant. A high-source refrigeration cycle that forms a circuit, and a low-side compressor, auxiliary radiator, low-side condenser, low-side expansion valve, and low-side evaporator are connected by piping to circulate the low-side refrigerant. A low original refrigeration cycle that forms a low original refrigerant circuit, the high original evaporator and the low original condenser, the high original refrigerant flowing through the high original refrigerant circuit, and the low original A two-stage refrigeration apparatus comprising a first cascade condenser that exchanges heat with the low-side refrigerant flowing in the side-side refrigerant circuit, from the downstream of the high-side condenser in the high-source refrigeration cycle A branch circuit that branches and returns to the upstream side of the high-side expansion valve; and the branch circuit provided in the branch circuit. Operation of each device provided in the second cascade condenser that exchanges heat between the flowing high-side refrigerant and the low-side refrigerant flowing out of the low-side evaporator, and the binary refrigeration apparatus And a control device for controlling.

As described above, according to the binary refrigeration apparatus of the present invention, the low-source side refrigerant discharged from the low-side compressor is provided with superheat to the low-side refrigerant using the second cascade condenser. By increasing the discharge temperature, the amount of heat exchange in the auxiliary radiator can be improved, and the high-side enthalpy can be increased to improve the high-side refrigeration capacity.

3 is a block diagram illustrating an example of a configuration of a binary refrigeration apparatus according to Embodiment 1. FIG. It is a block diagram which shows an example of a structure of the binary refrigeration apparatus which concerns on Embodiment 2. FIG. 6 is a block diagram illustrating an example of a configuration of a binary refrigeration apparatus according to Embodiment 3. FIG. It is a block diagram which shows an example of a structure of the binary refrigeration apparatus which concerns on Embodiment 4. FIG.

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

[Configuration of dual refrigeration system]
FIG. 1 is a block diagram illustrating an example of the configuration of the binary refrigeration apparatus 1 according to the first embodiment. As shown in FIG. 1, the binary refrigeration apparatus 1 includes a low original refrigeration cycle 10, a high original refrigeration cycle 20, and a control device 40. The low-source refrigeration cycle 10 and the high-source refrigeration cycle 20 constitute a refrigerant circuit that circulates the refrigerant independently of each other. Further, in the two-stage refrigeration apparatus 1, in order to configure two refrigerant circuits in multiple stages, a low-source side condenser 13 in a low-source refrigeration cycle 10 to be described later, and a high-side evaporator 24 in a high-source refrigeration cycle 20 Are coupled so as to exchange heat between the refrigerants passing through the first cascade capacitor 30.

In addition, the arrow in FIG. 1 shows the direction through which a refrigerant | coolant flows. The same applies to FIGS. 2 to 4 described later. Also, in the following description, the expression of elevation including temperature, pressure, etc. is not particularly defined in relation to absolute values, but is relatively determined by the state, operation, etc. of the system, device, etc. And

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

The low-side compressor 11 sucks low-temperature and low-pressure low-side refrigerant, compresses the refrigerant, and discharges it in a high-temperature and high-pressure state. As the low-source side compressor 11, for example, an inverter compressor that can control the rotation speed by an inverter circuit or the like and can control the capacity can be used.

The auxiliary radiator 12 performs heat exchange between the low-side refrigerant discharged from the low-side compressor 11 and the outside air such as outdoor air. In other words, the auxiliary radiator 12 is a heat exchanger that heats the outside air by releasing heat from the low-side refrigerant to the outside air. The auxiliary radiator 12 functions as a gas cooler, for example, 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 to form a liquid refrigerant. In the first embodiment, for example, in the first cascade condenser 30, the low-side condenser 13 is configured by a heat transfer tube or the like through which the low-side refrigerant flowing through the low-source refrigeration cycle 10 passes, and the low-side refrigerant is high It is assumed that heat exchange is performed with the refrigerant flowing through the refrigeration cycle 20.

