JP2002277082A - Freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control refrigeration facility in accordance with an increase in the load of a refrigerating chamber without remarkably reducing the temperature thereof in the case where the load of the freezing chamber alone increases when the ambient temperature is low and the load is small in a two-stage refrigerant compressor type freezer having a plurality of evaporators different in evaporating temperature as typified by a freezer-refrigerator and the like. SOLUTION: It is possible to meet a change in load balance between freezing and refrigerating chambers by reducing heat quantity exchanged between the refrigerating chamber and a refrigerating evaporator 3 to lower the evaporating temperature thereof, increasing the intensity of supercooling a liquid refrigerant supplied to a freezing evaporator 1 and thereafter increasing the operating rate or revolution speed of a compressor 5 to adjust the circulation of the refrigerant in accordance with the load of the freezing chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the capacity of a refrigerant two-stage compression refrigeration system having a plurality of evaporators having different evaporation temperatures, such as a refrigerator-freezer.

[0002]

2. Description of the Related Art At present, energy saving of refrigerating apparatuses such as refrigerators and refrigerators has been promoted from the viewpoint of prevention of global warming.
Conventionally, in refrigerators that cool at different temperatures, such as a freezer compartment and a refrigerator compartment, a single evaporator is cooled to a temperature lower than the freezer compartment temperature to exchange heat with the air in the refrigerator, and the temperature in the refrigerator is adjusted by the amount of heat exchange. Was controlled by. On the other hand, by operating the two evaporators at the freezing room temperature and the cold room temperature independently of the freezing room and the cold room evaporator, the cooling room cooling cycle with a relatively low compression ratio and high theoretical efficiency is achieved. Attempts have been made to achieve energy savings by utilizing the technology.

[0003] Specifically, two cycles in which the freezer compartment cooling cycle and the refrigerator compartment cooling cycle are completely independent, and switching in which the compressor and the condenser are shared and the evaporator is switched to alternately cool the freezer compartment and the refrigerator compartment. And a two-stage compression cycle in which the refrigerating room evaporator is used as an intercooler and the return gas refrigerant from the freezing room evaporator is compressed in two stages. Among them, the two-stage compression cycle has attracted attention as a method for maximizing the use of a refrigerator room cooling cycle having high theoretical efficiency.

[0004] For example, Japanese Patent Application Laid-Open Nos. 5-223368 and 5-223370 disclose a refrigerator-freezer using a two-stage compression cycle. Hereinafter, features of a conventional refrigeration system using a two-stage compression cycle will be described with reference to the drawings.

FIG. 4 shows a cycle configuration of a conventional refrigeration system. In FIG. 4, 1 is a freezing evaporator, 2 is a freezing fan for promoting heat exchange between the air in the freezing room (not shown) and the freezing evaporator 1, 3 is a refrigerating evaporator, and 4 is a refrigerating room. A refrigeration fan for promoting heat exchange between the air inside (not shown) and the refrigeration evaporator 3, 5 is a compressor, 6 is a low-stage compression element of the compressor 5, and 7 is a high-stage side of the compressor 5. Compression element, 8 is a condenser, 9
Is a refrigeration expansion mechanism, 10 is a refrigeration expansion mechanism, and 11 is a heat transfer mechanism for exchanging heat between the liquid refrigerant supplied to the refrigeration expansion mechanism 9 and the refrigeration evaporator 3.

Generally, the temperature of the freezer evaporator 1 is about -30 ° C. and the temperature of the refrigerating evaporator 3 is about -30 ° C. It is controlled to about -10 ° C. Therefore, the pressure of the return gas refrigerant evaporated in the refrigerating evaporator 1 is lower than the pressure of the return gas refrigerant evaporated in the refrigerating evaporator 3, and is compressed by the low-stage compression element 6 of the compressor 5 until the same pressure is reached. You.

[0007] The discharge gas refrigerant of the low-stage compression element 6 of the compressor 5 and the return gas refrigerant evaporated in the refrigeration evaporator 3 are mixed, and the high-stage compression element 7 of the compressor 5 mixes the condenser 8. Compressed to a pressure of Generally, since the condenser 8 is air-cooled in the air, the refrigerant condenses at an outside air temperature of about +10 to 20 ° C.

The liquid refrigerant condensed in the condenser 8 is distributed to the freezing expansion mechanism 9 and the refrigerating expansion mechanism 10, and supplied to the freezing evaporator 1 and the refrigerating evaporator 3, respectively. At this time, the liquid refrigerant sent to the refrigeration expansion mechanism 9 exchanges heat with the refrigeration evaporator 3 via the heat transfer mechanism 11 to change the temperature from a temperature close to the condenser 8 to a temperature close to the refrigeration evaporator 3. Supercooled. As a result, the refrigeration effect of the liquid refrigerant supplied to the refrigeration evaporator 1 increases, so that the refrigerant circulation amount of the refrigeration evaporator 1 can be suppressed.

As described above, in the two-stage compression cycle in which the refrigerating evaporator 3 is used as an intercooler and the return gas refrigerant from the refrigerating evaporator 1 is compressed in two stages, the refrigerant circulation amount of the low-stage compression element 6 is increased. On the other hand, the amount of refrigerant circulating through the high-stage compression element 7 having a high theoretical efficiency can be increased to a value equal to or higher than the capacity ratio of the refrigerating compartment to the freezing compartment, thereby saving energy.

[0010]

However, in the above-mentioned conventional configuration, when only the load on the freezing compartment increases when the outside air temperature is low and the load is small, the rotational speed of the compressor is reduced in order to suppress the rise in the temperature of the freezing compartment. When the refrigerant circulation amount of the refrigerating evaporator is increased, the refrigerant circulation amount of the refrigerating evaporator is also increased at the same time, and the refrigerating room temperature may be significantly reduced.

Therefore, in a two-stage compression cycle in which the refrigerating room evaporator is used as an intercooler to compress the return gas refrigerant from the freezing room evaporator in two stages, the ability to cope with a change in the load balance of the freezing room with respect to the refrigerating room. Control specifications are desired.

According to the present invention, by controlling the cooling control mechanism of the freezer compartment and the capacity of the refrigerating fan, a refrigerating capacity control capable of coping with a change in the load balance of the freezer compartment with respect to the refrigerator compartment is achieved.

[0013]

SUMMARY OF THE INVENTION Accordingly, the refrigerating apparatus of the present invention reduces the amount of heat exchange between the refrigerating compartment and the refrigerating evaporator when the load on the refrigerating compartment suddenly increases, thereby reducing the evaporation temperature of the refrigerating evaporator. The method uses a capacity control method for lowering and increasing the amount of subcooling of the liquid refrigerant supplied to the refrigeration evaporator.

According to the present invention, when only the load on the freezing compartment increases when the outside air temperature is low and the load is small, the amount of refrigerant circulating from the refrigerating evaporator to the refrigerating evaporator is reduced without lowering the temperature of the refrigerating compartment. Then, by increasing the operation rate or the number of revolutions of the compressor to adjust the circulation amount of the refrigerant according to the load of the freezing room, it is possible to cope with a change in the load balance of the freezing room with respect to the refrigerator room as a result. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a refrigerating evaporator for cooling a freezing room, a refrigerating evaporator for cooling a freezing room, and a return gas refrigerant from the refrigerating evaporator. , A high-stage compression mechanism that compresses a mixture of the return gas refrigerant from the refrigeration evaporator and the discharge gas refrigerant of the low-stage compression mechanism, and condenses the discharge gas refrigerant of the high-stage compression mechanism. A condenser, a refrigeration expansion mechanism for reducing the pressure of the liquid refrigerant condensed by the condenser and supplying the refrigerant to the refrigeration evaporator, and a supercooling temperature for cooling the liquid refrigerant supplied to the refrigeration evaporator with the refrigeration evaporator. And a refrigeration apparatus having a refrigeration expansion mechanism for reducing the pressure of the liquid refrigerant condensed by the condenser and supplying the refrigeration to the evaporator for refrigeration. Evaporation temperature of refrigeration evaporator by reducing heat exchange amount of refrigeration evaporator And a control method for increasing the subcooling amount of the liquid refrigerant supplied to the refrigeration evaporator. The refrigerant circulation amount of the refrigeration evaporator with respect to the refrigeration evaporator can be reduced without lowering the temperature, and then the operating rate or the number of revolutions of the compressor is increased to adjust the refrigerant circulation amount according to the load of the freezing compartment. This has the effect of responding to a change in the load balance of the freezer compartment with respect to the refrigerator compartment as a result.

