JPH0827084B2 - Method and device for returning oil from liquid receiver in low temperature side cycle of dual refrigeration system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for returning oil from a low temperature side refrigerant receiver in a low temperature side cycle of a dual refrigeration system. Especially, the refrigerating machine oil staying in the low-source side refrigerant receiver is extracted together with the refrigerant liquid, heat-exchanged with the discharge gas from the low-source side compressor, the refrigerant liquid is vaporized and separated, and then the refrigerating machine oil is converted into the low-source side low pressure oil. The present invention relates to a method and apparatus for returning oil to a crankcase of a low-pressure side compressor via a separator.

[0002]

PRIOR ART Freon (R12.R22.R502 etc.)
In a normal refrigerating apparatus in which the refrigerant is used as a refrigerant, the refrigerating cycle of the refrigerant forms one cycle of refrigerating machine oil, and the refrigerating machine oil and the refrigerating machine oil go around the inside of the apparatus and return to the compressor. That is, part of the refrigerating machine oil that lubricates the inside of the compressor is
Although it is discharged from the discharge port together with the refrigerant gas and separated by the oil separator and returns to the compressor, the oil that cannot be completely separated goes around the device (including the evaporator) together with the refrigerant and returns to the compressor. .

However, in the ultra low temperature refrigeration system, R23 has come to be used in the low temperature side cycle of the dual refrigeration system, and the temperature of the low side compressed gas rises, so that the low side low pressure oil separator Oil separation is poor. Then, two layers are separated and accumulated in the upper portion of the refrigerant liquid in the low-source-side refrigerant receiver after passing through the low-source-side refrigerant condenser, and cannot return to the low-source side compressor. For this reason, the low-pressure side compressor has poor lubrication, and refrigerating machine oil must be newly supplied.

Further, the oil staying above the refrigerant surface in the low-side refrigerant receiver has a high sticking degree and is difficult to extract, and the oil flowing into the low-side evaporator is defrosted in this evaporator. There is also a method in which the inside and outside of the evaporator are heated in combination with the above, and returned to the low-side compressor crankcase together with the refrigerant gas. However, in this method, the oil staying in the low-end side refrigerant receiver is temporarily taken out from the upper part of the liquid surface of the refrigerant of this receiver into an oil reservoir and heated by a high-pressure refrigerant gas, an electric heater, a hot water heater, etc. Then, the liquid refrigerant is evaporated. The present situation is that the gasified refrigerant is sucked by the low-pressure side compressor, and then the oil is taken out through a three-step or four-step process.

[0005]

Therefore, extra energy and time are spent for the treatment of oil, and the low-pressure side compressor is temporarily stopped during the treatment, so that the refrigeration temperature rises during that period. Therefore, there is a drawback that energy and time are required to recover the refrigerating temperature, and a vicious cycle in which the quality of the refrigerating product is deteriorated is repeated.

Further, in the low temperature side cycle of the dual refrigeration system, the oil discharged together with the refrigerant gas from the low source side compressor discharge port into the low source side refrigerant receiver is supplied to the low source side refrigerant condenser and the liquid receiver. There is a problem that the compressor is poorly lubricated because it stays in the container and does not return to the low-pressure side compressor. Therefore, refrigerating machine oil must be replenished, refrigerating machine oil replenishment is limited, continuous operation cannot be performed for a long time, and it is necessary to temporarily stop the low-side compressor and take oil treatment. However, during that time, the refrigeration temperature increased, and there were the same drawbacks as described above.

Further, if a large amount of oil stays in the low-level side refrigerant receiver, there is a drawback that the flow of the low-level side refrigerant is hindered.

The present invention eliminates these drawbacks and problems,
An object of the present invention is to provide a method and an apparatus for returning oil from a receiver in a low-temperature cycle of a dual refrigeration system that returns refrigerating machine oil accumulated in a low-source refrigerant condenser and a receiver to a low-source compressor. To do.

[0009]

In order to solve this problem, in the present invention, as a method for returning oil from a low-source refrigerant receiver, a low-source side in a low-temperature cycle of a dual refrigeration system is used. Refrigerating machine oil that has separated into two layers from the refrigerant liquid in the refrigerant receiver and stays is extracted together with the refrigerant liquid existing in the surroundings. Further, this refrigerating machine oil is decompressed together with the refrigerant liquid, and heat is exchanged with the discharge gas of the low-pressure side compressor.

