JPS5852148B2 - 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 with one end connected to the discharge side of the high-stage compressor 3, and 5 is a condenser with one end connected to the discharge side of the high-stage compressor 3. A liquid reservoir 6 connected to the other end of the condenser 4 is an intercooler, and one end of the cooling part 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. The other end is connected to the suction side of the high-stage compressor 3, and one end of the cooled part 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 portion of the intercooler 6; 11 is a cooling circuit throttle device whose one end is connected to the other end of the cooling circuit throttle device 10 and the discharge side of the high-stage compressor 3; The connected cooler 12 is an accumulator 1 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.
3 is an on-off valve for a defrosting circuit provided between the discharge side of the high-stage compressor 3 and the cooler 11; 14 is a condenser blower; 15
is a cooler blower.

100 is a cooling circuit, which includes a condenser 4 on the discharge side of the high-stage compressor 3, a liquid reservoir 5, an on-off valve 9 for the cooling circuit, an intercooler 6, a throttle device 10 for the cooling circuit, 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 that runs from the discharge side of the high-stage compressor 3 to the suction side of the low-stage compressor 2 via the defrosting circuit's on-off valve 13, the cooler 11, and the accumulator 12. has been done.

In the device configured in this way, 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 the cooling circuit 100 and the intermediate circuit 200 are connected. supply refrigerant to.

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 circulated through the defrosting circuit 300 is insufficient, causing the cooler 11 to become overheated. The amount of heating 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 there is a large amount of frost 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 was made in order to eliminate the above-mentioned drawbacks. During defrosting operation, refrigerant is not supplied to the condenser, but instead is branched from the defrost circuit and sent to the high temperature via the heat exchanger in the accumulator. The refrigerant is supplied to the circuit leading to the suction side of the stage side compressor.

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

In the figure, parts with the same reference numerals as in Figure 1 are numbered 1.
Reference numeral 16, which is the same or equivalent part in the figure, is a three-way valve that is an open circuit switching device, and is installed at a branch part of the circuit that connects the discharge side of the high-stage compressor 3 to the condenser 4 and the cooler 11, respectively. The circuit is configured to open one of the circuits and close the other.

A heat exchanger 17 is provided in the accumulator, and one end thereof is connected to a circuit connecting the three-way valve 16 and the cooler 11.

Reference numeral 18 denotes a throttle device having one end connected to the other end of the heat exchanger 17 and the other end connected to the suction side of the high stage compressor 3.

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 of the defrosting circuit 300 and the cooler 11, passes through the heat exchanger 17 and the throttling device 18, and then connects to the high stage compressor. This is an intermediate circuit for defrosting that leads to the suction side of No. 3.

Note that explanations of other parts will be omitted.

Next, the effect 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.
The object to be cooled is cooled and evaporated in step 1, and
The air is drawn into the suction side of the low-stage compressor 2 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 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 1T, which heats and evaporates the refrigerant liquid accumulated in the accumulator 12, so that a part of the refrigerant gas becomes refrigerant liquid, and the expansion device 18 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 during defrosting, 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 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 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 can be performed.

Moreover, since the refrigerant liquid in the accumulator is heated and evaporated by the heat exchanger provided in the intermediate circuit for defrosting, a large amount of refrigerant liquid does not accumulate in the accumulator, Effects such as liquid backup operation in which refrigerant liquid is supplied to the lower stage compressor can be obtained.

In addition, in the above embodiment, an air-cooled condensing device using a condenser blower is described as a condensing device, but
Similar effects can be obtained using other condensing devices such as a water-cooled condensing device.

[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, 11 is a cooler,
12 is an accumulator, 16 is a three-way valve, 1T is a heat exchanger, 100 is a cooling 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. Two-stage compression device having a low-stage compressor and a high-stage compressor, a circuit switching device that switches and controls a refrigerant circuit between a cooling operation circuit and a defrosting operation circuit, a condenser, a throttle device, a cooler, and an accumulator. a cooling circuit in which the two-stage compression device, the circuit switching device, the cooler, and the accumulator are connected in sequence; a defrosting circuit in which the defrosting circuit has the circuit switching device and the cooler; and an intermediate circuit for defrosting which branches off from between and passes through a heat exchanger provided in the accumulator to the suction side of the high-stage compressor, and during defrosting operation, the circuit is switched. A two-stage compression refrigeration device, characterized in that the device is switched and controlled to supply refrigerant to the defrosting circuit and the intermediate circuit for defrosting.