The low-side expansion valve 14 expands by reducing the pressure by adjusting the flow rate of the low-side refrigerant that has passed through the low-side condenser 13. As the low-source side expansion valve 14, for example, a flow rate control means such as an electronic expansion valve, a capillary such as a capillary, a refrigerant flow rate adjustment means such as a temperature-sensitive expansion valve, or the like can be used.

The low-side evaporator 15 performs heat exchange between the low-side refrigerant decompressed by the low-side expansion valve 14 and room air such as air in a freezing room that is a cooling target. It is evaporated into a gaseous refrigerant. The object to be cooled is cooled directly or indirectly by heat exchange with the low-source refrigerant.

(High original refrigeration cycle)
The high-source refrigeration cycle 20 includes a high-side compressor 21, a high-side condenser 22, a high-side expansion valve 23, and a high-side evaporator 24. The high-source refrigeration cycle 20 forms a high-side refrigerant circuit in which the high-side refrigerant circulates by sequentially connecting these devices in a ring shape through refrigerant piping.

Further, in the high-source refrigeration cycle 20, a branch circuit 20a in which refrigerant piping branches is formed between the high-source side condenser 22 and the high-source 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 20 a is provided with a second cascade capacitor 26.

The high-end compressor 21 sucks low-temperature and low-pressure high-end refrigerant, compresses the refrigerant, and discharges it in a high-temperature and high-pressure state. As the high-end compressor 21, for example, an inverter compressor or the like whose capacity can be controlled by controlling the rotation speed by an inverter circuit or the like can be used.

The high-side condenser 22 exchanges heat between the high-side refrigerant discharged from the high-side compressor 21 and outside air such as outdoor air, and condenses and liquefies the refrigerant into a liquid refrigerant. Is. That is, the high-side condenser 22 is a heat exchanger that heats the outside air by releasing heat from the high-side 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-end condenser 22 is provided with a fan 25 for promoting heat exchange. As such a fan 25, for example, a fan capable of adjusting the air volume can be used.

The high-side expansion valve 23 is a decompression device, a throttling device, or the like, and expands by reducing the pressure by adjusting the flow rate of the high-side refrigerant that has passed through the high-side condenser 22. As the high-end side expansion valve 23, for example, a flow rate control unit such as an electronic expansion valve, a capillary tube such as a capillary, a refrigerant flow rate adjustment unit such as a temperature-sensitive expansion valve, or the like can be used.

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

The second cascade condenser 26 is a medium-high-pressure liquid high-side refrigerant condensed and liquefied by the high-side condenser 22 and a low-temperature low-pressure gaseous low-side refrigerant that is sucked into the low-side compressor 11. Exchange heat with Here, it is assumed that the temperature of the high-side refrigerant condensed and liquefied by 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 with the second cascade condenser 26, the high-side refrigerant becomes a liquid refrigerant to which a degree of supercooling is given, and flows into the high-side expansion valve 23 via the branch circuit 20a. The low-source side refrigerant becomes a gas refrigerant to which the degree of superheat is imparted, and is sucked into the low-source side compressor 11.

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

(Control device)
The control device 40 includes, for example, software executed on an arithmetic device such as a microcomputer or a CPU (Central Processing Unit), hardware such as a circuit device that realizes various functions, and the like. Control driving. For example, the control apparatus 40 is based on the operation information of the binary refrigeration apparatus 1 based on the information received from various detection means, and the operation content instruct | indicated from a user, and the low-side compressor 11 and the high-side compressor 21 , The rotational speed including ON / OFF of the fan 25, the opening degrees of the low-side expansion valve 14 and the high-side expansion valve 23, and the like are controlled.

The outside temperature sensor 41 is connected to the control device 40. The outside air temperature sensor 41 is provided for detecting 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 through each refrigeration cycle]
In the binary refrigeration apparatus 1 configured as described above, some devices of the low-source refrigeration cycle 10 such as the low-side evaporator 15 are provided in an indoor load device such as a supermarket showcase.