Then, the mixed refrigerant liquid is vaporized and separated, and the refrigerant gas is returned to the gas suction side of the low-source side low-pressure compressor, and the low-source side low-pressure oil separator and the low-source side compressor are connected. Adjust the evaporation pressure to keep the evaporation pressure and temperature in the liquid / gas heat exchanger and in the low pressure side low pressure oil separator constant. Further, the temperature of this refrigerating machine oil is maintained above its pour point and returned to the crankcase of the low-side compressor.

As an oil returning device from the low-source refrigerant receiver 7, a low-source high-pressure oil separator on the discharge side of the low-source compressor and a low-source refrigerant are used in the low-temperature cycle of the dual refrigeration system. A liquid / gas heat exchanger is interposed between the condensers. Then, connect a plurality of oil drain pipes with stop valves from the low side refrigerant receiver to the heat transfer pipe inlet of the liquid / gas heat exchanger with an automatic expansion valve for low side oil recovery interposed. , The tube from the heat transfer tube outlet is connected to a separate low pressure side low pressure oil separator.

The lower float valve in this low pressure side low pressure oil separator is connected to the pipe to the crankcase of the low pressure side compressor. Further, the gas outlet of the low-pressure side low-pressure oil separator and the compressor low-pressure side suction pipe were connected with an evaporation pressure adjusting valve for the liquid / gas heat exchanger interposed.

[0013]

Operation: Between the low side compressor 28 and the low side refrigerant condenser 6 in the low temperature side cycle of the dual refrigeration system (the low side low pressure oil separator 1
If there are two, a liquid / gas heat exchanger 10 is provided between these oil separator 12 and condenser 6. Then, the oil accumulated in the low-source side refrigerant receiver 7 in the heat exchanger 10 is adjusted in flow rate through the low-source side oil recovery automatic expansion valve 11 together with the refrigerant liquid existing around it. While sending. Then, the refrigerant liquid is evaporated in the heat exchanger 10 to separate the oil, and the oil is allowed to flow into the low-pressure side low-pressure oil separator 12.

At this time, since the suction pressure of the low-pressure side compressor 28 is low, the temperature of the oil decreases, and the oil does not flow below the pour point, so that the low-pressure side low pressure oil separator 12 and the low-pressure side compressor. Two
A vaporization pressure control valve 14 for a liquid / gas heat exchanger is installed between 8 and 8. Then, by keeping the evaporation pressure (temperature) of the refrigerant in the liquid / gas heat exchanger 10 and the low-pressure side low-pressure oil separator 12 constant, the refrigerant is evaporated and separated while maintaining the fluidity of the oil. is there.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for returning oil from a liquid receiver in a low temperature side cycle of a dual refrigeration system according to the present invention and an embodiment of the device will be described in detail below with reference to the accompanying drawings.
FIG. 1 shows a piping system diagram of an oil return device from a liquid receiver of the present invention.

In the high temperature side cycle of the dual refrigeration system, from the discharge port of the high pressure side compressor 1 to the high pressure side high pressure gas pipe 27 through the high pressure side oil separator 4 and the high pressure side refrigerant condensation provided with the blower 3. The condenser 2 is connected to the condenser 2 by the high-side refrigerant automatic expansion valve 5.
Depressurize the high pressure refrigerant liquid from. The reduced pressure low-pressure refrigerant liquid is supplied to the low-source-side refrigerant condenser 6 that also functions as the high-source-side evaporator, and the low-source-side high-pressure gas from the low-source-side high-pressure gas pipe 20 is liquefied. It exchanges heat with the low-side high-pressure gas to become the high-side low-pressure gas. The low-source-side high-pressure refrigerant liquid liquefied by the low-source-side refrigerant condenser 6 also serving as the high-source-side evaporator is stored in the low-source-side refrigerant receiver 7. Then, this high-source side low-pressure gas is sucked from the intake port of the high-source side compressor 1, becomes high-source side high-pressure gas in the high-source side compressor 1, is discharged to the high-source side high-pressure gas pipe 27, and is binary frozen. It constitutes the high temperature side cycle of the device.

