JPS627462B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to improvement of a refrigeration system, and in particular, a method for defrosting the evaporator by providing a hot gas bypass pipe from the discharge side of the compressor to the evaporator. This invention relates to a refrigeration system that uses hot gas.

(b) Conventional technology Conventionally, methods for defrosting refrigeration equipment using hot gas include a reverse cycle method in which the evaporator is used as a condenser and the hot gas discharged from the compressor is directly supplied to the evaporator, and A flow path switching valve is provided on the discharge side, and a hot gas bypass pipe is provided from this switching valve to bypass the condenser and reach the evaporator, and the gas discharged from the compressor is passed through the hot gas bypass pipe to the evaporator. There are hot gas bypass methods, etc.
These reverse cycle methods and hot gas bypass methods supply the gas discharged from the compressor directly to the evaporator, so they do not consume as much power as defrosting methods that use heater heating. This method has the advantage that the defrosting time can be shortened compared to the off-cycle defrosting method.

(c) Problems to be Solved by the Invention However, the above-mentioned reverse cycle method and hot gas bypass method simply utilize the heat sensitivity of the hot gas discharged from the compressor, so if there is a large amount of frost formation, There was a problem in that the refrigerant liquefied in the evaporator returned to the compressor as it was, causing a so-called liquid back phenomenon.

In addition, in order to solve this problem, we have removed the so-called thermobank system in which the discharge pipe between the compressor and condenser and the suction pipe between the compressor and evaporator are placed inside a heat storage tank for heat exchange. A frosting device has been devised. In this method, a heat storage tank is heated with hot gas discharged from a compressor during cooling operation, and during defrosting, the liquefied refrigerant in an evaporator is guided to the heat storage tank. By using this, the refrigerant that has been liquefied in the evaporator can be completely vaporized in the heat storage tank, which is effective in preventing liquid back-up.

However, all hot gas defrosting systems including the above-mentioned thermobank system have the following problems, and improvements are desired. In other words, in the defrosting method using hot gas, hot gas is suddenly supplied to the evaporator, which has been under cooling operation and has become cold, so at the beginning of defrosting operation, the hot gas liquefies and accumulates in the evaporator. However, as the amount of refrigerant returning to the compressor decreases, the low pressure decreases, and the high pressure side pressure also decreases.
There was a problem that the defrosting ability decreased.

The present invention was developed in view of these points, and has functions such as shortening the defrosting time by hot gas defrosting, preventing liquid back-up after defrosting by using a thermobank method, and further increasing the refrigerating capacity during recooling operation. The objective is to prevent hot gas from liquefying and accumulating in the evaporator in the early stages of defrosting operation, and to eliminate a decrease in the amount of refrigerant circulating, thereby improving defrosting ability, while providing a so-called pump-down operation function that quickly stabilizes the operation. do.

(d) Means for solving the problems The present invention has a compressor, a condenser, an expansion valve, an evaporator, and a heat storage tank, and a hot gas bypass between the discharge side of the compressor and the inlet side of the evaporator. A flow path switching valve is provided at the connection part of the bypass pipe on the compressor side to switch the flow path between the condenser side and the hot gas bypass pipe side. A part of the suction pipe between the compressor and the evaporator is placed in a heat storage tank, and a short-circuit pipe is connected in parallel with the suction pipe to connect the inlet side of the condenser and the outlet side of the evaporator. A refrigerant recovery pipe is provided in between, and a first solenoid valve, a second solenoid valve, a third solenoid valve, and a check valve are provided in each of the short circuit pipe, the refrigerant recovery pipe, and the outlet side pipe of the condenser, and an expansion valve. A refrigeration system in which a fourth solenoid valve is provided in parallel with the refrigeration system, and cooling operation, defrosting operation, and refrigerant recovery operation after defrosting are switched by opening and closing these first to fourth solenoid valves and the flow path switching valve, The flow path switching valve and the solenoid valve are such that during cooling operation, the flow path switching valve is switched to the condenser side, the first solenoid valve and the second solenoid valve are opened, and the third solenoid valve and the fourth solenoid valve are closed. At least in the initial stage of defrosting operation, the flow path switching valve is switched to the hot gas bypass pipe side, the first solenoid valve is closed, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve are opened to recover the refrigerant. During operation, the flow path switching valve is switched back to the condenser side and all electromagnetic valves are closed.