For example, when the pipe connection position is changed by rearranging or replacing the showcase, the refrigerant circuit will be opened locally. In such a case, the refrigerant pipes are brazed at a plurality of locations on site by a contractor. Therefore, refrigerant leakage may occur from the brazed part.

In addition, in addition to piping connections being made locally, in a normal scale supermarket, refrigeration warehouse, the length of the refrigerant piping connected to the low-source side refrigeration equipment assumed to be placed outdoors is For example, it may reach about 100 m. As a result, the number of places where pipes are connected on site increases further, so that the possibility of refrigerant leakage from the pipe connection part is further increased. On the other hand, in large supermarkets and refrigerated warehouses, the length of the refrigerant pipe may be 100 m or more. Therefore, the possibility of refrigerant leakage is further increased.

Furthermore, it is conceivable that the refrigerant pipes constructed locally will be placed in various environmental locations. For example, in a refrigerated warehouse, it may be placed in a corrosive environment due to corrosive gas generated from stored items. Corrosion of copper in a corrosive atmosphere is generally considered to be ant colony corrosion by carboxylic acid such as acetic acid, stress corrosion cracking by ammonia or the like, corrosion by acid such as sulfurous acid gas, and the like.

In addition, even when the refrigerant piping connected to the refrigeration system on the lower side is placed outdoors, sulfur-based gases such as hydrogen sulfide are used outdoors such as near hot springs and around food factories that produce processed products such as eggs. It is conceivable that corrosion of copper pipes due to sulfur-based substances occurs even in places where such a phenomenon occurs.

Normally, in such a refrigeration system, specifications are given that have anti-corrosion coating applied to the heat exchanger and the piping around the heat exchanger. It can also be selected in advance. However, when piping is constructed locally, there is no anti-corrosion specification, so it may be difficult to cope with a corrosive environment.

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

Moreover, as the high-side refrigerant circulating in the high-source refrigeration cycle 20, for example, HFO (hydrofluoroolefin) refrigerants such as HFO1234yf and HFO1234ze, refrigerants having a small influence 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-source refrigeration cycle 20, since the high-source side refrigerant circuit is not opened locally, for example, HFC (hydrofluorocarbon) refrigerants such as R32, R404A, R407C, R410A, and HFC134a, propane, isobutane, and the like A refrigerant having a high global warming potential or a mixed refrigerant containing any of these may be used.

Thus, it is preferable to use different refrigerants for the low-source side refrigerant circulating in the low-source refrigeration cycle 10 and the high-source side refrigerant circulating in the high-source refrigeration cycle 20. Further, as the high-source side refrigerant circulating in the high-source refrigeration cycle 20, it is more preferable to use a refrigerant that has higher efficiency than the low-source-side refrigerant circulating in the low-source refrigeration cycle 10.

[Operation of dual refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to Embodiment 1 will be described. Here, operation | movement of each component apparatus in a high original side refrigerant circuit and a low original side refrigerant circuit is demonstrated based on the flow of the refrigerant | coolant which flows through each refrigerant circuit.

(High refrigeration cycle operation)
First, the operation of the high-source refrigeration cycle 20 will be described. The high-side compressor 21 sucks and compresses the high-side refrigerant and discharges it in a high-temperature and high-pressure state. The discharged high-side refrigerant flows into the high-side condenser 22. The high-side condenser 22 performs heat exchange between the outside air supplied by driving the fan 25 and the high-side refrigerant, and condenses and liquefies the high-side refrigerant.

