JPH0678849B2 - Refrigeration equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a refrigerating apparatus for obtaining an ultralow temperature by using one compressor and a non-azeotropic mixed refrigerant.

[Conventional technology]

Conventionally, as a refrigerating apparatus for obtaining an ultralow temperature by using a non-azeotropic mixed refrigerant, a refrigerating apparatus having a structure shown in FIG. In this system, the non-azeotropic mixed refrigerant gas discharged from the compressor 1 is partially condensed in the first condenser 2 and then in the gas-liquid separator 3 into a liquid having a higher boiling point component and a gas having a lower boiling point component. After being separated, the liquid is decompressed in the diversion path by the second expansion valve 8, and then reaches the suction pipe line of the compressor 1 through the second evaporator 4 ″ of the inner pipe portion of the double pipe type cascade heat exchanger 4. On the other hand, the gas passes through the main refrigerant circuit through the second condenser 4 ′ forming the double-tube cascade heat exchanger 4, after decompressing at the first expansion valve 6 and generating ultra-low temperature at the first evaporator 7, A refrigeration cycle is formed by merging with the high boiling point component and then sucking it into the compressor 1. In such a refrigerating device, a mixture containing a large amount of a refrigerant that has a low boiling point and does not condense at room temperature, in addition to a refrigerant that condenses at room temperature. Since the refrigerant is used, the pressure in the refrigerant circuit rises, especially when starting up, so that it cannot be actually used, There is a drawback that the output pressure becomes abnormally high.The main cause of the abnormally high pressure is that the balance pressure at the time of stop is high, and therefore the compressor discharge amount immediately after start-up becomes very large. Since the 2 evaporator 4 ″ cannot obtain a sufficient cooling power due to the heat capacity of the members and the low boiling point refrigerant components do not stay sufficiently in the main refrigerant circuit, the pressure increase is further promoted.

[Problems to be solved]

An object of the present invention is to provide an ultra-low temperature refrigeration system which can suppress a pressure increase at the time of starting and can perform a safe pull-down operation.

[Means and Actions for Solving Problems]

The present invention particularly relates to a refrigerating apparatus of this type, in which an opening / closing valve is provided between the second condenser and the first expansion valve, and the opening / closing valve is closed at the time of starting the compressor to flow through the first expansion valve. Is stopped, and the suction pressure of the compressor is rapidly reduced by using only the second expansion valve in the diversion path as the expansion device, and when the temperature in the second evaporator also drops to a predetermined low temperature,
The opening / closing valve is opened. For this reason,
At startup, the amount of gas sucked into the compressor is limited to that retained in the first evaporator and that flowing in through the second expansion valve, so the pressure rise immediately after startup can be suppressed to a small level. Then, when the temperature in the second evaporator drops and the low boiling point component refrigerant condenses and liquefies into the second condenser, the circulating refrigerant changes its concentration to the high boiling point component side, and the high pressure decreases further. Can drive safely and achieve the intended purpose.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Compressor 1, first condenser 2, gas-liquid separator 3, second condenser 4 ',
The configuration including the first expansion valve 6, the first evaporator 7, the second expansion valve 8, and the second evaporator 4 ″ is the same as that of the conventional device of FIG. 1, and in the present invention, the main refrigerant circuit further includes Gas-liquid separator 3, second
A check valve 9 is provided between the condensers 4 ', and an opening / closing valve, for example, an electromagnetic valve 5 is provided between the second condenser 4'and the first expansion valve 6.

The operation of this refrigerant circuit is performed as follows. First, when the apparatus is activated, the solenoid valve 5 is closed. In this state, the refrigerant discharged from the compressor 1 is partially liquefied in the condenser 2 and separated in the gas-liquid separator 3 into a liquid having a high boiling point component and a gas having a low boiling point component. The liquid reaches the second evaporator 4 ″ through the second expansion valve 8 where it is cooled and then returned to the suction side of the compressor 1. The same circulation is repeated thereafter. As the cooling action of the second evaporator 4 ″ progresses, it is liquefied and stored in the second condenser 4 ′ through the check valve 9. Here, at the time of start-up, the refrigerant sucked into the compressor 1 is limited to the amount accumulated in the first evaporator 7 and the amount passed through the second expansion valve 8. Therefore, the high pressure increase immediately after the start can be suppressed to be small. . Further, the refrigerant circulating in the circuit rapidly contains a large amount of high-boiling components due to the retention of the low-boiling components in the second condenser, which facilitates the reduction of the high-pressure pressure and enables quick safe operation. . After that, the high pressure is sufficiently lowered and the outlet temperature of the second evaporator 4 ″ is also lowered to a predetermined temperature by a separate sensor (not shown), and the solenoid valve 5 is opened to start the steady operation. You can.
Here, after the steady operation, the solenoid valve 5 is closed at the same time as the compressor 1 is stopped or a little earlier than that, so that the check valve 9 and the solenoid valve 5 act to make the second condenser 4'in the steady operation.
The low-boiling-point refrigerant component retained in the can be sealed as it is, and the increase in high-pressure pressure at startup can be more effectively suppressed. By doing so, it is also possible to eliminate the need for installing an expansion tank, which is generally aimed at reducing the balance pressure when the operation is stopped. In addition, it is possible to speed up stabilization of the refrigerant concentration distribution in the refrigeration cycle during startup operation or ON-OFF operation.

As described above, according to the present embodiment, by stopping the operation of the first expansion valve, it is possible to suppress the increase in the high-pressure pressure at the time of startup, and further to store the low-boiling-point refrigerant component as a liquid in the second condenser. Thus, it is possible to promote the reduction of the high pressure. Further, by providing a check valve at the inlet of the second condenser, it is possible to eliminate the need for an expansion tank for lowering the balance pressure at the time of stop.

〔The invention's effect〕

According to the present invention, the high pressure increase at startup is suppressed to a small level,
It can be made to drive safely quickly.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a conventional refrigeration system. FIG. 2 is a circuit diagram of the refrigerating apparatus of the present invention. In the drawings, 1: compressor, 2: first condenser, 3: gas-liquid separator, 4: double-pipe cascade heat exchanger, 4 ′: second condenser, 4 ″: second evaporator, 5 : Solenoid valve, 6: First expansion valve, 7: First evaporator, 8: Second expansion valve, 9: Check valve.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-59-208355 (JP, A)

Claims (3)

[Claims] 1. A main refrigerant circuit in which a non-azeotropic mixed refrigerant is used and a compressor, a first condenser, a gas-liquid separator, a second condenser, a first expansion valve, and a first evaporator are sequentially connected in an annular pipe. A second expansion valve between the gas-liquid separator and the suction pipe line of the compressor, and a diversion path connecting the second evaporator in a heat exchangeable state with the second condenser. In the above, an on-off valve is provided in a pipe line connecting the second condenser and the first expansion valve, and the on-off valve is closed for a predetermined time after the compressor is activated to close the first
A refrigeration system characterized in that a flow of a refrigerant from an expansion valve toward the compressor is stopped. 2. The refrigerating apparatus according to claim 1, wherein a check valve is provided in a pipe line connecting the gas-liquid separator and the second condenser. 3. The refrigerating apparatus according to claim 2, wherein the on-off valve is closed at the same time as or slightly earlier than the stop of the compressor.