The low-source side high-pressure gas pipe 21 from the discharge port of the low-source side compressor 28 is connected to the low-source side high-pressure gas pipe 20 via the low-source side high-pressure oil separator 15. The low-source side refrigerant liquid pipe 26 liquefies the low-source side refrigerant liquid liquefied in the low-source side refrigerant liquid receiver 7 and collects it in the low-source side refrigerant liquid pipe 26.
It is supplied to the low-source side evaporator 18 provided with a blower 19 via 7. Then, the low-source side refrigerant liquid is supplied to the low-source side automatic expansion valve 17
Is reduced in pressure by the low-source side evaporator 18 and becomes low-source-side low-pressure gas.
Is inhaled into the intake port of. The sucked low-source side low-pressure gas becomes low-source side high-pressure gas in the low-source side compressor 28, and is discharged from the discharge port to the low-source side high-pressure gas pipe 21 to form a low-temperature side cycle of the dual refrigeration system. It is a thing.

Refrigerating machine oil discharged from the discharge port of the low-pressure side compressor 28 to the low-pressure side high-pressure gas pipe 21 is separated by the low-pressure side high-pressure oil separator 15, passes through the float valve 16, and returns to the oil return pipe 22. Is returned to the crankcase of the low-side compressor 28. However, a part of the oil enters the low-level side refrigerant condenser 6, flows into the low-level side refrigerant receiver 7 together with the condensed refrigerant liquid, and floats above the condensed refrigerant liquid in the liquid receiver 7. Stay in the state.

The floating state of the refrigerating machine oil in the low-side refrigerant receiver 7 is confirmed through a peep window 8 provided in the low-side refrigerant receiver 7, and accumulated in the low-side refrigerant receiver 7. The respective stop valves 91 of the oil drain pipe 9 installed according to the position of the oil to be opened are introduced to the low-side refrigerant / oil mixed liquid pipe 25. Then, the mixed liquid pipe 25 is provided in the low-pressure side high-pressure gas pipe 20, and the high-pressure / high-temperature low-source side gas from the low-source side compressor 28 and the refrigerant / oil mixed liquid of the low-source side refrigerant / oil mixed liquid pipe. Is connected to the heat transfer pipe inlet 101 of the liquid / gas heat exchanger 10 for exchanging heat via the low-side oil recovery automatic expansion valve 11.

Heat transfer tube outlet 1 of the liquid / gas heat exchanger 10
02 is provided with a low-source-side low-pressure oil separator 12, and this separator 12
The oil return pipe 24 connects the crankcase of the low-side compressor 28 via the float valve 13 of FIG. The low-pressure side suction pipe 29 of the low-pressure side compressor 28 is connected to the gas return pipe 23 of the low-pressure side low pressure oil separator 12 via the liquid / gas heat exchanger evaporation pressure adjusting valve 14.

When using this, the refrigerating machine oil discharged from the low-source side high-pressure gas pipe 21 together with the refrigerant gas R23 from the low-source side compressor 28 is separated by the low-source side high-pressure oil separator 15 and crankcase. Returned to. However, some of the oil passes through the oil separator 15 and enters the low-level side refrigerant condenser 6 together with the refrigerant, and flows into the low-level side refrigerant receiver 7 together with the condensed refrigerant, and the condensed refrigerant liquid Remains floating above.

Looking at this floating state through the sight window 8, the stop valve 91 is opened as appropriate, and the amount of the refrigerant flowing into the heat transfer tube inlet 101 of the liquid / gas heat exchanger 10 is determined by the amount in the liquid / gas heat exchanger 10. Low expansion oil recovery automatic expansion valve 1 that is adjusted according to the amount of evaporation
1 to the liquid / gas heat exchanger 10. Then, the refrigerant is evaporated in the liquid / gas heat exchanger 10 to separate the refrigerant and the oil in the low-pressure side low-pressure oil separator 12, and the refrigerant passes through the gas return pipe 23 and then the low-pressure side compressor 28. The side suction pipe 29 is inhaled.

The oil remaining after separating the refrigerant is the low-pressure side compressor 2.
Although it is returned to the crankcase of No. 8, in the ultra-low temperature refrigeration of the dual refrigeration system, the evaporation temperature is extremely low, and the remaining oil does not flow as it is. Therefore, in the present invention, the low pressure side low pressure oil separator 12 and the low pressure side suction pipe 29 of the low pressure side compressor 28 are used.
Since the evaporation pressure adjusting valve 14 for the liquid / gas heat exchanger is provided between the two, the separated oil smoothly flows into the low pressure side low pressure oil separator 12. And this low-source side low-pressure oil separator 12
It was confirmed that when a certain amount of the separated oil was accumulated, the float valve 13 automatically returned to the crankcase of the low-side compressor 28, and the oil return operation could be performed without stopping the low-side compressor 28. .