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

The high-side refrigerant condensed and liquefied by the high-side condenser 22 flows through the branch circuit 20a and also flows into the second cascade capacitor 26. The second cascade capacitor 26 exchanges heat between the high-side refrigerant condensed and liquefied and the low-side refrigerant evaporated by the low-side evaporator 15 to increase the degree of supercooling in the high-side refrigerant. Give. When the supercooling degree is given to the high-source-side refrigerant, the enthalpy in the high-source-side refrigerant circuit becomes larger than when the supercooling degree is not given. The high-side refrigerant provided with the degree of supercooling flows through the branch circuit 20 a and passes through the high-side expansion valve 23.

(Low refrigeration cycle operation)
Next, the operation of the low-source refrigeration cycle 10 will be described. The low-side compressor 11 sucks and compresses the low-side refrigerant and discharges it in a high-temperature and high-pressure state. The discharged low-source-side refrigerant flows into the auxiliary radiator 12. The auxiliary radiator 12 performs heat exchange between the outside air and the low-source side refrigerant. The low-side refrigerant that has passed through the auxiliary radiator 12 flows into the low-side condenser 13.

The low-side condenser 13 performs heat exchange between the low-side refrigerant that has flowed in and the high-side refrigerant that passes through the high-side evaporator 24 by the first cascade condenser 30. To condense. The low-side refrigerant that has been condensed and liquefied passes through the low-side expansion valve 14. The low-side expansion valve 14 depressurizes the condensed low-side refrigerant. The reduced low-side refrigerant flows into the low-side evaporator 15.

The low-side evaporator 15 performs heat exchange between the reduced-low side refrigerant and the object to be cooled, and evaporates and gasifies the low-side refrigerant. The low-source-side refrigerant that has been vaporized gas passes through the second cascade condenser 26. The second cascade condenser 26 performs heat exchange between the low-source refrigerant that has been vaporized and the high-generator refrigerant that has been condensed and liquefied, and imparts superheat to the low-source refrigerant. The low-source-side refrigerant to which the degree of superheat is imparted is sucked into the low-source-side compressor 11.

In this way, when the degree of superheat is applied to the low-side refrigerant sucked into the low-side compressor 11, the low-side refrigerant indicating the discharge temperature of the low-side refrigerant discharged from the low-side compressor 11 is shown. The discharge temperature is higher than when the superheat degree is not given. In the auxiliary radiator 12, the temperature difference between the temperature of the outside air and the low-side refrigerant discharge temperature becomes high.

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-source refrigeration cycle 20 that forms a high-side refrigerant circuit that connects and circulates the high-side refrigerant, a low-side compressor 11, an auxiliary radiator 12, a low-side condenser 13, and a low-side expansion valve 14 , And a low-side refrigeration cycle 10 forming a low-side refrigerant circuit that circulates the low-side refrigerant and a high-side evaporator 24 and a low-side condenser 13. And a first cascade condenser 30 that exchanges heat between the high-end refrigerant flowing through the high-end refrigerant circuit and the low-end refrigerant flowing through the low-end refrigerant circuit. In addition, the binary refrigeration apparatus 1 is provided in the branch circuit 20a that branches from the downstream of the high-side condenser 22 in the high-source refrigeration cycle 20 and returns to the upstream of the high-side expansion valve 23, and the branch circuit 20a. A second cascade condenser 26 that exchanges heat between the high-end refrigerant flowing through the circuit 20a and the low-end refrigerant flowing out of the low-end evaporator 15, and each device provided in the binary refrigeration apparatus 1 And a control device 40 for controlling the operation.

In this way, in the second cascade capacitor 26, the high original refrigerant flowing through the branch circuit 20a and the low original refrigerant flowing out of the low original evaporator 15 perform heat exchange, whereby the high original refrigerant Since the temperature is higher than the temperature of the low-source side refrigerant, the degree of supercooling is given to the high-source side refrigerant. At the same time, the degree of superheat is imparted to the low-source refrigerant.

And, since the enthalpy in the high-side refrigerant circuit is increased by giving the degree of supercooling to the high-side refrigerant, the refrigeration capacity of the high-side refrigerant circuit, that is, the high-source refrigeration cycle 20 is improved. Can do. Further, the capacity of the high-end compressor 21 can be reduced.