Here, when HFC134a is used as the refrigerant in a system in which the freezing capacity of the freezing compartment is substantially equal to that of the freezing compartment, the temperature of the refrigeration evaporator is changed from -10 ° C to -15 ° C.
, The density of the gas refrigerant sucked into the high-stage compression mechanism is reduced from about 8.4 kg / m ³ to about 6.8 kg / m ³ .
Since the amount of gas refrigerant discharged from the low-stage compression mechanism hardly changes, the amount of refrigerant circulating in the refrigeration evaporator can be reduced by about 38%. Also, the temperature of the refrigerant flowing into the freezing evaporator using the refrigeration evaporator is set to the temperature of the condenser, for example, 30 ° C.
By supercooling the temperature of the refrigeration evaporator to −15 ° C., the refrigeration capacity of the refrigeration evaporator is increased by about 33% and the refrigeration capacity of the refrigeration evaporator is reduced by about 33%.
As a result, the freezing capacity ratio of the freezer compartment to the refrigerator compartment is 10
It can be increased from 0/100 to 133/29. Thereafter, by increasing the operation rate or the number of revolutions of the compressor to increase the amount of circulating refrigerant, the refrigerating capacity ratio is set to 133 / maximum within a range where the refrigerating capacity of the refrigerating compartment does not become excessive.
The freezing capacity of the freezing room can be increased to 29 to 459/100.

At this time, if the temperature of the refrigerating evaporator is further lowered, the capacity of the refrigerating evaporator can be further lowered. However, if the compression ratio of the low-stage compression mechanism is lowered, the actual efficiency is lowered. Up to a degree is desirable. Further, in this calculation, the refrigerant flowing into the refrigeration evaporator is not supercooled during the normal operation. However, if there is enough capacity control width corresponding to the change in the load balance, the room temperature to the refrigeration evaporator (-
Performing supercooling at 10 ° C.) can increase the efficiency during normal operation. However, the supercooling temperature during normal operation is -1
When performed at 0 ° C., the capacity change when supercooling to −15 ° C. becomes about 4%, and as a result, the control range of the freezing capacity of the freezer to the freezer within a range where the freezing capacity of the freezer does not become excessive is 104/58 to 179/100.

According to a second aspect of the present invention, there is provided a refrigerating evaporator for cooling a freezing room, a refrigerating evaporator for cooling a refrigerating room, and a low-pressure evaporator for compressing a return gas refrigerant from the refrigerating evaporator. A stage compression mechanism, a high stage compression mechanism that compresses a mixture of the return gas refrigerant from the refrigerating evaporator and the discharge gas refrigerant of the low stage compression mechanism, and a condenser that condenses the discharge gas refrigerant of the high stage compression mechanism, A refrigeration expansion mechanism that decompresses the liquid refrigerant condensed by the condenser and supplies it to the refrigeration evaporator; A separator, a refrigeration expansion mechanism for decompressing the liquid refrigerant separated by the gas-liquid separator and supplying the refrigerant to the refrigeration evaporator, and a second refrigerant for decompressing the liquid refrigerant condensed by the condenser and supplying the refrigerant to the refrigeration evaporator. In a refrigeration system having a refrigeration expansion mechanism, when the load of the A control method that reduces the amount of heat exchange between the storage chamber and the refrigeration evaporator to lower the evaporation temperature of the refrigeration evaporator, and reduces the amount of liquid refrigerant passing through the second refrigeration expansion mechanism, If only the load of the freezing compartment increases when the outside temperature is low and the load is small, the amount of refrigerant circulating from the refrigerating evaporator to the refrigerating evaporator can be reduced without lowering the temperature of the refrigerating compartment, and then the compressor is operated. By increasing the rate or the number of revolutions and adjusting the refrigerant circulation amount according to the load of the freezing room, as a result, it has an action corresponding to a change in the load balance of the freezing room with respect to the refrigerator room,
By adjusting the refrigerant flow ratio between the refrigeration expansion mechanism and the second refrigeration expansion mechanism, the supercooling amount of the liquid refrigerant supplied to the refrigeration evaporator is arbitrarily controlled to improve the efficiency during normal operation. Has an action.

Here, the liquid refrigerant supplied from the gas-liquid separator to the refrigerating evaporator after passing through the refrigerating expansion mechanism is supercooled to the temperature of the refrigerating evaporator in the refrigerating evaporator. The operation and effect when switching between the refrigerating expansion mechanism and the second refrigerating expansion mechanism are the same as those of the first aspect of the present invention. Further, by adjusting the refrigerant flow ratio between the refrigeration expansion mechanism and the second refrigeration expansion mechanism, the amount of subcooling of the liquid refrigerant supplied to the refrigeration evaporator can be arbitrarily controlled. The efficiency of the refrigeration cycle can be improved by increasing the refrigerant flow rate of the high-stage compression mechanism having a low compression ratio and a high theoretical efficiency by the amount of the compression.

When the liquid refrigerant supplied to the refrigerating evaporator is supercooled by using the gas-liquid separator, the liquid refrigerant in the gas-liquid separator is removed when the load in the refrigerator compartment becomes excessive as in the case of pull-down. Temporarily depleted. At this time, by mainly using the second freezing expansion mechanism, the refrigerating compartment and the freezing compartment can be cooled in a well-balanced manner.

According to a third aspect of the present invention, in the first or second aspect, a low-stage compressor comprising a low-stage compression mechanism and a low-stage variable speed motor; Mechanism and a high-stage compressor consisting of a high-speed variable speed motor.If only the load in the freezer compartment increases when the outside air temperature is low and the load is small, the evaporation for refrigeration can be performed without lowering the temperature in the refrigerator compartment. The amount of circulating refrigerant in the refrigeration evaporator with respect to the refrigerator can be reduced, and then the operating rate or the number of revolutions of the compressor is increased to adjust the amount of circulating refrigerant in accordance with the load in the freezing room. In addition to having an action corresponding to a change in the load balance of the chamber, it has an action of increasing the rotation speed of the low-stage compression mechanism with respect to the high-stage compression mechanism and increasing the refrigerating capacity of the freezing chamber with respect to the refrigerator compartment.

Here, when the freezing control width of the freezing compartment with respect to the refrigerating compartment is small, the rotation speed of the low-stage compression mechanism is increased, and the rotation of the high-stage compression mechanism is increased by the increment of the discharge gas refrigerant amount of the low-stage compression mechanism. By increasing the number and increasing the refrigerating capacity of the freezing compartment relative to the refrigerating compartment, the capacity can be controlled without lowering the temperature of the refrigerating evaporator.

When only the load in the refrigerator compartment increases when the outside air temperature is low and the load is small, usually, when the temperature of the refrigerating evaporator is lowered, the density of the gas refrigerant sucked by the low-stage compression mechanism decreases and the gas refrigerant is discharged. The amount of gas refrigerant decreases, and the amount of return gas refrigerant from the refrigeration evaporator that the high-stage compression mechanism draws in increases, thereby increasing the refrigeration capacity of the refrigeration evaporator. When the temperature of the evaporator decreases, the compression ratio of the low-stage compression mechanism increases and the theoretical efficiency decreases. Similarly, in this case, if the refrigerating capacity of the refrigerating compartment with respect to the freezing compartment is increased by increasing the rotation speed of the high-stage compression mechanism relative to the low-stage compression mechanism, the capacity adjustment can be performed without lowering the theoretical efficiency.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. The same components as those in the related art are denoted by the same reference numerals, and detailed description is omitted.

(Embodiment 1) The cycle configuration and operation of the refrigeration system of Embodiment 1 will be described with reference to FIG. Figure 1
, 1 is a freezing evaporator, 2 is a freezing room (not shown)
A refrigeration fan for promoting heat exchange between the air inside and the refrigeration evaporator 1, a refrigeration evaporator 3, and a refrigeration evaporator 3 for heat exchange between the air in the refrigeration room (not shown) and the refrigeration evaporator 3. Refrigeration fan, 5 is a compressor, 6 is a low-stage compression element of the compressor 5, 7
Is a high-stage compression element of the compressor 5, 8 is a condenser, 9 is a refrigerating expansion mechanism, 10 is a refrigerating expansion mechanism, and 11 is a liquid refrigerant supplied to the refrigerating expansion mechanism 9 and a refrigerating evaporator 3. A heat transfer mechanism 12 for exchanging heat is a switching valve for switching a flow path of the liquid refrigerant supplied to the refrigeration evaporator 1 via the refrigeration expansion mechanism 9.

In general, the temperature of the freezing evaporator 1 is about -30 ° C. and the temperature of the refrigerating evaporator 3 is about -30 ° C. It is controlled to about -10 ° C. In addition, since the condenser 8 is air-cooled in the atmosphere, the refrigerant condenses at an outside air temperature of about +10 to 20 ° C.

During normal operation, the liquid refrigerant condensed in the condenser 8 is distributed to the refrigeration expansion mechanism 9 and the refrigeration expansion mechanism 10 and supplied to the refrigeration evaporator 1 and the refrigeration evaporator 3, respectively. . At this time, the liquid refrigerant sent to the refrigeration expansion mechanism 9 is directly supplied from the switching valve 12 to the refrigeration expansion mechanism 9 without passing through the heat transfer mechanism 11.

When the load on the freezer compartment suddenly increases, the number of heat exchanges between the refrigerating compartment and the refrigerating evaporator 3 is reduced by lowering the rotation speed of the refrigerating fan 4 and the evaporating temperature of the refrigerating evaporator 3 is reduced. Is lowered from -10 ° C. to about −15 ° C., and the switching valve 12 is operated so that the liquid refrigerant condensed in the condenser 8 is sent to the refrigeration expansion mechanism 9 via the heat transfer mechanism 11. At this time, the liquid refrigerant sent to the refrigeration expansion mechanism 9 is supercooled from a temperature close to the condenser 8 to a temperature close to the refrigeration evaporator 3. As a result, the amount of refrigerant supplied to the refrigeration evaporator 3 is reduced, the refrigeration capacity of the refrigeration evaporator 3 is reduced by the heat load of the heat transfer mechanism 11, and at the same time, the refrigeration capacity of the refrigeration evaporator 1 is reduced. The refrigerating capacity of the freezing room with respect to the refrigerating room is improved. Thereafter, the operating rate or the number of revolutions of the compressor 5 is increased to adjust the refrigerant circulation amount in accordance with the load of the freezing room, thereby making it possible to cope with a change in the load variation of the freezing room with respect to the refrigerator room.

In this embodiment, the liquid refrigerant sent to the refrigeration expansion mechanism 9 is supercooled from the temperature near the condenser 8 to the temperature near the refrigeration evaporator 3 by using the heat transfer mechanism 11. Similar characteristics can be expected even if the subcooling amount is adjusted according to the heat load of the room.

(Embodiment 2) The cycle configuration and operation of a refrigeration apparatus according to Embodiment 2 will be described with reference to FIG. FIG.
, 1 is a freezing evaporator, 2 is a freezing room (not shown)
A refrigeration fan for promoting heat exchange between the air inside and the refrigeration evaporator 1, a refrigeration evaporator 3, and a refrigeration evaporator 3 for heat exchange between the air in the refrigeration room (not shown) and the refrigeration evaporator 3. Refrigeration fan, 5 is a compressor, 6 is a low-stage compression element of the compressor 5, 7
Is a high-stage compression element of the compressor 5, 8 condensers, 9 is a refrigeration expansion mechanism, 10 is a refrigeration expansion mechanism, and 11 is a liquid refrigerant supplied to the refrigeration expansion mechanism 9 and heats the refrigeration evaporator 3. A heat transfer mechanism for exchange, 13 is a gas-liquid separator for separating the refrigerant at the outlet of the refrigeration evaporator 3 into gas and liquid, and supplying the gas phase to the high-stage compression element 5 and the liquid phase to the refrigeration evaporator 1; This is a second refrigeration expansion valve for reducing the pressure of the liquid refrigerant separated by the gas-liquid separator 13 and supplying it to the refrigeration evaporator 1.

Generally, the temperature of the freezer evaporator 1 is about -30 ° C., and the temperature of the refrigerating evaporator 3 is about -30 ° C. It is controlled to about -10 ° C. In addition, since the condenser 8 is air-cooled in the atmosphere, the refrigerant condenses at an outside air temperature of about +10 to 20 ° C.

During normal operation, the liquid refrigerant condensed in the condenser 8 is distributed to the refrigeration expansion mechanism 9 and the refrigeration expansion mechanism 10 and supplied to the refrigeration evaporator 1 and the refrigeration evaporator 3, respectively. . At this time, the refrigeration expansion mechanism 9 and the second refrigeration expansion mechanism 14 are in a half-open state, and the amounts of the refrigerant passing therethrough are adjusted to be equal. Further, the refrigerating capacity of the refrigerating evaporator 3 is adjusted by using the rotation speed of the compressor 5 and the refrigerating expansion mechanism 10 so that the liquid refrigerant staying in the gas-liquid separator 13 does not overflow. As a result, the liquid refrigerant supercooled to the evaporation temperature of the refrigeration evaporator 3 −10 ° C. is supplied to the refrigeration evaporator 1 via the second refrigeration expansion mechanism 14, and thus is supplied via the refrigeration expansion mechanism 9. As a result, the temperature of the liquid refrigerant supplied to the refrigeration evaporator 1 is reduced, and the cycle efficiency can be improved during normal operation.

When the load on the freezer compartment suddenly increases, the number of heat exchanges between the refrigerating compartment and the refrigerating evaporator 3 is reduced by lowering the rotation speed of the refrigerating fan 4 and the evaporating temperature of the refrigerating evaporator 3 is reduced. Is lowered from -10 ° C. to about −15 ° C., and only the liquid refrigerant separated by the gas-liquid separator 13 by fully closing the refrigeration expansion mechanism 9 and fully opening the second refrigeration expansion mechanism 14 is subjected to the second refrigeration expansion. It is sent to the refrigerating evaporator 1 via the mechanism 14. At this time, the liquid refrigerant sent to the second expansion mechanism for freezing 14 is supercooled in the evaporator 3 from a temperature close to the condenser 8 to a temperature close to the evaporator 3. As a result,
The amount of the refrigerant supplied to the refrigeration evaporator 3 is reduced, and the refrigeration is performed by an increase in the heat load of the liquid refrigerant sent from the gas-liquid separator 13 to the refrigeration evaporator 1 via the second refrigeration expansion mechanism 14. The refrigerating capacity of the refrigerating evaporator 3 is reduced, and at the same time, the refrigerating capacity of the refrigerating evaporator 1 is increased, and the refrigerating capacity of the refrigerating compartment with respect to the refrigerating compartment is improved. Thereafter, the operating rate or the number of revolutions of the compressor 5 is increased to adjust the circulation amount of the refrigerant in accordance with the load of the freezing compartment, thereby making it possible to cope with a change in the load balance of the freezing compartment with respect to the refrigerator compartment.

In this embodiment, the amount of the refrigerant passing through the refrigeration expansion mechanism 9 and the second refrigeration expansion mechanism 14 during normal operation is adjusted so as to be equal, but the heat load of the freezing compartment is reduced. Similar characteristics can be expected even if the refrigerant distribution amount is adjusted accordingly. When the refrigeration capacity of the refrigeration evaporator 3 is insufficient and the liquid refrigerant in the gas-liquid separator 13 is depleted, as in the case of pull-down, the refrigeration expansion mechanism 9 is fully opened and the second refrigeration expansion mechanism 14 is turned off. If the liquid refrigerant to be supplied to the refrigerating evaporator 1 is fully closed to secure the liquid refrigerant, the refrigerating compartment and the refrigerating compartment can be cooled in a well-balanced manner.

(Embodiment 3) The cycle configuration and operation of a refrigeration apparatus according to Embodiment 3 will be described with reference to FIG. FIG.
, 1 is a freezing evaporator, 2 is a freezing room (not shown)
A refrigeration fan for promoting heat exchange between the air inside and the refrigeration evaporator 1, a refrigeration evaporator 3, and a refrigeration evaporator 3 for heat exchange between the air in the refrigeration room (not shown) and the refrigeration evaporator 3. Refrigeration fan, 15 is a low stage compressor, 16 is a low stage compression mechanism of the low stage compressor 15, 17 is a low stage motor for driving the low stage compression mechanism 16 of the low stage compressor 15, 18 is a high stage compressor , 19 is a high-stage compression mechanism of the high-stage compressor 18, 20 is a high-stage motor for driving the high-stage compression mechanism 19 of the high-stage compressor 18, 8 is a condenser, 9 is a freezing expansion mechanism, and 10 is a refrigerator. An expansion mechanism, 11 is a heat transfer mechanism for exchanging heat between the liquid refrigerant supplied to the refrigeration expansion mechanism 9 and the refrigeration evaporator 3, and 12 is a liquid supplied to the refrigeration evaporator 1 via the refrigeration expansion mechanism 9. This is a switching valve that switches the flow path of the refrigerant. The low-stage compression mechanism 16 compresses the return gas refrigerant of the refrigeration evaporator 1, compresses the mixed gas refrigerant of the discharge gas refrigerant and the return gas refrigerant of the refrigeration evaporator 3 by the high-stage compression mechanism 19, 8 At this time, the low-stage motor 17 and the high-stage motor 20 are controlled independently.

Generally, the temperature of the freezing evaporator 1 is about -30 ° C. and the temperature of the refrigerating evaporator 3 is about -30 ° C. It is controlled to about -10 ° C. In addition, since the condenser 8 is air-cooled in the atmosphere, the refrigerant condenses at an outside air temperature of about +10 to 20 ° C.

During normal operation, the liquid refrigerant condensed in the condenser 8 is distributed to the refrigeration expansion mechanism 9 and the refrigeration expansion mechanism 10, and supplied to the refrigeration evaporator 1 and the refrigeration evaporator 3, respectively. . At this time, the liquid refrigerant sent to the refrigeration expansion mechanism 9 is directly supplied from the switching valve 12 to the refrigeration expansion mechanism 9 without passing through the heat transfer mechanism 11. At this time, the low-stage motor 17 and the high-stage motor 20 are independently controlled, and the low-stage compression mechanism 16 and the high-stage compression mechanism 16 are rotated at a rotational speed commensurate with the refrigerant supply amounts of the refrigerating evaporator 1 and the refrigerating evaporator 3. Step compression mechanism 19
Drive.

When the load on the freezing compartment suddenly increases, the number of heat exchange between the refrigerating compartment and the refrigerating evaporator 3 is reduced by lowering the rotation speed of the refrigerating fan 4 and the evaporating temperature of the refrigerating evaporator 3 is reduced. Is lowered from -10 ° C. to about −15 ° C., and the switching valve 12 is operated so that the liquid refrigerant condensed in the condenser 8 is sent to the refrigeration expansion mechanism 9 via the heat transfer mechanism 11. At this time, the liquid refrigerant sent to the refrigeration expansion mechanism 9 is supercooled from a temperature close to the condenser 8 to a temperature close to the refrigeration evaporator 3. As a result, the amount of refrigerant supplied to the refrigeration evaporator 3 is reduced, the refrigeration capacity of the refrigeration evaporator 3 is reduced by the heat load of the heat transfer mechanism 11, and at the same time, the refrigeration capacity of the refrigeration evaporator 1 is reduced. The refrigerating capacity of the freezing room with respect to the refrigerating room is improved. Furthermore, the low-stage compressor 1
By increasing the number of rotations of the compressor 5 from the high-stage compressor 18 and adjusting the circulation amount of the refrigerant in accordance with the load of the refrigerator compartment and the freezer compartment, it is possible to cope with a larger change in load ballast.

In this embodiment, the low-stage compressor 15 and the high-stage compressor 18 are provided separately, but similar characteristics can be expected by installing a compression mechanism and a motor in the same shell. In addition, the pressures in the shells are matched so that the lubricating oils of the low-stage compressor 15 and the high-stage compressor 18 do not become unbalanced.
It is desirable to provide an oil equalizing pipe connecting both lubricating oil phases.

[0040]

As described above, according to the present invention, in a refrigerant two-stage compression type refrigeration system having a plurality of evaporators having different evaporation temperatures, such as a refrigerator-freezer, when the load of the freezing room is suddenly increased. Using a capacity control method that reduces the amount of heat exchange between the refrigerating compartment and the refrigerating evaporator to lower the evaporating temperature of the refrigerating evaporator and increases the subcooling amount of the liquid refrigerant supplied to the refrigerating evaporator. This makes it possible to reduce the refrigerant circulation amount of the refrigerating evaporator with respect to the refrigerating evaporator without lowering the temperature of the refrigerating room, and then increase the operation rate or the number of revolutions of the compressor to increase the refrigerant in accordance with the load of the freezing room. By adjusting the circulation amount, it is possible to cope with a change in the load balance of the freezer compartment with respect to the refrigerator compartment.

[Brief description of the drawings]

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

FIG. 2 is a refrigerant circuit diagram of a refrigeration cycle according to Embodiment 2 of the present invention.

FIG. 3 is a refrigerant circuit diagram of a refrigeration cycle according to a third embodiment of the present invention.

FIG. 4 is a refrigerant circuit diagram of a conventional refrigeration cycle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Evaporator for freezing 3 Evaporator for refrigeration 6 Low stage compression mechanism 7 High stage compression mechanism 11 Heat transfer mechanism 12 Switching valve 13 Gas-liquid separator 15 Low stage compressor 18 High stage compressor

Claims (3)

[Claims] 1. A refrigerating evaporator for cooling a refrigerating compartment, a refrigerating evaporator for cooling a refrigerating compartment, a low-stage compression mechanism for compressing a return gas refrigerant from the refrigerating evaporator, and the refrigerating evaporator. A high-stage compression mechanism that compresses a mixture of the return gas refrigerant from the device and the discharge gas refrigerant of the low-stage compression mechanism; a condenser that condenses the discharge gas refrigerant of the high-stage compression mechanism; and a condenser that condenses in the condenser. A refrigeration expansion mechanism for reducing the pressure of the liquid refrigerant and supplying the same to the refrigeration evaporator; and a supercooling control for controlling the subcooling temperature by cooling the liquid refrigerant supplied to the refrigeration evaporator with the refrigeration evaporator. Means and a refrigeration expansion mechanism for decompressing the liquid refrigerant condensed in the condenser and supplying the refrigerated evaporator to the refrigeration evaporator. The amount of heat exchange in the evaporator A refrigerating apparatus using a control method for lowering an evaporating temperature and increasing a subcooling amount of a liquid refrigerant supplied to the refrigerating evaporator. 2. A refrigerating evaporator for cooling a refrigerating room, a refrigerating evaporator for cooling a refrigerating room, a low-stage compression mechanism for compressing a return gas refrigerant from the refrigerating evaporator, and the refrigerating evaporator. A high-stage compression mechanism that compresses a mixture of the return gas refrigerant from the device and the discharge gas refrigerant of the low-stage compression mechanism; a condenser that condenses the discharge gas refrigerant of the high-stage compression mechanism; and a condenser that condenses in the condenser. A refrigeration expansion mechanism for decompressing a liquid refrigerant and supplying the refrigeration evaporator to the refrigeration evaporator; and a gas-liquid separator for separating an outlet refrigerant of the refrigeration evaporator into gas and liquid and supplying a gas refrigerant to the high-stage compression mechanism. A refrigeration expansion mechanism that decompresses the liquid refrigerant separated by the gas-liquid separator and supplies the refrigeration evaporator to the refrigeration evaporator; and decompresses the liquid refrigerant condensed by the condenser and supplies it to the refrigeration evaporator. In the refrigerating device having the second refrigerating expansion mechanism, When the temperature increases rapidly, the amount of heat exchange between the refrigerating chamber and the refrigerating evaporator is reduced to lower the evaporating temperature of the refrigerating evaporator, and the amount of liquid refrigerant passing through the second refrigerating expansion mechanism is reduced. Refrigeration equipment using the method. 3. A low-stage compressor comprising a low-stage compression mechanism and a low-stage variable-speed motor, and a high-stage compressor comprising a high-stage compression mechanism and a high-stage variable-speed motor. 2
A refrigeration apparatus according to claim 1.