JPS595814B2 - Two-stage compression refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a two-stage compression refrigeration system equipped with a defrosting circuit.

First, a conventional two-stage compression refrigeration system will be explained with reference to FIG.

In the figure, 1 is a two-stage compression device equipped with a low-stage compressor 2 and a high-stage compressor 3, 4 is a condenser whose one end is connected to the discharge side of the high-stage compressor 3, and 5 is one end. is a liquid reservoir connected to the other end of the condenser 4, and 6 is an intercooler, one end of which is connected to the other end of the liquid reservoir 5 through a throttle device 7 of the intermediate circuit and an on-off valve 8 of the intermediate circuit. One end and the other end are connected to the suction side of the high-stage compressor 3, respectively.

Further, one end of the cooled portion of the intercooler 6 is connected to the other end of the liquid reservoir 5 via an on-off valve 9 of the cooling circuit.

Reference numeral 10 indicates a throttle device of a cooling circuit whose one end is connected to the other end of the cooled portion of the intercooler 6, and reference numeral 11 indicates a throttle device whose one end is connected to the other end of the throttle device 10 of the cooling circuit and the discharge side of the high-stage compressor 3. The connected cooler 12 is an accumulator 13 whose one end is connected to the other end of the cooler 11 and the other end is connected to the suction side of the low stage compressor 2.
1 is a defrosting circuit opening/closing valve provided between the discharge side of the high-stage compressor 3 and the cooler 11, 14 is a condenser blower, and 15 is a cooler blower.

Reference numeral 100 denotes a cooling circuit, starting from the discharge side of the high-stage compressor 3, including a condenser 4, a liquid reservoir 5, a cooling circuit opening/closing valve 9, an intercooler 6, a cooling circuit throttling device 10, a cooler 11, and It consists of a circuit that extends through the accumulator 12 to the suction side of the low-stage compressor 2.

Reference numeral 200 denotes an intermediate circuit, which branches off from the outlet side of the liquid reservoir 5 of the cooling circuit 100 and passes through the intermediate circuit on-off valve 8, the intermediate circuit throttling device 7, and the intercooler 6 to supply the suction to the high-stage compressor 3. It consists of a circuit that goes to the side.

Reference numeral 300 denotes a defrosting circuit, which is comprised of a circuit that extends from the discharge side of the high-stage compressor 3 to the suction side of the low-stage compressor 2 via the defrosting circuit on-off valve 13, cooler 11, and accumulator 12. ing.

With this configuration, during cooling operation,
The cooling circuit on-off valve 9 and the intermediate circuit on-off valve 8 are opened, the defrosting circuit on-off valve 13 is closed, and refrigerant is supplied to the cooling circuit 100 and the intermediate circuit 200.

That is, the refrigerant is circulated as shown by the solid line arrows in FIG.

Then, during defrosting operation, the on-off valve 9 of the cooling circuit is closed,
The defrosting circuit on-off valve 13 and the intermediate circuit on-off valve 8 are opened to supply refrigerant to the defrosting circuit 300 and the intermediate circuit 200.

That is, the refrigerant is circulated as indicated by the broken line arrows in FIG.

In this way, during normal cooling operation and defrosting operation, the refrigerant is also circulated in the intermediate circuit 200 to prevent the temperature of the refrigerant gas discharged from the high-stage compressor 3, the motor temperature, the oil temperature, etc. from rising. being done.

. However, during defrosting operation, since the amount of refrigerant gas supplied to the condenser 4 is small, the condensing capacity of the condenser 4 becomes more than necessary relative to the amount of refrigerant gas, and in particular, air cooling using the condenser blower 14 In the condensing device, the amount of refrigerant increases significantly when the outside temperature is low, so a large amount of refrigerant liquid accumulates in the liquid reservoir 5, and the amount of refrigerant circulating through the defrosting circuit 300 becomes insufficient, causing the cooling The amount of heating at 11 is reduced.

Therefore, the defrosting ability is extremely reduced, and the operating efficiency is deteriorated, such as requiring long hours of operation for defrosting.

