JPS6045337B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a refrigeration system having an air-cooled condenser.
In particular, it attempts to significantly improve performance by adding an auxiliary compressor.

Condensing pressure changes depending on the ambient air temperature. For example, when the ambient temperature is low, such as during winter, the condensing pressure decreases, the pressure difference between high pressure and low pressure becomes smaller, and the amount of refrigerant passing through the expansion valve decreases significantly. This results in a lack of cooling capacity. When the condensing pressure further decreases, the pressure drop due to friction loss inside the liquid line is offset by heat entering from outside the pipe, causing flash gas to easily occur in the liquid refrigerant, further impairing the function of the expansion valve. For this reason, conventionally, means have been taken to keep the condensing pressure constant by controlling the condensing pressure as shown in FIG. 1 is a compressor, 2 is a condenser, 3 is an expansion valve, 4 is an evaporator, 5 is an inlet pressure regulating valve 5, and 6 is an outlet pressure regulating valve.

Here, the inlet pressure regulating valve 5 is set to a set condensing pressure, for example, 15.9/ai9, and the outlet pressure regulating valve 6 is set to a pressure lower than the setting of the inlet pressure regulating valve 5 by about 0.59/CffL. The operation of the cycle is such that the refrigerant gas discharged by the compressor 1 first flows into the condenser 2 and is liquefied there. However, when the ambient air temperature is high, the condensation pressure increases to match the heat transfer performance of the condenser. When the pressure rises above the set pressure of the inlet pressure regulating valve 5, the valve is closed and the flow rate of refrigerant to the liquid pipe 9 increases. At the same time, the pressure inside the liquid pipe 9 also rises, and when it exceeds the set value of the outlet pressure regulating valve 6, the passage is stopped. Conversely, as the ambient temperature decreases, the condensation pressure also decreases. For this reason, the inlet pressure regulating valve 5 throttles the valve opening degree, accumulates the condensed liquid refrigerant in the condenser 2, and reduces the effective heat transfer area.
When the condensing pressure is increased to the set pressure, the outlet pressure regulating valve 6 is opened to allow the gas refrigerant to flow, thereby preventing a pressure drop at the outlet of the inlet pressure regulating valve 5. As described above, unless the ambient temperature is extremely high, the condensing pressure is kept constant even if the ambient temperature changes, so that the expansion valve 3 always maintains its normal function. However, as shown in FIG. 2, the coefficient of performance under such operating conditions has a characteristic such as a-b. Section a-b is a state in which the ambient air temperature is extremely high and the condensing pressure exceeds the set pressure. Section bb is condenser 2
This is a state in which the ambient air temperature is low, with liquid refrigerant stored inside and maintained at a set pressure by a control valve. This a-b-b
The characteristics are that the operation of the expansion valve 3 is extremely inefficient compared to the performance a-b-c when the valve opening is adjusted according to changes in the pressure difference between high and low pressures without condensing pressure control. It's summery. In particular, in refrigeration equipment that is constantly operated,
Despite the fact that the load is reduced in the winter, the current situation is that condensing pressure is increased, leading to inefficient operation and increasing operating costs. The present invention was invented in view of the above-mentioned drawbacks, and is particularly aimed at improving operational efficiency.

The structure of the present invention is that a first pressure reducing device, a gas-liquid separator, and a second pressure reducing device are provided between the condenser and the evaporator, and an auxiliary compressor is provided in parallel with the main compressor. A check valve that flows only to the suction side of the auxiliary compressor is interposed in the path, and the upper part of the gas-liquid separator is connected to the suction side of the auxiliary compressor through a path that includes a solenoid valve. When the temperature is high, the solenoid valve is opened, and the gas refrigerant in the upper part of the gas-liquid separator joins the discharge gas of the refrigerant circuit through the auxiliary compressor, and when the ambient air temperature is low, the solenoid valve is closed. It has the feature that the auxiliary compressor is operated in parallel with the main compressor. An embodiment of the present invention will be explained based on FIG.

1 is the main compressor, 2 is the condenser, 11 is the high pressure float valve, 1
2 is a gas-liquid separator, 3 is an expansion valve, 4 is an evaporator, 13 is an auxiliary compressor, 14 is a solenoid valve, and 15 is a check valve, which are connected by piping as shown.

