JPS6337864B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a two-temperature evaporative refrigeration system that implements a control system with high operating efficiency.

Conventionally, in a two-temperature evaporative refrigeration cycle, the first
As shown in the figure, a compressor 1, a condenser 2, a first pressure reducer 3,
A refrigeration cycle 7 in which a first cooler 4 and a first cooler 4 are sequentially connected, and a second cooler 6 having a low evaporation temperature is further connected via a second pressure reducer 5 is common. FIG. 2 shows an example in which this refrigeration cycle is applied to a refrigerated open case with an internal temperature of 0 to 2°C. The two-temperature refrigerated open storage case shown in the figure includes an insulating box 11 having an opening on the front, an inner case 17 that forms an air passage 12 inside the box and stores stored items, and further includes an inner case 17 inside which forms an air passage 12 to store stored items. An internal air blower 14, a dehumidifying cooler B with a high evaporation temperature, and a main cooler A with a low evaporation temperature are installed respectively, and a cold air outlet 15 is installed at the upper front of the air passage 12, and an inlet 16 is installed at the lower part. are installed to form an air curtain.

The dehumidifying cooler B is the first refrigeration cycle 7 in FIG.
Corresponding to the cooler 4, the cooler surface temperature is set to around 0°C (0°C or higher). Further, the main cooler A corresponds to the second cooler 6, and the cooler surface temperature is set to approximately -10°C to -15°C.

Here, the hot and humid air sucked in by the internal blower 14 has a surface temperature of the cooler near 0°C (0°C).
Dehumidification is carried out in the form of water by dehumidifying cooler B, which is set at a temperature of at least 10°C. The dehumidified air with reduced moisture is further cooled to a predetermined temperature (approximately -5°C) by the main cooler A, and then blown into the refrigerator interior 13 from the cold air outlet 15 at the top of the show case. Cool the inside to the required temperature (0-2°C).
The air that has cooled the inside of the refrigerator partially draws in outside air, is sucked in again through the suction port 16, and the same circulation is repeated thereafter. Further, the cold air blown out from the outlet 15 forms an air curtain at the front opening to prevent outside air from entering the inside 13 of the refrigerator. In a two-temperature evaporative refrigerating case like this one, the amount of frost on the main cooler A is reduced by the deskewing action of the dehumidifying cooler B, and the number of times of defrosting can be reduced. This has the effect of reducing damage to stored goods due to rising. However, in the conventional two-temperature evaporative refrigeration open case like this example, in order to keep the surface temperature of the dehumidifying cooler B always above 0°C, for example, an evaporative pressure regulating valve (not shown) is installed in the refrigeration cycle. When the temperature inside the refrigerator is low because it is kept constant using a mechanism, or when the ambient air temperature is low and the intake air temperature drops to nearly 0℃, the difference between the dehumidifying cooler B and the air temperature. As a result, the dehumidifying effect of the dehumidifying cooler B is drastically reduced and the amount of frost formed on the main cooler A is increased. In addition, if a mechanism for adjusting the evaporation pressure such as the above-mentioned evaporation pressure adjustment valve is not provided, the surface temperature of the dehumidifying cooler B is set to approximately 0°C during normal operation when the intake air temperature is high, and the air Moisture is condensed and dehumidified in the form of water, but when the intake air temperature is low, such as when the internal temperature is low or the ambient air temperature is low, the evaporation temperature of dehumidifying cooler B decreases. When the surface temperature of the dehumidifying cooler drops below 0°C, some of the water freezes or forms frost on the surface of the cooler, clogging the cooler, lowering the evaporation pressure, and reducing operating efficiency. . As another conventional example, the dehumidifying cooler B and the main cooler A are combined with a compressor 21, as shown in FIG.
21', condenser 22, 22', pressure reducer 23, 23',
When configured with two independent refrigeration cycles 25 and 25' formed by coolers 24 and 24', the coefficient of performance of the refrigeration cycle 25 connected to dehumidifying cooler B, which has a higher evaporation temperature, is higher. So,
The operating efficiency of the entire refrigeration system is increased. However, in this case as well, when the refrigeration load decreases, it becomes difficult to set the surface temperature of dehumidifying cooler B to approximately 0°C, and as in the conventional example shown in Fig. 1, dehumidifying cooler B
As frost forms on the dehumidifying cooler B, the evaporation temperature of the dehumidifying cooler B eventually decreases, which not only makes it difficult to maintain efficient operation for a long time, but also has the drawback that the operating range of the cooler with a high evaporating temperature is narrow. It was hot.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and when frost formation occurs in dehumidifying cooling with a high evaporation temperature depending on operating conditions such as ambient conditions and internal temperature conditions, as in the above-mentioned conventional example, However, while maintaining dehumidification performance and reducing frost formation on the main cooler,
It is an object of the present invention to provide a method of operating a two-temperature evaporative refrigeration system with high operating efficiency by increasing the operating ratio and heat exchange ratio of the cooler on the side where the evaporation temperature is higher.

An embodiment of the present invention will be described below based on FIG. 4. In the figure, a first compressor 31, a condenser 3
2. The first solenoid valve 33, the first pressure reducer 34, and the first cooler 35 are connected in a ring to form a main refrigerant circuit, and the outlet side of the condenser 32 is branched to form a second solenoid valve 37. , the second pressure reducer 38, the second cooler 39, and the second compressor 36 are connected in series, and the discharge side of the second compressor 36 is further connected to the discharge side path of the first compressor 31 to form an auxiliary refrigerant circuit. The evaporation temperature of the second cooler 39 is set higher than the evaporation temperature of the first cooler 35 to perform the freezing operation.

Further, the second compressor 36 is forced to operate intermittently, and the first compressor 31 operates intermittently depending on the refrigeration load.