Since the refrigerant liquid is accumulated in the liquid reservoir 5 one after another, the amount of refrigerant circulated through the intermediate circuit 200 during the defrosting operation also becomes insufficient.

Therefore, the discharge refrigerant gas temperature, motor temperature, oil temperature, etc. of the high-stage compressor 3 are increased, and various protection devices installed in the refrigerant circuit are activated to stop the defrosting operation, resulting in stable defrosting. There were drawbacks such as the inability to drive.

Further, during the defrosting operation, the refrigerant liquid that is condensed by heating the cooler 11 is supplied to the accumulator 12 and accumulated therein.

Therefore, when the amount of frost is large and a relatively long defrosting operation is performed, the amount of refrigerant liquid accumulated in the accumulator 12 increases, and the refrigerant liquid is supplied to the suction side of the low-stage compressor 2. There was also the drawback of liquid back-up operation.

This invention has been made to eliminate the above-mentioned drawbacks.

An embodiment of the present invention will be described below with reference to FIG.

In this figure, parts with the same reference numerals as in FIG. 1 are the same as or correspond to those in FIG. 1.

Reference numeral 16 denotes a three-way valve which is a circuit switching device, and is provided at a branch part of a circuit that connects the discharge side of the high-stage compressor 3 to the condenser 4 and the cooler 11, respectively. It is configured to close the circuit.

17 is a heat exchanger provided in the accumulator 12, one end of which is connected to the circuit connecting the three-way valve 16 and the cooler 11, and the other end connected to the circuit connecting the three-way valve 16 and the cooler 11; It is connected to the throttle device 7.

100 is a three-way valve 1 from the discharge side of the high-stage compressor 3.
6 and the condenser 4, etc., to the suction side of the low-stage compressor 2, 200 is an intermediate circuit, and 300 is a cooling circuit from the discharge side of the high-stage compressor 3 through the three-way valve 16, the cooler 11, etc. A defrosting circuit 400 leads to the suction side of the stage side compressor 2, which branches from between the three-way valve 16 and the cooler 11 of the defrosting circuit 300, passes through the heat exchanger 17 and the throttling device 7, and connects to the high stage compressor. This is an intermediate circuit for defrosting that leads to the suction side of No. 3.

Note that other parts are the same as those shown in FIG. 1, so explanations will be omitted.

Next, the action will be explained.

During cooling operation, the three-way valve 16 is controlled to close the cooling circuit 100.
side, and at the same time open the cooling circuit on-off valve 9 and the intermediate circuit on-off valve 8 to open the cooling circuit 100 and the intermediate circuit 200.
and supply refrigerant.

That is, the refrigerant is circulated as indicated by the solid line arrows in FIG.

Therefore, the refrigerant gas discharged from the discharge side of the high-stage compressor 3 is condensed in the condenser 4 and becomes a refrigerant liquid, which is accumulated in the liquid reservoir 5.

The water is then divided into the cooling circuit 100 and the intermediate circuit 200.

The refrigerant liquid flowing through the cooling circuit 100 is supercooled in the intercooler 6, and is depressurized in the cooling circuit throttling device 10.
1, the object to be cooled is cooled and evaporated, passed through an accumulator 12, and sucked into the suction side of the low-stage compressor 2, where it is compressed.

On the other hand, the refrigerant liquid flowing through the intermediate circuit 200 is depressurized by the throttle device 7 of the intermediate circuit, and is evaporated by exchanging heat with the refrigerant liquid flowing through the cooling circuit 100 in the intercooler 6, and is then evaporated on the suction side of the high-stage compressor 3. This prevents increases in the temperature of the refrigerant gas discharged from the high-stage compressor 3, the motor temperature, the oil temperature, etc.

In addition, during defrosting operation, the three-way valve 16 is controlled to open the defrosting circuit 300 side, and at the same time, the cooling circuit on-off valve 9 and the intermediate circuit on-off valve 8 are closed, so that the defrosting circuit 300 and the defrosting circuit 300 are closed. Refrigerant is supplied to the intermediate circuit 400.

That is, the refrigerant is circulated as indicated by the broken line arrow in FIG.