Furthermore, since the degree of superheat of the low-side refrigerant sucked into the low-side compressor 11 is increased by giving the superheat degree to the low-side refrigerant, the low-side side in the low-side compressor 11 The refrigerant discharge temperature can be increased. In this way, the temperature of the low-source side refrigerant flowing into the auxiliary radiator 12 can be made higher than before. Therefore, the temperature difference with the outside air which performs heat exchange in the auxiliary radiator 12 can be increased, the amount of heat exchange in the auxiliary radiator 12 can be improved, and the auxiliary radiator 12 can be effectively used.

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 described above in that a flow rate adjusting valve is provided in the branch circuit 20a of the high-side refrigerant circuit.

[Configuration of dual refrigeration system]
FIG. 2 is a block diagram illustrating an example of the configuration of the binary refrigeration apparatus 1 according to the second embodiment. In the following description, the same reference numerals are given to the portions common to the above-described first embodiment, and the detailed description is omitted. As shown in FIG. 2, the binary refrigeration apparatus 1 includes a low-source refrigeration cycle 10, a high-source refrigeration cycle 20, a first cascade capacitor 30, and a control device 40, as in the first embodiment. A branch circuit 20 a is provided in the high-side refrigerant circuit of the refrigeration cycle 20.

In the second embodiment, the branch circuit 20a is provided with a flow rate adjusting valve 42. A discharge temperature sensor 43 is provided on the discharge side of the low-source compressor 11.

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

When the flow rate adjustment valve 42 is opened, the flow rate of the high-side refrigerant that is heat-exchanged by the second cascade condenser 26 increases, and the degree of superheat of the low-side refrigerant that is sucked into the low-side compressor 11 increases. For this reason, the temperature of the low-side refrigerant discharged from the low-side compressor 11 becomes high.

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

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

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

[Operation of dual refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to the second embodiment will be described. In the following description, detailed description of operations similar to those of the first embodiment described above is omitted. Further, the low-source refrigeration cycle 10 is the same as that in the first embodiment, and thus the description thereof is omitted.

(High refrigeration cycle operation)
In the second embodiment, the operation from when the high-side refrigerant is sucked into the high-side compressor 21 until it is condensed and liquefied by the high-side condenser 22 is the same as that of the above-described 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 rate adjustment valve 42 is set to the “open” state. In this case, the high-side 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 high-side refrigerant that has flowed into the branch circuit 20a flows into the second cascade condenser 26 and exchanges heat with the low-side refrigerant that has been vaporized and gasified by the low-side evaporator 15. Thereby, a supercooling degree is provided to the high-source side refrigerant. The high-side refrigerant provided with the degree of supercooling flows through the branch circuit 20 a and passes through the high-side 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 rate adjustment valve 42 is in a “closed” state, and in this case, the low-side side refrigerant 22 is condensed and liquefied by the high-side condenser 22. The high-side refrigerant does not flow into the branch circuit 20a and passes through the high-side expansion valve 23. The high-side refrigerant that has passed through the high-side expansion valve 23 is decompressed and flows into the high-side evaporator 24. The high-side refrigerant flowing into the high-side evaporator 24 is heat-exchanged with the low-side refrigerant passing through the low-side condenser 13 by the first cascade condenser 30, and is evaporated and gasified. Is done. Then, the high-side refrigerant that has been vaporized is sucked into the high-side compressor 21.

Here, the heat exchange amount in the heat exchanger will be described. The heat exchange amount Q [W] indicating the capability of the heat exchanger can be generally expressed by the formula (1). In Equation (1), “K” indicates the heat passage rate [W / m ² · K] of the heat exchanger, and is determined by the specifications of the heat exchanger and the air volume combined in the case of the air heat exchanger. 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 the 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, it is possible to increase the average temperature difference [Delta] T _m, it is possible to increase the heat exchange amount Q.