A case where the refrigeration cycle of the above embodiment is applied to the refrigerating case shown in FIG. 2 will be explained. Second
In the figure, the dehumidifying cooler B is the second
The main cooler A corresponds to the cooler 39 and the first cooler 35 of the refrigeration cycle 40 . Internal blower 1
The hot and humid air sucked in by the air filter 4 is dehumidified in the form of water or frost by the dehumidifying cooler B whose evaporation temperature is set at around 0° C., including 0° C. or lower. As a result, the amount of frost on the main cooler A is reduced, and the number of times of defrosting can be reduced, so that fluctuations in temperature inside the refrigerator due to defrosting can be reduced.

Furthermore, in this embodiment, since the second compressor 36 is forced to operate intermittently, as described below, the operating efficiency is reduced due to a decrease in evaporation temperature and an increase in ventilation resistance that occur when frost forms on the dehumidifying cooler B. It is also possible to prevent the decrease.

For example, if the operation of the second compressor 36 is stopped by an operation command from a timer (not shown) or the like after operation for a certain period of time (for example, 30 minutes), the cooling action of the dehumidifying cooler B39 will stop, and the main cooler A35 alone will not work. Since the refrigerating capacity is insufficient, the temperature of the intake air rises to 0° C. or higher, and the frost adhering to the surface of the dehumidifying cooler B melts. After stopping for a certain period of time (for example, 3 minutes), the operation of the second compressor 36 is restarted, and by repeating the above operation, an increase in the amount of frost formed on the dehumidifying cooler B is prevented, so that the ambient air temperature Even when the intake air temperature drops to around 0℃, such as when the temperature is low or the internal temperature is low, dehumidifying cooler B can perform efficient dehumidification for a long time, and the evaporation pressure can be maintained for a long time due to increased frost formation. , prevent the decline, and the second
A decrease in the operating efficiency of the compressor 36 can be prevented. Further, since the operating range of the dehumidifying cooler B can be expanded to a low evaporation temperature region where moisture forms frost on the surface of the dehumidifying cooler B, the heat exchange ratio of the dehumidifying cooler B to the total amount of heat exchanged can be set to be large. In addition, the first compressor 31, which has a low evaporation temperature and a poor coefficient of performance, operates intermittently depending on the load, while the operating range of the second compressor 36, which has a high evaporation temperature and a good coefficient of performance, is expanded to a lower load region. Since the operating ratio of the compressor can be expanded, there is also the effect of increasing the operating efficiency of the refrigeration system.

Furthermore, since the condenser 32 is used in common to form the refrigeration cycle, when the first compressor 31 stops, the amount of refrigerant passing through the condenser 32 decreases by the amount discharged from the first compressor 31, so the condensing pressure That is, the discharge pressure is reduced, the coefficient of performance of the second compressor 36 is improved, and the operating efficiency of the refrigeration system as a whole can be further improved. In this embodiment, intermittent operation is performed at a fixed period using a timer or the like, but intermittent operation may be performed using a detection element such as a dehumidification sensor or a temperature sensor.

In addition, in the present invention, the surface temperature of the dehumidifying cooler B is 0°C.
Even when the settings above are set to prevent frost formation, the effectiveness of the condenser at low load, the second
Effects such as improved operating efficiency due to the high evaporation temperature of the cooler and reduction in pressure loss due to the parallel connection of the two coolers can be obtained. In addition, even if the surface temperature of dehumidifying cooler B is below 0°C and the inlet temperature is always below 0°C, dehumidifying cooler B may be
The same effect can be obtained by stopping the operation of the dehumidifying cooler B, blocking the front and rear of the dehumidifying cooler B with a damper, defrosting it with a heater, etc., and bypassing the dehumidifying cooler B in the meantime and guiding the cold air to the main cooler A. The effect of this can be obtained.

As explained above, according to the present invention, a refrigeration cycle having two coolers with different evaporation temperatures and two compressors can be combined with a common condenser to achieve evaporation. 2nd place with higher temperature
The compressor is forced to operate intermittently, with operation stopped at regular intervals, and the first compressor is operated intermittently depending on the refrigeration load, so that the compressor is not only dehumidified as water in the cooler with a higher evaporation temperature. This has the effect that high operating efficiency can be obtained even under operating conditions that cause frost formation.

[Brief explanation of the drawing]

Figures 1 and 3 are block diagrams of a conventional two-temperature evaporative refrigeration cycle, Figure 2 is a cross-sectional structural diagram of a two-temperature evaporative refrigeration case, and Figure 4 is a block diagram of a refrigeration cycle showing an embodiment of the present invention. be. 31...first compressor, 32...condenser, 33...
...first solenoid valve, 34...first pressure reducer, 35...first cooler, 36...second compressor, 37...second solenoid valve, 38...second pressure reducer, 39...th 2 cooler, 40... Refrigeration cycle, A... Main cooler, B
...Dehumidifying cooler.

Claims (1)

[Claims] 1 A main refrigerant circuit that has a second cooler with a high evaporation temperature and a first cooler with a low evaporation temperature, and connects the first compressor, the condenser, the first pressure reducer, and the first cooler in an annular manner; The secondary compressor branches the outlet side path of the compressor, connects the second pressure reducer, second cooler, and second compressor in series, and further connects the discharge side of the second compressor to the discharge side path of the first compressor. In the operation of a two-temperature evaporative refrigeration system equipped with a refrigerant circuit, the second compressor performs a controlled intermittent operation in which the operation is stopped at fixed intervals using a timer, and the first compressor operates so that the cooling space reaches the desired temperature. 1. A method of operating a refrigeration system, characterized in that a thermostat provided in a cooling space performs intermittent operation according to the refrigeration load.