(e) Effect The refrigeration system of the present invention has the above-mentioned equipment configuration. During cooling operation, the heat storage tank is heated with hot gas discharged from the compressor, and during recooling operation after defrosting, the evaporator is heated. The liquefied refrigerant is completely vaporized in the heat storage tank to prevent liquid back-up.
In addition, at the beginning of defrosting operation, the hot gas discharged from the compressor is guided to the evaporator via the hot gas bypass pipe, and in addition to defrosting with hot gas as before, it is also condensed during cooling operation. The high-temperature liquid refrigerant remaining in the container or liquid receiver can be guided into the evaporator via the refrigerant recovery pipe or the condenser outlet pipe due to the pressure difference between the condenser and the evaporator. By heating the evaporator with this high-temperature refrigerant, it is possible to reduce the liquefaction and accumulation of hot gas in the evaporator, suppress the decrease in the amount of refrigerant circulation, and improve the defrosting ability. Furthermore, in the refrigerant recovery operation, after the liquid refrigerant stored in the evaporator during defrosting is vaporized in the heat storage tank,
By making it possible to recover it in the condenser, the refrigeration capacity can be quickly stabilized during recooling operation.

(f) Examples The present invention will be described below based on examples shown in the drawings.

1 is a compressor, 2 is a condenser, 3 is a liquid receiver, 4 is an expansion valve, 5 is an evaporator, and 6 is an accumulator, which are connected in sequence to constitute a refrigeration cycle.

7 is a defrosting device unit, which includes a heat exchange section 9 of a discharge pipe 8 between the compressor 1 and the condenser 2;
and a heat exchange section 11 of a suction pipe 10 between the evaporator 5 and the accumulator 6 are respectively connected for heat exchange. A pressure regulating valve 13 and a short-circuit pipe 1 provided in parallel with the suction pressure regulating valve and the heat exchange section 11.
5, a solenoid valve 14 provided in this short-circuit pipe that is opened only during cooling operation, a three-way switching solenoid valve 16 on the inlet side in parallel with the condenser 2 and receiver 3, and an ejector connection part 17 on the outlet side. A solenoid valve 19 and a check valve 2 are provided in series between the ejector connection portion 17 and the liquid receiver 3.
0, and a refrigerant recovery pipe 22 connecting between the three-way switching solenoid valve 16 and the condenser 2 and the outlet side of the evaporator 5.
and a solenoid valve 21 which is provided in the refrigerant recovery pipe and is opened only during initial defrosting operation. The solenoid valve 19 is open during cooling operation and initial defrosting operation. 23 is a solenoid valve provided in parallel with the expansion valve 4, and this solenoid valve is opened only during defrosting operation.

In the above configuration, during cooling operation, the solenoid valve 1
4 and 19 are open, solenoid valves 21 and 23 are closed, and the three-way switching solenoid valve 16 is open to the condenser 2 side, so the high temperature and high pressure gas refrigerant compressed by the compressor 1 flows as shown by the solid line arrow. Heat storage tank 1 at heat exchange section 9 of discharge pipe 8
The liquid is stored in the liquid receiver 3 through heat exchange with the liquid liquid, and is condensed and liquefied in the condenser 2, and stored in the liquid receiver 3. The liquid receiver 3
The liquid refrigerant stored in Return to and repeat the same process thereafter.

At the beginning of defrosting operation, solenoid valves 19, 21, 23
is open, the solenoid valve 14 is closed, and the three-way switching solenoid valve 16 is open to the hot gas bypass pipe 18 side, so the high temperature discharge gas compressed by the compressor 1 flows through the three-way switching solenoid valve 16 as shown by the dotted arrow. The hot gas flows through the bypass pipe 18, and the high-temperature liquid refrigerant in the condenser 2 and liquid receiver 3 is sucked from the receiver side at the ejector connection part 17 and evaporated via the solenoid valve 23 in a gas-liquid mixed state. At the same time, the high temperature liquid refrigerant in the condenser 2 and receiver 3 is caused to flow from the condenser side through the refrigerant recovery pipe 22 and into the evaporator from the outlet side of the evaporator 5 due to the pressure difference. Let it flow in and store it. After a certain period of time after the liquid refrigerant of the condenser 2 and liquid receiver 3 is supplied into the evaporator 5, the solenoid valves 19 and 21 are closed, and only the hot gas bypass pipe 18 enters a defrosting state. A check valve 20 provided between the ejector connection 17 and the liquid receiver 3 is used to prevent hot gas from entering the liquid receiver 3 when there is a difference between the pressure of the hot gas and the pressure inside the liquid receiver 3. This prevents the refrigerant from flowing backwards and causing a decrease in the amount of refrigerant circulating.

The hot gas that has entered the hot gas defrosting state only in the hot gas bypass pipe 18 defrosts the evaporator 5, undergoes heat exchange, and liquefies the refrigerant into the suction pressure regulating valve 1.
The pressure is reduced in step 3, and the heat exchanger 11 exchanges heat with the heat storage tank 12 to vaporize it, and then it is transferred to the compressor 1 via the accumulator 6.
to return to.

