JPH02166355A - Low temperature freezer and operation therefor - Google Patents

Abstract

PURPOSE:To perform a stable and superior energization of a compressor without having any overload operation by a method wherein a refrigerant feeding pipe at a discharging side of the compressor and a refrigerant returning pipe at a suction side of the compressor are communicated to each other by a bypassing pipe. CONSTITUTION:Mixed refrigerant is adiabatically compressed by a compressor 1, the thermal insulated refrigerant is cooled with cooling water at a condensor 2 and partially condensed. The gas-liquid mixed refrigerant heat exchanged with the returned refrigerant from a low temperature part at an auxiliary heat exchanger 3 and further partially condensed, thereafter it is separated into a condensed refrigerant and a non-condensed refrigerant by a first separator 4. The separated and condensed refrigerants are adiabatically expanded by a first expansion valve 5 to generate a low temperature and merged into the returned refrigerant from the low temperature part. The refrigerants are made to flow to the first heat exchanger 6 to cool the non-condensed refrigerant separated by the first separator and partially condense them. A sequential repetition of this operation causes a refrigerant of low boiling point to he condensed and further to be adiabatically expanded, thereby a refrigerant gas of lower temperature is produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a refrigerator using a compressor, and particularly to a refrigerator for obtaining a low temperature using a plurality of non-azeotropic mixed refrigerants, and a method for operating the same. .

[Conventional technology]

In a known single-stage refrigeration system, refrigerant vapor is compressed, this refrigerant vapor condenses by exchanging heat with surrounding air or water, and this condensate is adjusted to a low pressure by an expansion valve and expands adiabatically. , generates a refrigeration effect, and finally returns to the compressor.

Such systems are limited to obtaining temperatures as low as -60°C.

In addition, in the multi-component cascade psych, which is known as a low-temperature refrigeration system, a desired low temperature can be obtained by using a single component refrigerant and combining refrigeration psychs μ in multiple stages. On the other hand, in the mixed refrigerant refrigeration system μ, a low temperature can be obtained by liquefying and separating the mixed refrigerant stepwise in the order of high boiling points, sequentially condensing the low boiling point refrigerant, and adiabatically expanding the refrigerant.

The above mixed refrigerant refrigeration cycle will be explained using FIG. 3. In Figure 3, the mixed refrigerant is adiabatically compressed by the compressor (■), this adiabatic refrigerant is cooled with cooling water etc. in the condenser (■), and partially condensed, and this gas-liquid mixed refrigerant is transferred to the auxiliary heat exchanger (■). After exchanging heat with the refrigerant returned from the low-temperature section and further partially condensing it, the refrigerant is separated into condensed refrigerant and uncondensed refrigerant in the first separator (2). The separated condensed refrigerant is adiabatically expanded in the first expansion valve (■) to generate a low temperature, merged with the refrigerant returned from the low-temperature section, passed through the first heat exchanger (■), and separated in the first separator. The uncondensed refrigerant is further cooled and partially condensed. By successively turning this over, the refrigerants with lower boiling points are condensed, and by adiabatically expanding this, it is possible to generate refrigerated gas at a much lower temperature.

[Problem to be solved by the invention]

As described above, in the mixed refrigerant refrigeration system, there is a large difference between the pressure in each part of the refrigerator when the refrigerator is started and the pressure in each part of the refrigerator in a steady state.

In the steady state, each low temperature section is maintained at a predetermined low temperature state, and the refrigerant is partially condensed, so the pressure inside the machine is kept low. On the other hand, at startup, the refrigerant temperature is close to room temperature and the amount of condensation is small, so the compressor discharge pressure in particular becomes extremely high. Therefore, a heavy load is placed on the compressor, and the operation of the compressor may have to be stopped. Conversely, if the compressor discharge pressure at startup is kept low, the internal pressure will drop as the refrigeration cycle progresses, making it impossible to condense the desired refrigerant.