The operation of this refrigeration cycle is performed as follows.
First, high-temperature, high-pressure refrigerant gas discharged from the main compressor 1 enters the condenser 2 through the pipe 7. The condensed liquid is then reduced in pressure to an intermediate pressure between high and low pressures by the high-pressure float valve 11 of the first pressure reducing device, and flows into the gas-liquid separator 12, and the liquid flows into the gas-liquid separator. from the bottom of the tank, through the expansion valve 3 of the second pressure reducing device, and after passing through the evaporator 4, returns to the suction side of the main compressor 1,
Form a refrigeration cycle. On the other hand, when the refrigerant gas accumulated in the upper part of the gas-liquid separator 12 and the ambient air temperature is high, the solenoid valve 14 in the pipe 16 connecting the upper part of the auxiliary compressor liquid 12 and the suction and inlet of the auxiliary condenser 13 is opened, and by the action of the auxiliary compressor 13, it is merged into the discharge side of the main compressor 1 again. At this time, since the pressure inside the pipe 18 is lower than the pressure inside the pipe 16,
The check valve 15 is closed and does not form a flow path. In the above operating state, the dryness of the refrigerant flowing into the evaporator 4 decreases and the amount of effective refrigerant increases, resulting in an increase in refrigeration capacity, and the gas refrigerant that is not used for cooling is efficiently extracted at intermediate pressure with high density. Therefore, the product coefficient is represented by a''-c'' in FIG. 4, which is higher than the characteristic a-c of the single-stage cycle. Note that the section bb shows the characteristics when condensing pressure control as shown in FIG. 1 is performed. Furthermore, since the expansion valve 3 operates based on the difference between the intermediate pressure and the low pressure, the valve opening degree is set to be large so that it can be used with a lower differential pressure than in the single-stage cycle shown in FIG. Next, when the ambient air temperature is low, the condensing pressure and intermediate pressure also decrease, and the pressure difference across the expansion valve 3 decreases, causing the expansion valve 3 to no longer follow the load. In this case, the solenoid valve 14 The opening and closing of the solenoid valve 14 may be switched depending on changes in ambient temperature or condensing pressure. When the electromagnetic valve 14 is closed, the auxiliary compressor 13 is installed in parallel with the main compressor 1, and the refrigerant gas flows to the discharge side of the main compressor 1 via the pipe 18 and the check valve 15. As a result, the pressure drop at the high pressure float valve 11 is almost eliminated, and the expansion valve 3
A high and low pressure that is higher than the intermediate and low pressure when the solenoid valve 14 is open acts on the front and rear sides. In this way, the expansion valve 3 can be operated efficiently even down to a lower temperature region. The coefficient of performance switches to a single-stage cycle at α, and thereafter cm
It is operated with d characteristic. In addition, if the liquid piping 9 is long and there is a possibility of pressure loss or heat loss, as shown by the broken line in Figure 3,
A subcooler 20 that subcools the refrigerant may be provided. That is, the liquid pipe 9 is branched near the outlet of the gas-liquid separator 12, and this branch pipe 21 is connected to the suction pipe 10 through a subcooler expansion valve 19 and a subcooler 20 arranged in a heat exchange state with the liquid pipe 9. . Further, in both of the above embodiments, a refrigeration cycle having an air-cooled condenser was particularly described, but the present invention is also applicable to a water-cooled condenser in which the cooling water temperature changes. As explained above, according to the present invention, the expansion valve 3
The expansion valve 3 can guarantee the necessary flow rate as a result of maintaining a large front and rear pressure and suppressing the generation of flash gas to the liquid in the liquid line.

Therefore, compared to the conventional single-stage cycle performance a-bb-b, the performance is a'-c''-cmd, and the performance in the low temperature range is significantly improved.

[Brief explanation of drawings]

Figure 1 is a cycle diagram of a conventional refrigeration system, Figure 2 is a diagram showing its coefficient of performance, Figure 3 is a cycle diagram of a refrigeration system showing an embodiment of the present invention, and Figure 4 is a coefficient of performance. FIG. 1... Main compressor, 2... Condenser, 3.
...Expansion valve (first pressure reducing device), 4...Evaporator, 11...High pressure float valve (first: pressure reducing device)
, 12... Gas-liquid separator, 13... Auxiliary compressor, 14... Solenoid valve (flow path switching means), 15...
... Check valve (flow path switching means), 19 ... Subcooler expansion valve, 20 ... Subcooler, 21.
...branch pipe.

Claims (1)

[Claims] 1. A main refrigerant circuit that communicates in an annular manner with the main compressor, condenser, first pressure reducing device, gas-liquid separator, second pressure reducing device, and evaporator, and an auxiliary compressor that is connected via piping in parallel to the main compressor. , a path connecting the gas phase section at the top of the gas-liquid separator to the suction side of the auxiliary compressor, and a path connecting the suction side of the auxiliary compressor to the suction side path of the main refrigerant circuit or the path at the top of the gas-liquid separator. When the air temperature around the condenser is high, the gas refrigerant in the upper part of the gas-liquid separator is sent to the discharge side of the main compressor via the auxiliary compressor via the flow path switching means. A refrigeration system characterized in that, when the ambient air temperature is low, the auxiliary compressor is operated in parallel with the main compressor via the flow path switching means.