JP2854079B2 - Multi-source refrigeration equipment - Google Patents

Description

The present invention relates to a multi-source refrigerator for exchanging heat between an evaporator of a high-temperature refrigeration cycle and a condenser of a low-temperature refrigeration cycle.

(B) Conventional technology As an example of a binary refrigeration system, Japanese Utility Model Publication No. 56-53236
There is an official gazette. In this publication, heat exchange between an evaporator of a high-temperature side refrigeration cycle and a condenser of a low-temperature side refrigeration cycle is performed by a cascade condenser.

Here, a refrigerant having a relatively low boiling point (for example, R-22) is generally sealed in the high-temperature side refrigeration cycle, and a refrigerant having a relatively high boiling point (for example, R-13) is sealed in the low-temperature side refrigeration cycle. It is.

(C) Problems to be Solved by the Invention Since the boiling point of the refrigerant sealed in the low-temperature side refrigeration cycle is high, this refrigerant gasifies during operation stop, and the refrigerant pressure in the low-temperature side refrigeration cycle becomes low. May be higher. When the operation is restarted in this state, the high-low pressure difference of the refrigerant in the low-temperature side refrigeration cycle cannot be quickly set to the set value, and there is a possibility that stable refrigeration capacity cannot be quickly exhibited.

An object of the present invention is to promptly exhibit a stable refrigeration capacity.

(D) Means for Solving the Problems In order to achieve this object, the present invention provides a compression adjusting valve in a suction pipe of a compressor of a low-temperature side refrigeration cycle of a multi-stage refrigeration apparatus.

(E) Action During operation stoppage, the boiling point sealed in the low-temperature side refrigeration cycle evaporates and the refrigerant pressure in this low-temperature side refrigeration cycle increases, and when the compressor is operated in the high state, the pressure regulating valve As a result, the pressure of the refrigerant sucked into the compressor is set to a predetermined value or less, whereby the pressure difference of the refrigerant in the low-temperature side refrigeration cycle is quickly set to the predetermined value.

(F) Embodiment In FIGS. 1 and 2, reference numeral 1 denotes a binary refrigeration system, which is composed of a high-temperature unit 2, a low-temperature unit 3, and a cooler unit 4. These units 2, 3, and 4 are connected by a refrigerant pipe (described later).

Reference numeral 5 denotes a high-temperature side refrigeration cycle, which functions as a compressor 6, a muffler 7, a condenser 8, a first liquid receiver 9, a dryer 10, a first control valve 11, a first expansion (decompressor) 12, and a subcooler. The subcooler 13, the evaporator 14, and the accumulator 15 are sequentially connected by a refrigerant pipe. The refrigerant sealed in the high-temperature side refrigeration cycle 5 is R-22. Reference numeral 16 denotes a temperature sensor attached to the low-pressure side pipe. The opening of the first expansion valve 12 is controlled based on the temperature detected by the sensor 16. The first control valve 11 is closed during the pump-down operation performed after the cooling operation of the refrigeration cycle 5 is stopped, and the refrigerant in the evaporator 14 is supplied to the high-pressure side pipe of the refrigeration cycle 5 (such as the condenser 8). Is to be collected.

Reference numeral 17 denotes a low-temperature refrigeration cycle, which includes a compressor 18, a muffler 19, an oil separator 20, a condenser 21, a second liquid receiver 34, a subcooler 13, a dryer 22, a second expansion valve (decompressor) 23, and an evaporator.
24, a suction pressure adjusting valve 25, and an accumulator 26 are sequentially connected by a refrigerant pipe. Reference numeral 27 denotes an oil return pipe for returning the oil stored in the oil separator 20 to the compressor 18. The condenser 21 of the low-temperature refrigeration cycle 17 and the evaporator 14 of the high-temperature refrigeration cycle 5 are connected by a cascade condenser.
The condenser 21 of the low-temperature side refrigeration cycle 17 and the evaporator 14 of the high-temperature side refrigeration cycle 5 exchange heat. The refrigerant sealed in the low-temperature side refrigeration cycle 17 is R-13. Reference numeral 29 denotes a temperature sensor attached to the low-pressure side pipe. The opening of the second expansion valve 23 is controlled based on the temperature detected by the sensor 29.
Reference numeral 30 denotes an expansion tank, and 31 denotes one bypass pipe, one end of which is connected to the inlet side of the condenser 21, that is, the high pressure side pipeline 32, and the other end of which is connected to the upper part of the expansion tank 30. Reference numeral 33 denotes a second control valve provided in the one bypass pipe 31, which is a low-temperature side refrigeration cycle 17.
The compressor 18 is closed when the compressor 18 is in operation, and is opened when the operation is stopped. The second control valve 33 is an electromagnetic valve generally called an “energized open type”. Reference numeral 35 denotes the other bypass pipe, one end of which is connected to the lower portion of the expansion tank 30 and the other end of which is connected to the inlet side of the suction pressure adjusting valve 25, that is, the low pressure side pipe. Since the second control valve 33 is opened when the operation of the compressor 18 is stopped, the liquid refrigerant in the condenser 21 of the low-temperature side refrigeration cycle 17 is supplied to the high-pressure side line 32 and one of the bypass pipes when the operation is stopped. 31
Through the expansion tank 30. The aforementioned suction pressure regulating valve 25 has a refrigerant pressure in its inlet side pipeline 36 of, for example, 5 kg / cm.
If it is ² or more, the opening degree of the valve 25 is reduced, the refrigerant pressure is reduced to about 5 kg / cm ² , and the refrigerant is returned to the compressor 18. This prevents the pressure of the refrigerant sucked into the compressor 18 from becoming abnormally high, thereby preventing an abnormal increase in the (high pressure) pressure of the refrigerant discharged from the compressor 18. Reference numeral 39 denotes a delay device (delay means) which is connected to the compressor 6 of the high-temperature side refrigeration cycle 5 and the compressor 18 of the low-temperature side refrigeration cycle 17, and 60 seconds after the start of operation of the compressor 6 of the high-temperature side refrigeration cycle 5. A signal is output to the compressor 18 so that the operation of the compressor 18 of the low-temperature side refrigeration cycle 17 starts.