Therefore, in the second embodiment, the low-end side refrigerant discharge temperature in the low-end side compressor 11 can be increased by controlling the opening degree of the flow rate adjusting valve 42, and thereby the auxiliary radiator 12. As a result, the temperature of the low-side refrigerant flowing into the refrigerant 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-source refrigeration cycle 10 and the high-source refrigeration cycle 20 will be described. For example, a case is considered in which, based on control by the control device 40, the opening degree of the low-side expansion valve 14 is increased so that the low-side refrigerant flowing out of the low-side evaporator 15 enters a gas-liquid two-phase state. . In this case, since all the low-side refrigerants in the low-side evaporator 15 are in the gas-liquid two-phase state, the low-side refrigerant in the gas-liquid two-phase state and the cooling target such as air in the refrigerator Will exchange heat. Thereby, average temperature difference (DELTA) _Tm of the low original side refrigerant | coolant shown to Formula (1) mentioned above and cooling object can be made larger than a normal state. Therefore, since the heat exchange amount Q in the low element side evaporator 15 can be increased, the cooling capacity of the low element refrigeration cycle 10 can be improved.

Also, the amount of heat exchange in the second cascade condenser 26 that performs heat exchange between the low-side refrigerant flowing out of the low-side evaporator 15 and the high-side refrigerant flowing through the branch circuit 20a also increases. Therefore, the degree of supercooling imparted to the high-source-side refrigerant can be increased, and the enthalpy in the high-source-side refrigerant circuit is increased, so that the refrigeration capacity of the high-source 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 by the outside air temperature sensor 41 and the discharge temperature sensor 43. Based on the detection result, the opening degree of the flow rate adjustment valve 42 is controlled.

As described above, in the second embodiment, the opening degree of the flow rate adjustment valve 42 is controlled based on the low-source refrigerant discharge temperature detected by the discharge temperature sensor 43 and the outside air temperature detected by the outside air temperature sensor 41. To do. Therefore, the temperature difference between the low-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. As a result, even when the low-side refrigerant discharge temperature in the low-side compressor 11 is difficult to rise and the evaporation temperature of the low-side evaporator 15 is high, the cooling capacity 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 problems such as failure of the compressor. In the second embodiment, the temperature of the low-side refrigerant sucked into the low-side compressor 11 is adjusted by controlling the opening degree of the flow rate adjustment valve 42, and the low-side side in the low-side compressor 11 is adjusted. The refrigerant discharge temperature can be adjusted. For this reason, it is possible to prevent a malfunction of the low-side compressor 11 due to an increase in the low-side refrigerant discharge temperature, and to extend the life of the low-side compressor 11.

Embodiment 3 FIG.
Next, the binary refrigeration apparatus 1 according to the third embodiment will be described. The third embodiment is 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 described above.

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

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

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

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 capacitor 26 provided in the low-source side injection circuit 10a flows through the high-side refrigerant flowing through the high-side branch circuit 20a and the low-side injection circuit 10a and is throttled by the injection expansion valve 51. Heat exchange is performed with the low-side refrigerant in the low-temperature low-pressure gas-liquid two-phase state.

[Operation of dual refrigeration system]
Next, the operation of the binary refrigeration apparatus 1 according to the third embodiment will be described. In the following description, detailed description of the same operations as those in the first embodiment and the second embodiment described above will be omitted. Further, the high-source refrigeration cycle 20 is the same as that of the second embodiment, and thus the description thereof is omitted.

(Low refrigeration cycle operation)
In the third embodiment, the operation from when the low-side refrigerant is sucked into the low-side compressor 11 until it is condensed and liquefied by the low-side condenser 13 is described in the first embodiment and the above-described embodiment. Since it is the same as 2, 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 low-side refrigerant flowing into the low-side injection circuit 10 a passes through the injection expansion valve 51. The injection expansion valve 51 squeezes the condensed low liquefied refrigerant to form a low-temperature low-pressure gas-liquid two-phase low-source refrigerant.

