JP3348465B2 - Binary refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binary refrigeration system commonly referred to as a cascade system multi, and more particularly, to a refrigerant eccentricity generated when a part of a cooling unit in a refrigerator switches from a defrost operation to a cooling operation. The present invention relates to a binary refrigeration apparatus that can prevent the refrigeration.

[0002]

2. Description of the Related Art Cascade connection of a plurality of in-compartment cooling units and one out-of-compartment unit so that heat is exchanged between latent heat of condensation generated in the in-compartment cooling unit and latent heat of evaporation on the outside unit side. Binary refrigeration system called system multi is easy to obtain low temperature,
It is widely used because of its simple structure. The present applicant also discloses a related technique in, for example, JP-A-5-18647.

FIG. 5 shows a main part refrigeration circuit of this type of conventional binary refrigeration system. The device shown in FIG. 5 is provided with two cooling units 2A and 2B, and is cascaded through cascade capacitors 4A and 4B to a chilled unit 1 shown simply as an external unit to cool the inside of the refrigerator to a low temperature. I do. Since the cooling units 2A and 2B have the same structure, only one cooling unit 2A will be described. A well-known refrigeration cycle is formed including the compressor 3A, the high-pressure refrigerant passage of the cascade condenser 4A, the decompressor 5A realized by the expansion valve, and the evaporator 6A. This refrigeration cycle is provided with a hot gas bypass circuit including a defrost solenoid valve 11A. A solenoid valve 9A and an expansion valve 10A realized by a temperature-sensitive expansion valve are connected in series to a low-pressure refrigerant coil 24A that is a cooling system of the cascade condenser 4A. The high-pressure refrigerant liquid is supplied from the chilled unit 1 to the series refrigerant circuit of the solenoid valve 9A, the expansion valve 10A and the low-pressure refrigerant coil 24A, and the latent heat of condensation generated in the cooling unit 2A and the low-pressure refrigerant coil 24A in the cascade condenser 4A. The heat exchanges with the latent heat of evaporation of the low-pressure refrigerant introduced into the evaporator, thereby cooling the inside of the refrigerator in the evaporator 6A.

FIG. 6 shows a flow of a refrigeration operation in the apparatus shown in FIG. Both cooling units 2A, 2B
Are operating individually, and the cooling unit 2A performs the defrost operation and the cooling unit 2B simultaneously performs the cooling operation in step n1. In the cooling unit 2A, since the solenoid valve 9A is closed and the defrost solenoid valve 11A is open, the discharge gas from the compressor 3A bypasses the cascade condenser 4A and the pressure reducer 5A, and the hot gas bypass circuit 8A.
A, and a defrost of a method commonly called a simple hot gas bypass is performed. Since a part of the hot gas also flows into the cascade condenser 4A, the condenser 4A is heated.

[0005] After the defrosting is completed, the process proceeds to step n2.
The process moves to 3, and the operation is switched to the cooling operation. At this point, the temperature-sensitive cylinder 27A of the temperature-sensitive expansion valve 10A is also warmed by heat conduction.

[0006]

At the time when the defrost is completed and the operation is switched to the cooling operation, the defrost solenoid valve 11
Since A is closed and the solenoid valve 9A is opened, a large amount of refrigerant from the chilled unit 1 flows into the cascade condenser 4A of the cooling unit 2A with the solenoid valve 9A being fully opened.
That is, since the temperature-sensitive cylinder 27A is warmed, the refrigerant liquid flows at a stretch because the temperature-sensitive expansion valve 10A is almost fully opened, as in the case where the degree of superheat is large. As a result, the amount of refrigerant supplied from the chilled unit 1 is insufficient on the cooling unit 2B side that continues the cooling operation. As described above, since the refrigerant drift occurs, the cooling unit 2B is overloaded, or the high pressure is abnormally increased, the protection device is activated, and the cooling operation is stopped.

[0007] An object of the present invention is to eliminate abnormal operation by preventing some cooling units from switching to the defrost operation, preventing the refrigerant from drifting easily when the defrost operation is completed and switching to the cooling operation. It is intended to realize stable operation by the operation.

[0008]

SUMMARY OF THE INVENTION The present invention provides a compressor 13,
A refrigeration cycle including a compressor 3n, a cascade condenser 4n, a decompressor 5n, and an evaporator 6n is formed with the external unit 1 in which a series refrigerant circuit including the condenser 14 is provided, and a low pressure, which is a cooling-side path of the cascade condenser 4n. The refrigerant coil 24n is connected to the expansion valve 10n in series,
And a plurality of in-compartment cooling units 2n connected in parallel to the series refrigerant circuit of the out-of-compartment unit 1. Each in-compartment cooling unit 2n is subjected to defrosting of the evaporator 6n by hot gas of its own refrigeration cycle. Refrigeration system provided with hot gas defrost means, wherein each of the in-compartment cooling units 2n includes a low-pressure refrigerant coil 24n.
And a compressor belonging to the in-compartment cooling unit 2n after completion of the defrost operation by the hot gas defrost means so that the degree of superheat at the outlet of the heater becomes constant. Operation switching means for temporarily stopping 3n and then switching to the cooling operation.

Further, according to the present invention, when the compressor 3n belonging to the in-compartment cooling unit 2n is started by operation of the operation switching means, the amount of refrigerant introduced into the corresponding low-pressure refrigerant coil 24n is provided in the in-compartment cooling unit 2n. Characterized in that flow rate limiting means for limiting the pressure is provided.

According to the present invention, in the in-compartment cooling unit 2n, the operation switching means introduces a refrigerant into the corresponding low-pressure refrigerant coil 24n at the same time when the compressor 3n belonging to the in-compartment cooling unit 2n is stopped. The cooling operation is switched after a predetermined time has elapsed or when the outlet temperature of the low-pressure refrigerant coil 24n is stabilized at the set temperature.

[0011]

According to the present invention, each cooling unit 2 in the refrigerator is provided.
n is the low-pressure refrigerant coil 2 of the cascade condenser 4n.
Superheat degree control means for adjusting the degree of opening of the corresponding expansion valve 10n so that the degree of superheat at the 4n outlet is constant is provided. By providing the superheat degree control means for the change in the refrigerating capacity during the cooling operation of each in-compartment cooling unit 2n, it is possible to supply the amount of the refrigerant liquid suitable for the refrigerating capacity from the external unit 1. As a result, stable refrigeration operation without excess or shortage is performed.

On the other hand, an operation switching means for temporarily stopping the compressor 3n when the defrost operation is completed and then switching to the cooling operation is provided. Therefore, at the same time as the completion of the defrost operation, the operation of the in-compartment cooling unit 2n is stopped, the heat intrusion into the cascade condenser 4n can be suppressed, and the temperature can be quickly reduced. Even if the supply is performed, the temperature of the cascade condenser 4n decreases in a very short time, so that the expansion valve 10n
Can be restricted to prevent a large amount of refrigerant from flowing. Cooling unit 2n in the refrigerator after defrost operation is completed
Is switched to the cooling operation when the temperature of the cascade condenser 4n has sufficiently decreased, so that the refrigerant drift is prevented.

Further, according to the present invention, when the compressor 3n is started by switching from the defrost operation to the cooling operation, the amount of refrigerant introduced into the corresponding low-pressure refrigerant coil 24n is limited in the in-compartment cooling unit 2n. Flow control means is provided. Therefore, a large amount of refrigerant flowing into the cascade condenser 4n that enters the cooling operation is forcibly suppressed, and
The refrigerant drift prevention effect is further exhibited. Further, according to the present invention, in the in-compartment cooling unit 2n, the compressor 3n
At the same time as the stop, the refrigerant is introduced into the low-pressure refrigerant coil 24n,
The operation is switched to the cooling operation after the elapse of a predetermined time or when the outlet temperature is stable, so that stable operation can be continued.

[0014]

FIG. 1 is a refrigeration circuit diagram according to a first embodiment of the present invention. The illustrated embodiment includes a chilled unit 1 which is one outdoor unit installed outdoors or in a machine room;
It includes two in-room cooling units 2A and 2B installed inside a freezer or the like. The chilled unit 1 includes a compressor 13, a condenser 14, and an accumulator 17 as main devices.
, A compressor 13 and an accumulator 17 to form a serial refrigerant circuit.
5 and the low-pressure gas line 26 are connected in series. Further, a bypass pipe line having a temperature-sensitive expansion valve 16 is connected in parallel to the series refrigerant circuit.

The compressor 13 is, for example, a scroll compressor, and has a discharge port and an intermediate pressure port inside the cylinder.
The intermediate pressure port and the suction port are connected by a resistance line provided with a capillary tube 19 and a bypass line provided with an unload solenoid valve 18. On the other hand, the discharge port of the compressor 13 and the refrigerant inlet of the accumulator 17 are connected by a pipeline having a constant-pressure expansion valve 15, and the oil outlet of the oil separator 20 and the suction port of the compressor 13 are connected to a capillary tube 21. Connected by an oil return line comprising

The compressor 13 operates at a rated output by closing the unload solenoid valve 18 and operates at a low output by opening the unload solenoid valve 18, depending on the cooling capacity of the in-compartment cooling units 2A and 2B. Output is adjusted. Further, the chilled unit 1 includes a constant pressure expansion valve 15.
, The pressure of the discharge gas line connected to the discharge port of the compressor 13 is controlled to be constant, and the valve opening of the temperature-sensitive expansion valve 16 adjusts the suction on the suction side of the compressor 13. The degree of gas superheat is controlled to be constant.

Since the cooling units 2A and 2B have the same configuration of the refrigeration circuit, the cooling unit 2A will be described below. Items common to the cooling units in the refrigerator may be indicated by adding “n” instead of “A” and “B”. Further, the “cooling unit in the refrigerator” may be simply referred to as “cooling unit”. The cooling unit 2A includes the compressor 3
A, a cascade condenser 4A, a decompressor 5A realized by a temperature-sensitive expansion valve, an evaporator 6A, and an accumulator 7A are provided, and a known refrigeration cycle is constituted by such refrigeration equipment. The cooling unit 2A is further provided with a hot gas bypass circuit 8A. The hot gas bypass circuit 8A is a refrigerant circuit in which a defrost solenoid valve 11A and a drain pan heater 12A provided at a lower portion of the evaporator 6A are connected in series by a pipe, and is parallel to the temperature-sensitive expansion valve 5A. Is provided in connection with.

The cascade condenser 4A includes a compressor 3A
A heat exchanger in which a cooled side path into which the high-temperature and high-pressure refrigerant gas discharged from the chilled unit 1 is introduced and a low-pressure refrigerant coil 24A as a cooling side path through which the low-pressure refrigerant in the chilled unit 1 is introduced are heat-exchangeable. is there. An expansion valve 10A realized by a temperature-sensitive expansion valve and an electromagnetic valve 9A are connected in series to the low-pressure refrigerant coil 24A to form a serial refrigerant circuit.
This series refrigerant circuit is connected to the low-pressure gas line 26 by the high-pressure liquid line 2.
5 is connected in series. Note that an electromagnetic valve 28A is connected in parallel to the expansion valve 10A.

In the cooling unit 2A, when the compressor 3A is driven, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3A exchanges heat with the low-pressure refrigerant guided into the low-pressure refrigerant coil 24A in the cascade condenser 4A. After being condensed and liquefied, the pressure is reduced by the temperature-sensitive expansion valve 5A and becomes a low-pressure low-temperature liquid refrigerant, which is guided to the evaporator 6A. The evaporator 6A evaporates by exchanging heat with the internal air circulated and blown by the evaporator fan 23A, becomes a low-pressure gas refrigerant, and is sucked into the compressor 3A via the accumulator 7A. As described above, the cooling operation for cooling the inside air is performed by performing the circulation accompanied by the condensation and evaporation of the refrigerant. In addition,
During the cooling operation, the solenoid valve 28A is closed.

On the other hand, in the chilled unit 1, when the compressor 13 is driven, the high-temperature and high-pressure gas refrigerant discharged from the compressor 13 is exchanged with the outside air circulated and blown by the condenser fan 22 in the condenser 14. After being exchanged and condensed and liquefied, it passes through the high-pressure liquid line 25, passes through the solenoid valve 9A, is decompressed by the temperature-sensitive expansion valve 10A to become a low-temperature low-pressure liquid refrigerant, and is led to the low-pressure refrigerant coil 24A to be cooled. The refrigerant exchanges heat with the high-temperature high-pressure gas refrigerant on the 2A side and evaporates, becomes a low-pressure gas refrigerant, and is sucked into the compressor 13 via the low-pressure gas line 26 and the accumulator 17. In this way, by performing the circulation accompanied by the condensation and evaporation of the refrigerant, a refrigeration operation is performed in which the latent heat of condensation generated in each of the cooling units 2A and 2B is discharged outside using the refrigerant as a medium. In this case, the temperature-sensitive expansion valve 10A is a temperature-sensitive cylinder 27A provided along a pipe connected to the outlet of the low-pressure refrigerant coil 24A.
The degree of opening of the valve is adjusted by the low-pressure gas refrigerant temperature detected by the controller to control the degree of superheat constant.

FIG. 2 is a flow chart showing a control mode of the operation control means in the first embodiment shown in FIG. In the first embodiment, each cooling unit 2A, 2B
Perform cooling operation and defrost operation individually,
In both cases, the cooling operation is performed, or one of the cooling operations is performed, and the other is the defrost operation. For example, step m
1, a case where the cooling unit 2A is performing a defrost operation and the cooling unit 2B is performing a cooling operation will be described. In the defrost operation, as in the case of the conventional apparatus shown in FIG. 5, the compressor 3A continues to operate, and the solenoid valve 9A, the solenoid valve 11A, and the solenoid valve 2
8A is opened, the evaporator fan 23A is stopped, and defrost is performed by the hot gas bypass with the low-pressure refrigerant coil 24A interposed. At this time, the low-pressure refrigerant coil 24A
, A liquid refrigerant is introduced and serves as an auxiliary heat source for defrost.

Simultaneously with the start of the defrost operation, the state of the defrost is checked by a timer or a defrost detector. In Step m2, when the completion of the defrost is detected, the flow proceeds to the next Step m3, in which the defrost operation is stopped, and the low-pressure refrigerant flows through the low-pressure refrigerant coil 24A.
That is, the compressor 3A is stopped, the solenoid valve 9A is kept open, the solenoid valve 28A is closed, and the defrost solenoid valve 11A is closed. Note that the evaporator fan 23A is kept stopped. Since the temperature of the pipe in which the temperature-sensitive cylinder 27A is provided has increased by the time defrost is completed, the temperature-sensitive expansion valve 10A is open. Therefore, the low-pressure refrigerant reduced in pressure by the expansion valve 10A is supplied to the cascade condenser 4A. Flows into.

Simultaneously with the completion of defrosting, for example, a timer is operated to count time, and when it is detected in step m4 that several minutes of the set time have elapsed, the flow proceeds to step m5 to switch to the cooling operation. This cooling operation is performed by the compressor 3
A is driven by driving the evaporator fan 23A with the solenoid valve 9A open and the defrost solenoid valve 11A closed.

At the time when the process proceeds to step m3, the cooling unit 2A is switched to the cooling operation in step m5 because the compressor 3A is stopped and the operation is stopped.
Due to the low-pressure refrigerant flowing into the low-pressure refrigerant coil 24A of the cascade condenser 4A, the temperature of the pipe at the outlet of the coil 24A immediately decreases. Therefore, the temperature-sensitive expansion valve 10A is throttled. There is no problem such as inflow, and stable cooling operation is performed.

In FIG. 2, the switching from the completion of defrosting to the cooling operation employs a timer system for detecting a predetermined number of minutes. However, the present invention also includes a low-pressure refrigerant coil 24A outlet. Of course, a gas pipe temperature detection method of starting the cooling operation by detecting the temperature of the gas pipe connected to the apparatus and lowering the temperature to the set temperature may be employed.

FIG. 3 schematically shows the structure of a main part of an in-compartment cooling unit 2n of a refrigeration / refrigeration apparatus according to a second embodiment of the present invention. The second embodiment is similar to the first embodiment, and has the same basic configuration. It should be particularly noted that the expansion valve 10n connected in series to the low-pressure refrigerant coil 24n has a temperature-sensitive function. Electric expansion valve 10n instead of expansion valve
1 is used. In the case of the electric expansion valve 10n1, since the fully-closed and the valve opening degree can be easily and reliably adjusted, the valve opening degree is electrically controlled by a command from the control circuit during the cooling operation. It is possible to perform accurate superheat control. In this embodiment, during the defrost operation, the electric expansion valve 10n1 is fully opened to control the liquid refrigerant to the low-pressure refrigerant coil 24n so that the liquid refrigerant can be used as an auxiliary heat source for defrost. Then, during the cooling operation after the completion of the defrost, the electric expansion valve 10n1 is opened to, for example, a 20% opening degree for only a short time of, for example, about 3 minutes so that an excessive refrigerant does not flow through the low-pressure refrigerant coil 24n. Control is performed such that the temperature of the cascade capacitor 4n is immediately reduced. In the cooling operation after the elapse of 3 minutes, the electric expansion valve 10n is operated in the same manner as before.
The superheat control is performed by 1.

As shown in FIG. 3, thermistors 28n and 29n are added to the refrigerant pipes connected to the inlet and the outlet of the low-pressure refrigerant coil 24n to detect the temperature of each of the pipes. By controlling the valve opening of the electric expansion valve 10n1 so that the temperature of the electric expansion valve 10n1 becomes, for example, 5 ° C., it is possible to accurately control the degree of superheat constant.

FIG. 4 schematically shows a structure of a main part of an in-compartment cooling unit 2n of a refrigeration / refrigeration apparatus according to a third embodiment of the present invention. The third embodiment has the same basic refrigerant circuit configuration for defrosting as the conventional one shown in FIG. It should be noted that an electromagnetic valve 30n is interposed between a temperature-sensitive expansion valve 10n and an electromagnetic valve 9n connected in series to the inlet side of the low-pressure refrigerant coil 24n.
This is a point that a refrigerant circuit is formed in which a capillary tube 31n is connected in parallel to a series refrigerant circuit of 0n and a solenoid valve 30n. In the third embodiment, during the defrost operation, the solenoid valve 9n is closed to stop the refrigerant from flowing into the low-pressure refrigerant coil 24n, and defrost is performed by a simple hot gas bypass. Simultaneously with the completion of the defrost, the solenoid valve 9n is opened and the solenoid valve 30n is closed. By this valve opening / closing operation, an appropriate amount of low-pressure refrigerant decompressed by the capillary tube 31n flows into the low-pressure refrigerant coil 24n, and the cascade condenser 4n
It is possible to quickly lower the temperature of n and prevent the refrigerant from drifting. After the solenoid valve 30n is closed by a timer, for example, for 3 minutes, the cooling unit 2n
To be opened in response to the start of the cooling operation. As a result, the superheat degree control mainly using the temperature-sensitive expansion valve 10n is performed. Also in this embodiment, it is possible to surely prevent the refrigerant drift which tends to occur at the time of switching from the defrost operation to the cooling operation.

In the first and second embodiments described above,
Hot gas defrost using the liquid refrigerant from the chilled unit 1 as an auxiliary heat source. In the third embodiment, simple hot gas defrost is performed, but any type of defrost may be performed.

[0030]

As described above, according to the present invention, in the refrigeration / refrigeration system of the cascade connection type, that is, in the binary refrigeration system, of the cooling units 2n in the refrigerator, the one performing the defrost operation is determined by the completion of the defrost operation. When switching to the cooling operation, the temperature of the cascade condenser 4n of the in-compartment cooling unit 2n is quickly lowered by temporarily stopping the corresponding compressor 3n and then starting the cooling operation so that the cooling operation is started when the cooling operation is started. Can be prevented from flowing in a large amount, so that the cooling unit 2n in the refrigerator can be prevented from stopping due to overload or abnormally high pressure, and stable operation can be continued.

[Brief description of the drawings]

FIG. 1 is a refrigeration circuit diagram according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a control mode of operation control means in the first embodiment shown in FIG. 1;

FIG. 3 is a refrigeration circuit diagram schematically showing a main part structure of a cooling unit 2n in a refrigerator according to a second embodiment of the present invention.

FIG. 4 is a refrigeration circuit diagram schematically illustrating a main part structure of an in-compartment cooling unit 2n according to a third embodiment of the present invention.

FIG. 5 is a refrigeration circuit diagram of a conventional binary refrigeration apparatus.

6 is a flow chart of a refrigeration operation of the apparatus shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chilled unit 2A, B, n Cooling unit 3A, B13 Compressor 4A, B, n Cascade condenser 5A, B Decompressor 6A, B Evaporator 8A, B Hot gas bypass circuit 9A, B, n Solenoid valve 10A , B, n expansion valve 10n1 electric expansion valve 11A, B, n defrost solenoid valve 14 condenser 24A, B, n low pressure refrigerant coil 28A, B solenoid valve

Continuation of the front page (56) References JP-A-2-192559 (JP, A) JP-A-5-18647 (JP, A) JP-A-5-36258 (JP, U) (58) Fields surveyed (Int) .Cl. ⁷ , DB name) F25B 47/02 540 F25B 7/00

Claims (3)

(57) [Claims] 1. A refrigerating cycle including an external unit 1 provided with a series refrigerant circuit including a compressor 13 and a condenser 14, a compressor 3n, a cascade condenser 4n, a decompressor 5n, and an evaporator 6n is formed. The low-pressure refrigerant coil 24n, which is the cooling-side path of the condenser 4n,
n are connected in parallel to the serial refrigerant circuit of the external unit 1 via the respective n in series.
n is a binary refrigeration apparatus provided with hot gas defrost means for performing defrosting of the evaporator 6n by hot gas of its own refrigeration cycle. The internal cooling unit 2n includes a superheat control unit that adjusts the opening of the corresponding expansion valve 10n so that the superheat at the outlet of the low-pressure refrigerant coil 24n is constant, and after completion of the defrost operation by the hot gas defrost unit. , The compressor 3n belonging to the in-compartment cooling unit 2n
Operation switching means for temporarily stopping the operation and then switching to the cooling operation. 2. The in-compartment cooling unit 2n includes:
The flow rate limiting means for limiting the amount of refrigerant introduced into the corresponding low-pressure refrigerant coil 24n when the compressor 3n belonging to the in-compartment cooling unit 2n is started by the operation of the operation switching means, is provided. A binary refrigeration device as described. 3. The in-compartment cooling unit 2n
The operation switching means introduces the refrigerant into the corresponding low-pressure refrigerant coil 24n at the same time when the compressor 3n belonging to the in-compartment cooling unit 2n is stopped, and a predetermined time has elapsed, or the outlet temperature of the low-pressure refrigerant coil 24n has reached the set temperature 2. The binary refrigeration system according to claim 1, wherein the cooling operation is switched to the cooling operation by stabilization.