[0024]

According to the present invention, the oil retained in the low temperature side refrigerant receiver 7 in the low temperature side cycle can be partially removed from the surrounding oil without stopping the operation of the dual refrigeration system. Withdraw the refrigerant liquid. Then, the low-pressure side compressor 2 is passed through the liquid / gas heat exchanger 10 via the low-pressure side oil recovery automatic expansion valve 11.
The heat can be exchanged with the discharge gas of No. 8 to continuously separate the oil and return it to the low-pressure side compressor 28.

Therefore, the low-source side compressor 28 is prevented from running out of oil, continuous operation is possible, and oil is prevented from flowing into the low-source side evaporator 18 in advance. The cooling effect can be enhanced. As a result, many remarkable effects such as resource saving, energy saving, and labor saving can be obtained.

[Brief description of drawings]

FIG. 1 is a piping system diagram of an oil returning device from a low-source side refrigerant receiver in a dual refrigeration system of the present invention.

[Explanation of symbols]

 1 High-end side compressor 2 High-end side refrigerant condenser 3 Blower 4 High-end side oil separator 5 High-end side refrigerant automatic expansion valve 6 Low-end side refrigerant condenser 7 Low-end side refrigerant receiver 8 Peep window 9 Oil Vent pipe 91 Stop valve 10 Liquid / gas heat exchanger 101 Heat transfer pipe inlet 102 Heat transfer pipe outlet 11 Low source side oil recovery automatic expansion valve 12 Low source side low pressure oil separator 13 Float valve 14 Liquid / gas heat exchanger evaporation pressure Regulator valve 15 Low-source side high-pressure oil separator 16 Float valve 17 Low-source side automatic expansion valve 18 Low-source side evaporator 19 Blower 20, 21 Low-source side high pressure gas pipe 22 Oil return pipe 23 Gas return pipe 24 Oil return pipe 25 Low source side refrigerant / oil mixed liquid pipe 26 Low source side refrigerant liquid pipe 27 High source side high pressure gas pipe 28 Low source side compressor 29 Low source side suction pipe

Claims (2)

[Claims] 1. In a low temperature side cycle of a dual refrigeration system, refrigerating machine oil that is separated into two layers from the refrigerant liquid in the low source side refrigerant receiver 7 and stays is withdrawn along with the surrounding refrigerant liquid, The pressure is reduced and heat is exchanged with the discharge gas of the low-pressure side compressor 28, and the mixed refrigerant liquid is vaporized and separated, and the refrigerant gas is returned to the gas suction side of the low-pressure side low-pressure compressor 28, The evaporation pressure is adjusted between the low-pressure oil separator 12 and the low-pressure side compressor 28 to keep the evaporation pressure and temperature in the liquid / gas heat exchanger 10 and the low-pressure side low-pressure oil separator 12 constant. A method for returning oil from a receiver in a low-temperature cycle of a dual refrigeration system, characterized in that the temperature of the refrigerating machine oil is maintained above its pour point and returned to the crankcase of the low-source side compressor 28. . 2. In the low temperature side cycle of the dual refrigeration system, the low side high pressure oil separator 1 on the discharge side of the low side compressor 28.
5 and the low-side refrigerant condenser 6, a liquid / gas heat exchanger 10 is interposed, and a plurality of oil drain pipes 9 provided with stop valves 91 from the low-side refrigerant receiver 7 are attached to the low-side side. The automatic expansion valve for oil recovery 11 is interposed to connect with the heat transfer tube inlet of the liquid / gas heat exchanger 10, and the tube from this heat transfer tube outlet is connected to a separate low-pressure side low-pressure oil separator 12. The float valve in the lower part of the low-pressure side low-pressure oil separator 12 is connected to the pipe to the crankcase of the low-pressure side compressor 28, and the gas outlet of this low-pressure side low-pressure oil separator 12 and the compressor low-pressure side suction An oil return device from a liquid receiver in a low temperature cycle of a dual refrigeration system, which is connected to a pipe 29 through an evaporation pressure adjusting valve 14 for a liquid / gas heat exchanger.