In order to obtain refrigerant at a very low temperature, it is necessary to keep the compressor discharge pressure low at startup, and to maintain a predetermined discharge pressure during normal operation.

In order to lower the compressor discharge pressure when the refrigerator is started, it is effective to lower the average internal pressure when the refrigerator is stopped. In order to lower the average internal pressure when the refrigerator is stopped, the method of increasing the volume of the compressor suction side (low pressure side during operation) is to increase the reed, refrigerant return piping, and flow area on the return side of the heat exchanger. Alternatively, a cushion tank for refrigerant storage is provided and connected to the refrigerant return piping on the compressor suction side with a thin tube.

When the flow path area on the ευ side of the refrigerant return piping and refrigerant of the heat exchanger increases, the refrigerant gas flow rate changes, so there is a design limit. Although the required volume of the cushion tank is determined by consideration, it has the disadvantage of requiring a very large volume.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a refrigerator and a method for operating the same, which are free from the above-mentioned drawbacks and can reduce the average internal pressure by simple means.

[Failure to solve the problem]

As a result of intensive research, the present inventors have discovered that the above object can be achieved by providing a bypass pipe that communicates the refrigerant feed pipe on the compressor discharge side with the refrigerant collection pipe on the compressor suction side. , completed the invention.

That is, the present invention includes a compressor, a condenser, an evaporator, a plurality of intermediate heat exchangers through which refrigerant sent from the compressor discharge side and refrigerant returned from the evaporator flow, a plurality of separators, and a pressure reducer. A plurality of non-azeotropic mixed refrigerants are used as the refrigerant, and the refrigerant condensed from the refrigerant that has passed through the separator is combined with the refrigerant returned from the evaporator into the intermediate heat exchanger via the pressure reducer, In the refrigerating machine that obtains a low temperature by means of cooling uncondensed refrigerant in the refrigerant and sequentially condensing the refrigerant with a lower boiling point, and means of circulating the refrigerant to the evaporator via a final stage or intermediate pressure reducer, the compressor The refrigerator is characterized in that a bypass pipe is provided that communicates from a refrigerant discharge pipe on the machine discharge side to a refrigerant suction pipe on the compressor suction side.

Further, the present invention provides a compressor, a condenser, an evaporator, a plurality of intermediate heat exchangers through which refrigerant sent from the compressor discharge side and a refrigerant from the evaporator flow, a plurality of separators, and a pressure reducer. ), a plurality of non-azeotropic mixed refrigerants are used as the refrigerant, and the refrigerant condensed from the refrigerant that has passed through the separator is combined with the refrigerant returned from the evaporator into the intermediate heat exchanger via the pressure reducer. At least, the uncondensed refrigerant in the refrigerant is cooled, the refrigerant with a lower boiling point is sequentially condensed, and the refrigerant is passed through the final stage or intermediate pressure reducer to the evaporator to create a low temperature, and the compression In a method of operating a refrigerator in which a bypass pipe is provided that communicates from a refrigerant discharge pipe on the machine discharge side to a refrigerant suction pipe on the compressor suction side, and an on-off valve is provided in the bypass pipe, the discharge pressure or suction pressure of the compressor is Alternatively, there is also a method for operating a refrigerator, characterized in that the refrigerant temperature on the discharge side of the compressor is detected, or the on-off valve is opened and closed by a timer without using any detectors.

In the bypass piping of the present invention, if the refrigerant outlet on the compressor discharge side is provided after passing through the condenser, the refrigerant will have a cooling effect,
This is preferable since it has the effect of suppressing the rise in refrigerant temperature on the discharge side of the compressor.

Furthermore, in the method for operating a refrigerator according to the present invention, an on-off valve is provided in the bypass pipe, and the on-off valve is opened and closed according to the operating specifications of the compressor, thereby controlling the discharge pressure of the compressor. The discharge pressure or suction pressure and the discharge side refrigerant temperature are detected as detection items of the operating specifications of the compressor, and the opening/closing valve is opened and closed to operate the refrigerator. Furthermore, if the operating specifications of the compressor at startup are measured, the refrigerating machine can be operated by opening and closing the on-off valve using a timer.

[Effect]

When the bypass pipe is provided, the amount of refrigerant circulated is reduced by the amount passing through the bypass pipe. At startup, the difference between the discharge pressure and suction pressure of the compressor is very large, and the amount of refrigerant passing through the bypass pipe is large, but as the steady state approaches, the compressor discharge pressure decreases and the refrigerant The amount of passage through the bypass pipe also becomes smaller. Therefore, by selecting a compressor that takes into account the amount of refrigerant that passes through the bypass pipe in order to ensure the amount of refrigerant circulating necessary for the refrigeration cycle, a large amount of refrigerant can pass through the bypass pipe at startup, and the compressor discharge pressure will decrease. It has a large reduction effect. And as driving progresses,
Refrigerant condensation in the heat exchanger inside the machine progresses, the pressure inside the machine gradually decreases, and the loss of circulation amount due to refrigerant passing through bypass piping also decreases. By providing the bypass piping as described above, the compressor can be started safely and without overload, and the refrigerator can be operated to ensure refrigerant circulation even in a steady state. Can be done.

Next, by providing an on-off valve in the bypass pipe,
The on-off valve of the bypass pipe can be opened and closed by a pressure switch that detects the discharge pressure of the compressor. When the compressor discharge pressure is high at startup, the on-off valve of the bypass piping is opened to suppress the increase in discharge pressure. As the operation of the refrigerator progresses, the amount of refrigerant condensed in each heat exchanger increases, causing the pressure inside the refrigerator to decrease. When the discharge pressure of the compressor becomes lower than a predetermined pressure, the on-off valve of the bypass pipe is closed. By detecting the compressor discharge pressure in this manner, the compressor can be started safely. Furthermore, the opening and closing operations of the on-off valve can be controlled by detecting not only the discharge pressure of the compressor but also the temperature of the refrigerant on the discharge side of the compressor.

In order to create a low-temperature refrigerant below -100°C using several types of non-azeotropic mixed refrigerants, the discharge pressure of the compressor at startup may be approximately twice the discharge pressure during steady operation. The significance of using bypass piping is significant.

〔Example〕

Examples of the present invention will be described below with reference to the drawings, but the present invention is not limited to these examples.

Example 1 FIG. 1 is a route diagram showing one embodiment of the present invention.

In Fig. 1, a mixed refrigerant is adiabatically compressed by a compressor (2), this adiabatic refrigerant is cooled by cooling water etc. in a condenser (2), and partially condensed, and this gas-liquid mixed refrigerant is transferred to an auxiliary heat exchanger (2). After exchanging heat with the refrigerant returned from the low-temperature section and further partially condensing it, the refrigerant is separated into condensed refrigerant and uncondensed refrigerant in the first separator (2). The separated condensed refrigerant is adiabatically expanded in the first expansion valve (■) to generate a low temperature, merged with the refrigerant returned from the low-temperature section, passed through the first heat exchanger (■), and separated in the first separator. The uncondensed refrigerant is further cooled and partially condensed. By sequentially turning this over, refrigerants with lower boiling points are condensed, and by adiabatically expanding the refrigerants, refrigerant gas at a much lower temperature can be generated.

In order to create a low-temperature refrigerant below -100°C using several types of non-azeotropic mixed refrigerants, the discharge pressure of the compressor during steady state is reduced to 1.
If the set pressure is 5 匈・S/eym"G, the compressor discharge pressure at startup will be 26 to 30 hours・5/α20. Compression is It is necessary to suppress the machine discharge pressure to 20 kg/amza or less.For this purpose, a bypass piping [phase] is provided.In order to set an appropriate refrigerant bypass flow rate, the bypass piping [phase] is a communicating pipe with an orifice installed. However, it is preferable to use a capillary tube.

Embodiment 2 FIG. 2 is a meridian diagram showing another embodiment of the present invention. FIG. 2 is an example in which an on-off valve is provided in the bypass pipe.

In FIG. 2, a bypass pipe @ is provided in which a solenoid valve 0 is attached to the bypass pipe shown in the first embodiment. The solenoid valve ◎ is opened and closed by the signal from the pressure switch [phase] that detects the compressor discharge pressure, and the refrigerator is started so that the compressor discharge pressure is within the specification value, or the operation corresponding to load fluctuations during normal operation is started. It becomes possible.

Furthermore, a temperature switch is provided to detect the temperature of the refrigerant discharged from the compressor, and when the temperature exceeds the set temperature, this solenoid valve ◎ is opened, which is effective in suppressing overheating of the refrigerant.

〔Effect of the invention〕

According to the invention, pie buff,! Il! By providing the pipe, the compressor can be started in a stable manner without overload, and the refrigerator can be operated to ensure refrigerant circulation even in a steady state.

[Brief explanation of the drawing]

1 and 2 are meridian diagrams showing an embodiment of the present invention, and FIG. 3 is a route diagram of a conventional refrigerator. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 3... Auxiliary heat exchanger, 4... First separator, 5... First expansion valve, 6...
- First heat exchanger, 7... Second separator, 8... Second expansion valve, 9... Second heat exchanger, 10... Third separator,
11...Third expansion valve, 12-...Third heat exchanger, 13
...Final stage expansion valve, 14... Evaporator, 16... Feed refrigerant, 17... Return refrigerant, 18...
・Bypass piping, 19... Solenoid valve, 20... Pressure switch Patent applicant Ebara Corporation

Claims (1)

[Claims] 1. A compressor, a condenser, an evaporator, a plurality of intermediate heat exchangers through which the refrigerant sent from the compressor discharge side and the refrigerant returned from the evaporator flow, a plurality of separators, and a depressurizer. The refrigerant is a mixture of multiple non-azeotropic refrigerants, and the condensed refrigerant that has passed through the separator is combined with the refrigerant returned from the evaporator into the intermediate heat exchanger via the pressure reducer. In a refrigerator that obtains a low temperature by means of cooling the uncondensed refrigerant in the refrigerant and sequentially condensing the refrigerant with a lower boiling point, and means of circulating the refrigerant to the evaporator via a final stage or intermediate pressure reducer, A refrigerator comprising a bypass pipe that communicates from a refrigerant discharge pipe on the compressor discharge side to a refrigerant suction pipe on the compressor suction side. 2. The refrigerator according to claim 1, wherein the bypass pipe is provided with an on-off valve. 3. Equipped with a compressor, a condenser, an evaporator, a plurality of intermediate heat exchangers through which refrigerant sent from the compressor discharge side and refrigerant returned from the evaporator flow, a plurality of separators and a pressure reducer. , a plurality of non-azeotropic mixed refrigerants are used as the refrigerant, and the refrigerant condensed from the refrigerant that has passed through the separator is combined with the refrigerant returned from the evaporator through the pressure reducer to combine with the refrigerant returned from the evaporator. The uncondensed refrigerant is cooled, and the refrigerant with a lower boiling point is sequentially condensed, and the refrigerant is passed through the evaporator through the final stage or an intermediate pressure reducer to create a low temperature, and the refrigerant is discharged from the compressor discharge side. In a method of operating a refrigerator, in which a bypass pipe is provided that communicates from the pipe to a refrigerant suction pipe on the suction side of the compressor, and an on-off valve is provided in the bypass pipe, the discharge pressure or suction pressure of the compressor, or the discharge pressure of the compressor. A method for operating a refrigerator, characterized in that the on-off valve is opened and closed by detecting the side refrigerant temperature or by using a timer without using any detectors.