At this time, the low-side refrigerant that has passed through the injection expansion valve 51 and has entered a low-temperature low-pressure gas-liquid two-phase state passes through the low-side evaporator 15 and is sucked into the low-side compressor 11. The pressure is the same as that 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-side compressor 11.

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

Here, the low-side refrigerant passing through the second cascade condenser 26 is applied by the low-side evaporator 15 as compared with the low-temperature and low-pressure gasified low-side refrigerant passing through the low-side evaporator 15. The temperature is lowered by the degree of superheat. This is obtained by adding the degree of superheat given by the low-side evaporator 15 to the saturation temperature in which the temperature of the low-side refrigerant that has passed through the low-side evaporator 15 is converted from the low pressure on the low side. This is because the temperature of the low-side refrigerant that has passed through the injection expansion valve 51 is a saturation temperature converted from the low-pressure on the low-side side. Therefore, the temperature difference between the low-side refrigerant and the high-side refrigerant that is heat-exchanged in the second cascade condenser 26 is lower than the temperature difference in the second embodiment when it passes through the low-side evaporator 15. It increases by the degree of superheat imparted to the former refrigerant.

Therefore, a higher supercooling degree than that of the second embodiment is given to the high-side refrigerant that is a high-temperature and high-pressure liquid refrigerant that performs heat exchange with the second cascade condenser 26. Thereby, in this Embodiment 3, the enthalpy of the high yuan side can be enlarged and the refrigerating capacity of the high refrigeration cycle 20 can be improved. Thereby, a compressor with a small capacity can be used as the high-end compressor 21.

As described above, the binary refrigeration apparatus 1 according to Embodiment 3 includes the low-side evaporator 13 and the low-side compressor 11 between the low-side condenser 13 and the low-side expansion valve 14. And a low expansion side injection circuit 10a connected to the low expansion side injection circuit 10a. The control device 40 is based on the detection result by the discharge temperature sensor 43, and the injection expansion valve The opening of 51 is controlled.

As a result, the temperature difference between the low-side refrigerant and the high-side refrigerant that performs heat exchange with the second cascade capacitor 26 can be made larger than those in the first and second embodiments, so that the high-side enthalpy is reduced. The refrigeration capacity of the high-source refrigeration cycle 20 can be further improved.

Embodiment 4 FIG.
Next, the binary refrigeration apparatus 1 according to the fourth embodiment will be described. The fourth embodiment is different from the third embodiment described above in that an intake temperature sensor for detecting the temperature of the low-side refrigerant sucked on the suction side of the low-side compressor 11 is provided.

[Configuration of dual refrigeration system]
FIG. 4 is a block diagram illustrating an example of the configuration of the binary refrigeration apparatus 1 according to the fourth embodiment. In the following description, the same reference numerals are given to portions common to the above-described first to third embodiments, and detailed description thereof is omitted. As shown in FIG. 4, the binary refrigeration apparatus 1 includes a low-source refrigeration cycle 10 provided with a low-source injection circuit 10a and a high-source refrigeration cycle 20 provided with a branch circuit 20a, as in the third embodiment. The first cascade capacitor 30 and the control device 40 are included.

In the fourth embodiment, a suction temperature sensor 44 is provided on the suction side of the low-source compressor 11. The suction temperature sensor 44 is provided to detect a low-source-side refrigerant suction temperature indicating the suction temperature of the low-source-side refrigerant sucked into the low-source side compressor 11. The suction temperature sensor 44 supplies information indicating the detected low-source side refrigerant suction temperature to the control device 40.

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

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

As described above, the binary refrigeration apparatus 1 according to the fourth embodiment 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 includes 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 operation range of the low-side compressor 11 can be secured, and problems such as a failure of the low-side compressor 11 can be prevented.

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

1 Low refrigeration cycle, 10 Low refrigeration cycle, 10a Low low side injection circuit, 11 Low low side compressor, 12 Auxiliary radiator, 13 Low low side condenser, 14 Low low side expansion valve, 15 Low low side evaporation , 20 high refrigeration cycle, 20a branch circuit, 21 high high side compressor, 22 high high side condenser, 23 high high side expansion valve, 24 high high side evaporator, 25 fan, 26 second cascade condenser, 30 1st cascade capacitor, 40 control device, 41 outside air temperature sensor, 42 flow rate adjustment valve, 43 discharge temperature sensor, 44 suction temperature sensor, 51 injection expansion valve.

Claims

A high-source refrigeration cycle that forms a high-side refrigerant circuit that connects the high-side compressor, the high-side condenser, the high-side expansion valve, and the high-side evaporator through piping and circulates the high-side refrigerant. ,
A low-side compressor, auxiliary radiator, low-side condenser, low-side expansion valve, and low-side evaporator are connected by piping to form a low-side refrigerant circuit that circulates the low-side refrigerant. The original refrigeration cycle,
Heat is generated between the high-side refrigerant flowing through the high-side refrigerant circuit and the low-side refrigerant flowing through the low-side refrigerant circuit, having the high-side evaporator and the low-side condenser. A two-stage refrigeration apparatus comprising a first cascade condenser for exchange,
A branch circuit that branches from the downstream of the high-side condenser in the high-source refrigeration cycle and returns to the upstream of the high-side expansion valve;
A second cascade capacitor provided in the branch circuit for exchanging heat between the high-side refrigerant flowing through the branch circuit and the low-side refrigerant flowing out of the low-side evaporator;
A binary refrigeration apparatus comprising: a control device that controls operation of each device provided in the binary refrigeration apparatus.
An outside air temperature sensor for detecting the outside air temperature;
A discharge temperature sensor for detecting a discharge temperature of the low-side refrigerant discharged from the low-side compressor;
A flow rate adjustment valve that adjusts the flow rate of the high-source side refrigerant flowing into the branch circuit;
The controller is
2. The dual refrigeration apparatus according to claim 1, wherein the opening degree of the flow rate adjustment valve is controlled based on a detection result by the outside air temperature sensor and a detection result by the discharge temperature sensor.
The controller is
The binary refrigeration apparatus according to claim 1 or 2, wherein an opening degree of the low-side expansion valve is controlled so that the low-side refrigerant flowing out of the low-side evaporator is in a gas-liquid two-phase state.
An 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;
An injection expansion valve provided in the injection circuit,
The controller is
The binary refrigeration apparatus according to claim 2, wherein the opening degree of the injection expansion valve is controlled based on a detection result by the discharge temperature sensor.
A suction temperature sensor for detecting a suction temperature of the low-side refrigerant sucked into the low-side compressor;
The controller is
The binary refrigeration apparatus according to claim 4, wherein the 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.
In the high original side refrigerant and the low original side refrigerant,
The binary refrigeration apparatus according to any one of claims 1 to 5, wherein different refrigerants are used.
In the low original side refrigerant,
The binary refrigeration apparatus according to any one of claims 1 to 6, wherein a refrigerant having higher efficiency than the high-source side refrigerant is used.
At least one of the high-side refrigerant and the low-side refrigerant is
The binary refrigeration apparatus according to any one of claims 1 to 7, wherein a carbon dioxide refrigerant or a mixed refrigerant containing carbon dioxide is used.
At least one of the high-side refrigerant and the low-side refrigerant is
The refrigerant according to any one of claims 1 to 8, wherein a refrigerant of any one of R32, R410A, R134a, R404A, R407C, HFC1234yf, HFO1234ze, ammonia, propane, and isobutane, or a mixed refrigerant containing any of these is used. Dual refrigeration equipment.