Therefore, the refrigerant gas discharged from the discharge side of the high-stage compressor 3 is divided into the defrosting circuit 300 and the intermediate circuit 400 for defrosting.

The refrigerant gas flowing through the defrosting circuit 300 heats the cooler 11 to defrost it, passes through the accumulator 12, is sucked into the suction side of the low-stage compressor 2, and is compressed.

On the other hand, the refrigerant gas flowing through the intermediate circuit 400 for defrosting is supplied to the heat exchanger 17, where the refrigerant liquid accumulated in the accumulator 12 is heated and evaporated, so that a part of the refrigerant gas becomes refrigerant liquid, and the expansion device 7 The gas is depressurized and evaporated, and is sucked into the suction side of the high-stage compressor 3, thereby preventing increases in the discharge gas temperature, motor temperature, oil temperature, etc. of the high-stage compressor 3.

As described above, according to the present invention, the cooling circuit, the defrosting circuit, and the intermediate circuit for defrosting are provided, and the defrosting circuit and the intermediate circuit for defrosting are provided without supplying refrigerant to the cooling circuit during defrosting. Since the refrigerant is supplied to the refrigerant, the refrigerant liquid does not accumulate in the liquid reservoir during defrosting operation.

Therefore, the amount of refrigerant circulated through the defrosting circuit can be maintained appropriately, and defrosting performance can be maintained without deterioration and defrosting operation with high operational efficiency can be performed.

Since the refrigerant is supplied to the high-stage compressor through the intermediate circuit for defrosting, it is possible to prevent the discharge gas temperature, motor temperature, oil temperature, etc. of the high-stage compressor from rising. Stable defrosting operation is possible.

In addition, the heat exchanger provided in the intermediate circuit for defrosting prevents a large amount of refrigerant liquid from accumulating in the accumulator, thereby preventing liquid back-up operation in which refrigerant liquid is supplied to the lower stage compressor. be able to.

Furthermore, there is a method of providing an intermediate diaphragm device for defrosting in the intermediate circuit for defrosting, separately from the diaphragm device 7 of the intermediate circuit, but in this case, two diaphragm devices for the intermediate circuit are required, resulting in high cost. However, in this invention, the diaphragm device for the intermediate circuit for defrosting and the diaphragm device for the intermediate circuit for cooling are both used, so there is only one diaphragm device for the intermediate circuit. It is possible to obtain a two-stage compression refrigeration system that requires only one unit, is low in cost, and has high reliability.

In addition, in the above embodiment, an air-cooled condensing device using a condenser blower is described as a condensing device, but
Other condensing devices such as a water-cooled condensing device may be used, and similar effects can be obtained without necessarily providing a liquid reservoir or an intercooler.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant circuit diagram showing a conventional two-stage compression refrigeration system, and FIG. 2 is a refrigerant circuit diagram of a two-stage compression refrigeration system showing an embodiment of the present invention. In the figure, 1 is a two-stage compression device, 4 is a condenser, 7 is an intermediate circuit throttle device, 11 is a cooler, 12 is an accumulator, and 16 is a condenser.
is a three-way valve, 17 is a heat exchanger, 100 is a cooling circuit, 200
300 is an intermediate circuit, 300 is a defrosting circuit, and 400 is an intermediate circuit for defrosting. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A cooling circuit formed by sequentially communicating a two-stage compression device having a low-stage compressor and a high-stage compressor, a condenser, a throttle device, a cooler, and an accumulator, the two-stage compression device, the cooler, and a defrosting circuit that connects the accumulators in sequence; a circuit switching device that switches between the cooling circuit and the defrosting circuit; and when the cooling circuit operates, a part of the refrigerant liquid from the condenser is throttled. An intermediate circuit that supplies electricity to the suction side of the high-stage compressor through the device, branches from between the circuit switching device and the cooler, passes through a heat exchanger installed in the accumulator, and then connects to the throttle of the intermediate circuit. A defrosting intermediate circuit connected to the inlet side of the device is provided, and during defrosting operation, the circuit switching device is switched and controlled to supply refrigerant to the defrosting circuit and the defrosting intermediate circuit. A two-stage compression refrigeration device characterized by: