The separator can return most of the compressor lubricating oil taken out from the compressor discharge port, and a small part of the oil must be circulated through the system to return from the compressor suction port together with the refrigerant. Gradually collecting oil in the system will still cause the heat exchange efficiency to drop and the compressor to lack oil and other faults. On the contrary, for refrigerants that are slightly soluble in oil, such as R404a, the oil-passing separator will increase the saturation of the oil-soluble refrigerant in the refrigerant. For large-scale systems, because the system pipeline is relatively thick, the oil return is relatively smooth, and the oil volume is large, so the oil distribution separator is more suitable. For small systems, the smooth return of the system oil is the key to the oil circuit. The oil separator of little effect.
Evaporation pressure regulating valves are generally used in dehumidification systems to control the evaporation temperature so that the evaporator does not frost. However, in the unipolar circulation system, the use of the evaporative pressure regulating valve must be connected to the refrigeration return air solenoid valve, which makes the pipeline structure complicated and is not conducive to the smoothness of the system. At present, most test chambers are not equipped with evaporative pressure regulating valve.
The heat exchanger has three advantages. First, it can supercool the condensed refrigerant and reduce the amount of advance vaporization in the pipeline. Second, it can fully vaporize the return refrigerant and reduce the risk of liquid hammer. Third, it can improve the system. effect. However, the access of the heat exchanger complicates the piping of the system. If the piping layout is not careful about the process, the pipe loss will be increased. It is not conducive to the product configuration of Wuhan Huawei constant temperature and humidity test box.
For the refrigeration system of the constant temperature and humidity test chamber with the characteristics of variable working conditions, the gas-liquid separator is one of the effective means to avoid liquid shock, and it can also adjust the cooling capacity appropriately. However, the gas-liquid separator also cuts off the oil return of the system, so the oil separator must be installed to install the gas-liquid separator. For the unit composed of Taikang hermetic compressors, the gas-liquid separator can be omitted because there is an appropriate buffer space in the air return port, which can play a certain role in gasification. For units with limited installation space, thermal bypass can be set up to vaporize excess return liquid.
The cooling capacity PID control has a significant effect on energy saving in operation. Not only that, in the normal temperature (about 20°C) section where the temperature field index of the heat balance method is relatively poor, the cooling capacity PID control system can achieve the ideal index; in terms of constant temperature and humidity It can also reflect a good effect, so the cooling capacity PID control is already the leading technology in the refrigeration system of the ring test product. The cooling capacity PID control is divided into two types: time proportional and opening proportional. Time proportional is to control the ratio of opening and closing of the refrigeration solenoid valve in a time period, and opening proportional is to control the conduction amount of the electronic expansion valve. However, in the time proportional control, the life of the solenoid valve is a bottleneck. At present, the best solenoid valves on the market are estimated to have a life span of only 3 to 5 years. Therefore, it is necessary to calculate whether the maintenance cost is lower than the energy saving and consumption reduction. The electronic expansion valve in the proportional control of the opening degree is currently expensive, and it is inconvenient to purchase on the market. Because it is also dynamic balance, it also involves the problem of life.