JPS595815B2 - 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, 4 is a condenser whose one end is connected to the discharge side of the high-stage compressor 3; 5 is a reservoir whose one end is connected to the other end of the condenser 4; and 6 is an intercooler, one end of the cooling section. is connected to the other end of the liquid reservoir 5 via the throttle device 7 of the intermediate circuit and the on-off valve 8 of the intermediate circuit, and the other end is 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.

10 is a cooling circuit throttle device whose one end is connected to the other end of the cooled part of the intercooler 6; 11 is a cooler whose one end is connected to the other end of the cooling circuit throttle device 10; and 12 is a cooling circuit whose one end is connected to the other end of the cooling circuit. At the other end of the container 11, there is an accumulator whose other end is connected to the suction side of the low-stage compressor 2; 13 is an on-off valve for a defrosting circuit whose one end is connected to the discharge side of the high-stage compressor 3; 14; A drain pan coil 15 is provided below the cooler 11 and has one end connected to the other end of the opening/closing valve 13 of the defrosting circuit and the other end is connected to one end of the cooler 11. A drain pan 16 is provided below the cooler 11 and is equipped with the drain pan coil 14. 1 is a drain outlet of the drain pan 150, 17 is a condenser blower, and 18 is a cooler blower.

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

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 extending 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 and drain pan coil 12.

With this configuration, during cooling operation,
The cooling circuit on-off valve 9 and the intermediate circuit on-off valve 3 are opened,
The opening/closing valve 13 of the defrosting circuit is closed to supply refrigerant 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. 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 successively accumulated in the liquid reservoir 5, 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.

In addition, since the refrigerant gas discharged from the high-stage compressor 3 is supplied to the cooler 11 after heating the drain pan coil 14, the heating power in the cooler 11 is weak, and defrosting takes a long time. There is a drawback that frost operation is required, and if the heating order is reversed and the cooler 11 is heated first, the drain pan coil 14
There were disadvantages such as the heating power in the drain pan 15 becoming weaker and the drain pan falling into the drain pan 15 freezing and making it impossible to drain water.

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 19 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, so that one of the valves is opened and the other is closed. It is configured to close the circuit.

20 is a drain pan coil which is an auxiliary heat exchanger,
One end is connected to a circuit connecting the three-way valve 19 and the cooler 11, and the other end is connected between the on-off valve 8 of the intermediate circuit 200 and the throttle device 7 of the intermediate circuit 200.

100 is a three-way valve 1 from the discharge side of the high-stage compressor 3.
9 and the condenser 4, etc., to the suction side of the low-stage compressor 2; 200, the intermediate circuit; A defrosting circuit 400 that reaches the suction side of the stage compressor 2 branches from between the three-way valve 19 of the defrosting circuit 300 and the cooler 11, passes through the drain pan coil 20 and the throttling device 1, and then connects to the high stage compressor 3. This is an intermediate circuit for defrosting that connects to the suction side.

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

Next, the effect will be explained.

During cooling operation, the three-way valve 19 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, and is sucked into the suction side of the low-stage compressor 2 via the accumulator 12 and 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 19 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 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 heats the drain pan 15 with the drain pan coil 20, and a portion of the refrigerant gas becomes a refrigerant liquid, which is depressurized and evaporated by the expansion device 7, and then flows to the suction side of the high-stage compressor 3. This prevents increases in the discharge gas temperature, motor temperature, oil temperature, etc. of the high-stage compressor 3.

In this way, the embodiment described above is provided with an intermediate circuit 400 for defrosting that branches from the defrosting circuit 300 and reaches the low pressure side of the high-stage compressor 3 via the drain pan coil 20, so that during defrosting operation, Since refrigerant gas is supplied to the defrosting circuit 300 and the intermediate circuit 400 for defrosting, the cooler 11 is heated and defrosted by the refrigerant gas flowing through the defrosting circuit 300. The drain pan coil 20 is heated by the refrigerant scum flowing through the intermediate circuit 400.

Therefore, the heating power of the cooler 11 and the drain pan coil 20 can be ensured, the cooler 11 can be defrosted in a relatively short time, and the drain pan 15 does not freeze.

As described above, according to the present invention, the cooling circuit, the defrosting circuit, and the intermediate circuit for defrosting are provided, and during the defrosting operation, the defrosting circuit and the intermediate circuit for defrosting are provided without supplying refrigerant to the cooling circuit. Since the refrigerant is supplied to the intermediate circuit, 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 refrigerant is supplied to the high-stage compressor via the auxiliary heat exchanger in the intermediate circuit for defrosting, increases in the discharge gas temperature, motor temperature, oil temperature, etc. of the high-stage compressor are prevented. This enables stable defrosting operation.

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 only one diaphragm device is used as the intermediate circuit. A low-cost, highly reliable two-stage compression refrigeration system can be obtained.

In the above embodiment, an air-cooled condensing device using a condenser blower 17 was described as a condensing device, but other types of condensing devices such as a water-cooled condensing device may be used, and liquid storage, intermediate cooling, etc. The same effect can be obtained even if the container is not necessarily provided.

[Brief explanation of drawings]

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, 20 is a drain pan coil, 1
9 is a three-way valve, 100 is a cooling circuit, 200 is an intermediate circuit, 3
00 is a defrosting circuit, and 400 is an intermediate circuit for defrosting. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A two-stage compression device having a low-stage compressor and a high-stage compressor, a cooling circuit formed by sequentially communicating a condenser, a throttle device, and a cooler, and the two-stage compression device and a defrosting circuit that communicates with the cooler; a circuit switching device that switches between the cooling circuit and the defrosting circuit; and when the cooling circuit operates, a portion of the refrigerant liquid from the condenser is An intermediate circuit that supplies electricity to the suction side of the high-stage compressor through a throttling device, and is branched from between the circuit switching device and the cooler, passes through an auxiliary heat exchanger, and then flows to the inlet side of the throttling device of the intermediate circuit. and a defrosting intermediate circuit connected to the defrosting circuit, 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 system featuring: 2. The two-stage compression refrigeration system according to claim 1, wherein the auxiliary heat exchanger is a Lareta drain pan coil installed below the cooler.