After defrosting, all solenoid valves 14, 19, 21,
23 is closed and the three-way solenoid valve 16 is switched to the condenser 2 side, the liquid refrigerant stored in the evaporator 5 passes through the suction pressure regulating valve 13 and the heat exchange section 11 in the heat storage tank 12 to the compressor 1. The liquid is sucked in, discharged from the compressor, liquefied in the condenser 2, and stored in the receiver 3 because the solenoid valve 19 provided on the outlet side of the receiver is closed. Valves 14 and 19 are opened and cooling operation begins.

In this embodiment, during the initial defrosting operation, after a certain period of time after the high temperature refrigerant is supplied into the evaporator 5,
Although we have described the case where the solenoid valves 19 and 21 are closed and the defrosting operation is started using only the hot gas bypass pipe 18, after the high temperature refrigerant is supplied to the evaporator 5,
The opening and closing states of the solenoid valves 19 and 21 do not affect the defrosting ability thereafter. That is, solenoid valve 1
9 is left open, the flow path switching valve 16 is switched to the hot gas bypass pipe 18 side, and the piping between the solenoid valve 19 and the condenser 2 is provided with a check valve 20. Therefore, the hot gas flowing through the hot gas bypass pipe 18 will not flow back to the outlet side piping of the condenser 2, so the hot gas flowing through the hot gas bypass pipe 18 will not flow back to the outlet side piping of the condenser 2.
The amount of hot gas flowing into the air is the same as when the solenoid valve 19 is closed, and does not significantly affect the defrosting ability. Furthermore, even if the solenoid valve 21 is left open, hot gas will flow into the evaporator 5 via the refrigerant recovery pipe 22 because the flow path switching valve 16 is switched to the hot gas bypass pipe 18 side. This does not happen; the pressures in the condenser 2 and evaporator 5 become equal, and the high-temperature refrigerant in the condenser 2 is no longer supplied to the evaporator 5. Although the liquid treatment after defrosting may be helped by recovering the hot gas little by little to the condenser 2 via the This will not change and will not have a major impact on the defrosting ability.

Furthermore, in this embodiment, the hot gas bypass pipe 18
Although the ejector connection part 17 has been described above, the high temperature refrigerant can be guided to the evaporator 5 due to the pressure difference between the condenser 2 and the evaporator 5 and the suction action by the ejector 17. Depending on the form of the ejector 17, the ejector 17 may not be provided.

Furthermore, since the defrosting device is integrated into a unit, it can be easily incorporated into existing refrigeration equipment.

(G) Effects of the Invention As described above, according to the refrigeration system of the present invention, liquid back-up can be prevented during re-cooling operation after defrosting,
Although it has the conventional function of preventing refrigeration capacity from becoming unstable during recooling operation, at the beginning of defrosting operation, high temperature refrigerant remaining in the condenser is removed from the refrigerant recovery pipe and condenser. The hot gas is supplied to the evaporator through both of the discharge side pipes to heat the evaporator, thereby preventing the hot gas from liquefying and accumulating in the evaporator and reducing the amount of refrigerant circulating due to this, thereby improving the defrosting ability.

[Brief explanation of the drawing]

The figure is a refrigeration circuit diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 4... Expansion valve, 5... Evaporator, 8... Discharge pipe, 9, 11... Heat exchange part, 10...
Suction pipe, 12... Heat storage tank, 13... Suction pressure regulating valve,
14, 19, 21, 22... Solenoid valve, 15... Short circuit pipe, 16... Three-way switching solenoid valve, 17... Ejector connection part, 18... Hot gas bypass pipe, 22... Refrigerant recovery pipe.

Claims (1)

[Claims] 1 Connect the compressor, condenser, expansion valve, and evaporator with piping in sequence, and store each part of the discharge pipe between the compressor and condenser and the suction pipe between the compressor and evaporator inside. The discharge side of the compressor and the inlet side of the evaporator are connected by a hot gas bypass pipe, and the flow path is connected to the connection part of the bypass pipe on the compressor side to connect the condenser side and the hot gas A flow path switching valve is provided to switch between the inlet side of the condenser and the inlet side of the evaporator. A refrigerant recovery pipe having a second solenoid valve is connected to the outlet side, and a third solenoid valve and a check valve are connected in series to the outlet side piping of the condenser, and a fourth solenoid valve is connected in parallel to the expansion valve.
A solenoid valve is provided, and during cooling operation, the flow path switching valve is switched to the condenser side, the first solenoid valve and the third solenoid valve are opened, and the second solenoid valve and the fourth solenoid valve are closed to form a cooling cycle. During defrosting operation, the flow path switching valve is switched to the hot gas bypass pipe side, the first solenoid valve is closed, and the fourth solenoid valve is opened to form a defrosting cycle, and furthermore, during refrigerant recovery operation,
In a refrigeration system in which a refrigerant recovery cycle is formed by switching the flow path switching valve back to the condenser side and closing all solenoid valves, this system includes a second solenoid valve and a second solenoid valve at the beginning of defrosting operation. A refrigeration system characterized by being provided with a mechanism for opening a third solenoid valve.