The binary refrigeration system having such a configuration is separated into a high-temperature unit 2, a low-temperature unit 3, and a cooler unit 4, and the high-temperature unit 2 includes a compressor 6 and a condenser 8 of a high-temperature refrigeration cycle 5. The low-temperature unit 3 includes a cascade condenser 28 and a compressor for the low-temperature refrigeration cycle 17.
The cooler unit 4 incorporates an evaporator 24 of the low-temperature side refrigeration cycle 17. By doing so, if there is no space for both the low-temperature unit 3 and the high-temperature unit 2 near the freezer (not shown) having the cooler unit 4, the low-temperature unit 3
Only the high-temperature side unit 2 can be placed near this freezer compartment, and at another place. Here, the low-temperature side unit 3
Piping between low-temperature units connecting the air conditioner and the cooler unit 4
The temperature of 37 (the temperature of the refrigerant flowing in the low-temperature side unit pipe 37) is the temperature of the high-temperature side unit pipe 38 connecting the high-temperature side unit 2 and the low-temperature side unit 3 (flowing in the inter-unit pipe 38). Lower than the temperature of the refrigerant), but the length of the low-temperature side unit piping 37 can be kept short (because the distance between the low-temperature unit 3 and the cooler unit 4 is short). Heat loss can be reduced. If there is a space near the freezer compartment, the high-temperature unit 2 and the low-temperature unit 3 may be arranged side by side as shown in FIG. Further, the low-temperature unit 3 and the cooler unit 4 may be integrally combined, and only the high-temperature unit 2 may be separated.

Next, an operation state of the binary refrigeration apparatus 1 will be described. At the start of operation, first, the compressor 6 of the high-temperature side refrigeration cycle 5 is operated, the first control valve 11 is opened, and the refrigerant flows as shown by the solid line arrow in FIG. Here, before the start of the operation, that is, before the end of the previous operation, the first control valve 11 is closed to perform the pump-down operation, and the refrigerant in the evaporator 14 is collected in the high-pressure side pipe such as the condenser 8. . Therefore, since the operation is started in a state where there is no refrigerant in the evaporator 14, the evaporator 14 is quickly cooled by the refrigerant flowing after the start. Then, after a lapse of 60 seconds (predetermined time) from the start of operation of the compressor 6 of the high temperature side refrigeration cycle 5 by the delay device 39, the operation of the compressor 18 of the low temperature side refrigeration cycle 17 is started. The reason why the operation of the compressor 18 of the low-temperature refrigeration cycle 17 is delayed from the start of operation of the compressor 6 of the high-temperature refrigeration cycle 5 by the delay device 39 is that the high-temperature refrigeration cycle 5
This is because it is desired to lower the temperature of the evaporator 14 to some extent before flowing the refrigerant into the condenser 21 of the low-temperature refrigeration cycle 17. This shortens the rise time of the low-temperature side refrigeration cycle 17. Further, the temperature of the evaporator 14 of the high-temperature side refrigeration cycle 5 can be reduced to a certain degree by the predetermined time, thereby keeping the heat exchange capacity of the cascade condenser 28 constant. This predetermined time is variable depending on the size of the binary refrigeration system. A temperature sensor is attached to the outlet pipe of the evaporator 14 of the high-temperature side refrigeration cycle 5 instead of the delay device 39 described above, and when the temperature detected by this sensor falls below a certain value, the compressor 18 of the low-temperature side refrigeration cycle 17 is operated. I thought about making it happen. However, as described above, due to the pump-down operation, immediately after the start of the operation, the refrigerant flows from the evaporator 14 without any refrigerant into the evaporator 14 at once, so that the temperature of the outlet pipe of the evaporator 14 rapidly decreases (for several seconds). Changes from 30 ° C. to 0 ° C.).
There is a possibility that the temperature sensor cannot keep up with such a rapid change, and the instruction to start the operation of the compressor 18 of the low-temperature side refrigeration cycle 17 cannot be given accurately.

In this way, the two compressors 6 and 18 start to operate together to cool the freezing room in which the evaporator 24 of the low-temperature side refrigeration cycle 17 is stored. Here, in the low-temperature side refrigeration cycle 17, most of the refrigerant discharged from the compressor 18 is condensed and liquefied in the condenser 21 in the cascade condenser 28, but part of the refrigerant flows out of the condenser 21 without being liquefied. May be done. The gas refrigerant in such a case is supplied to the second liquid receiver.
Stored in the upper part of 34. Then, the liquid refrigerant flowing out of the liquid receiver 34 flows into the subcooler 13. The subcooler 13 cools the liquid refrigerant to a supercooled state,
The expansion valve 23 receives a pressure reducing action. As described above, the liquid refrigerant that has flowed out of the condenser 21 is temporarily stored in the second liquid receiver 34, is supercooled by the subcooler 13, and flows into the second expansion valve 23. There is no fear that the flush gas flows into the valve 23 and makes the operation (valve opening) of the second expansion valve 23 unstable. Therefore, the operation state of the second expansion valve 23 can be improved to obtain a stable refrigeration capacity. In addition, since the boiling point of the refrigerant (R-13) in the low-temperature refrigeration cycle 17 is higher than the boiling point of the refrigerant (R-22) in the high-temperature refrigeration cycle, the refrigerant is easily gasified. By doing so, this gasification can be prevented beforehand, and the expansion tank 30 can be downsized.

Since a suction pressure adjusting valve 25 is provided in the suction pipe of the compressor 18 of the low temperature side refrigeration cycle 17, if the set value of the adjusting valve 25 is set to, for example, 5 kg / cm ² , the evaporator 24
Even if the nearby refrigerant pressure is 5 kg / cm ² or more, the compressor 1
The pressure of the refrigerant sucked into 8 is kept at 5 kg / cm ² . As described above, the pressure of the refrigerant sucked into the compressor 18 is prevented from being equal to or higher than the predetermined value by the adjusting valve 25, so that the high / low pressure difference of the low temperature side refrigeration cycle 17 can be quickly and constantly maintained. If such a suction pressure adjusting valve 25 is not provided, it takes much time to keep the high / low pressure difference constant. And there was a possibility that stable refrigerant capacity could not be exhibited quickly.

Next, when the cooling operation is stopped, the second control valve 33 is opened (closed during the cooling operation), and the liquid refrigerant in the condenser 21 is led to the expansion tank 30 via the bypass pipe 31. Thus, when the cooling operation is stopped, the low-temperature side refrigeration cycle
The liquid refrigerant in the condenser 21 of 17 is made to flow into the expansion tank 30 and the low-pressure pipe of the refrigeration cycle. That is, the liquid refrigerant is poured into the expansion tank 30 and the low-pressure side pipe which are at a low temperature when the operation is stopped, so that the vaporization of the liquid refrigerant is suppressed as much as possible. As a result, the pressure increase of the refrigerant at the time of stopping the operation is suppressed to be small, and the expansion tank 30 can be downsized.

After the cooling operation is completed, the compressor of the low-temperature refrigeration cycle 17
At the same time, the operation of the compressor 6 of the high-temperature side refrigeration cycle 5 is continued, the first control valve 11 is closed, and the pump-down operation is performed. By this pump-down operation, the refrigerant in the subcooler 13 and the evaporator 14 is recovered to the high-pressure-side pipe such as the condenser 8, and the evaporator 14 is in a state where there is no refrigerant. Therefore, when the cooling operation is restarted (the operation of the compressor 6 of the high-temperature side refrigeration cycle 5 is regenerated), the evaporator 14 is quickly cooled by the refrigerant flowing into the evaporator 14 simultaneously with the restart. As a result, the operation of the compressor 18 of the low-temperature side refrigeration cycle 17 is restarted, and the refrigerant discharged from the compressor 18 is quickly cooled by the condenser 21.

(G) Effect of the Invention As described above, in the present invention, the suction pipe of the compressor of the low-temperature refrigeration cycle of the multi-stage refrigeration system is provided with a pressure regulating valve. When operated, the pressure of the refrigerant sucked into the compressor by the pressure regulating valve is set to a predetermined value or less. As a result, the pressure difference of the refrigerant in the low-temperature side refrigeration cycle is quickly set to a predetermined value, and a stable refrigeration capacity can be quickly exhibited.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a refrigerant circuit diagram of a binary refrigeration apparatus, and FIG. 2 is a perspective view showing a state in which a high-temperature side unit and a low-temperature side unit of this apparatus are arranged. 5 ... high temperature side refrigeration cycle, 14 ... evaporator, 17 ... low temperature side refrigeration cycle, 18 ... compressor, 21 ... condenser, 25 ...
Pressure regulating valve.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25B 1/00 304 F25B 7/00

Claims (1)

(57) [Claims] In a multi-stage refrigeration system for exchanging heat between an evaporator with a high-temperature refrigeration cycle and a condenser with a low-temperature refrigeration cycle, a suction pipe of a compressor of the low-temperature refrigeration cycle has a pressure higher than a set value. A multi-stage refrigeration apparatus comprising a pressure adjusting valve for reducing a refrigerant having a pressure to a substantially set value and returning the refrigerant to a compressor.