Air-cooled chiller expansion valve how to choose? How to determine the pressure of high and low pressure?

Industrial chiller, screw chiller, air-cooled chiller, chiller expansion valve how to choose and install: the choice of expansion valve air-cooled chiller cooling system performance plays an important role, the right choice The expansion valve will maximize the use of the evaporator and match the evaporator to the thermal load. It is one of the four components of the refrigeration system and is an important device for regulating and controlling the flow of refrigerant and pressure into the evaporator.

First, the choice of thermal expansion valve In the air-cooled chiller refrigeration system, the expansion valve selection and installation is very important, only the correct choice and installation can ensure the normal operation of the unit. Therefore, when selecting the expansion valve, we can use the appropriate thermal expansion valve according to the evaporator load and the evaporation temperature. The capacity of the commonly used expansion valve is about 20% greater than the heat load of the evaporator. For small chiller refrigeration systems, gas-filled thermal expansion valves are generally used, and medium-sized air-cooled chiller refrigeration systems mostly use adsorption-injection or mixed-fill expansion valves.

Second, the expansion valve installation 1, chiller expansion valve installed in front of the evaporator, usually installed in a vertical position. Considering the ease of installation and maintenance, the cold loss is small and should be as close to the evaporator inlet as possible.
2. The working condition of the air-cooled chiller expansion valve has a direct relationship with the installation location of the temperature sensing package. Because, the expansion valve completely adjusts the opening size of the expansion valve depending on the temperature change of the temperature sensing package. The temperature sensor package is installed on the chiller evaporator outlet pipe. As the evaporator outlet pipe grows, its superheat increases gradually. Therefore, the location of the expansion valve bulb is directly related to the volume of the expansion valve. In general, the temperature-sensing package is installed more than 1.5m away from the suction port of the compressor. When the fluid supply volume cannot meet the system requirements, the expansion valve screw must be adjusted to adjust the fluid supply.
3, when the temperature expansion bag of the expansion valve is installed, close contact with the suction pipe is required. The contact surface requires clean, small thermal resistance, and is free from interference from outside temperature and other factors. The temperature-sensing bag and gas return pipe are usually tied with metal straps and fastened with bolts. At the same time, heat-insulating and moisture-proof insulation layers should be wrapped outside the temperature-sensing bag and pipe to reduce external disturbances, so that the thermal expansion valve can work stably and adjust sensitively.

How to judge the high and low pressure of the air-cooled chiller: The standard chiller high pressure pressure is best shown in 12.5 ~ 15k g/cm2, air-cooled 14 ~ 17k g/cm2 is the best, but not higher than 19.5kg/cm2, When the water-cooled pressure is higher than 19.5kg/cm2 and the air-cooled pressure is higher than 24kg/cm2, the high-voltage switch will automatically trip. Please follow the instructions below: Low pressure is best at 3.1-4.5kg/cm2, but not lower In 2k g/cm2, less than 2k g/cm2 low pressure automatic trip, please follow the instructions (b) processing.
Explain (a)
When the condenser of the chiller is poorly cooled, the efficiency of the compressor becomes lower and the operating current increases. When the high pressure of the air-cooled chiller rises to 24kg/cm2 and the high pressure of the water-cooled chiller rises to 19.5kg/cm2, the compressor is protected by the high-voltage switch and the compressor is automatically stopped. At this time, high pressure will appear. Overload alarm and display fault code or fault indication. At this time, it is necessary to check whether the circulating water of the cooling tower is normal, whether the cooling water temperature is too high, whether the cooling tower fan, the pump is running, and whether the cooling water valve is fully opened (air-cooled chiller is checked Whether the radiator is dirty or not, and then confirm that all are normal, then press the reset button (REST) ​​or turn off the chiller to start normal operation. If high-pressure overload alarms occur frequently, it is necessary to arrange the manufacturers to clean the chiller condensers as soon as possible.
Explanation (2)
1. When the water temperature of the chiller is above 5°C, when the low pressure gauge pressure is less than 2k g/cm2, it means that the refrigerant is insufficient. Therefore, the leaking refrigerant must first be trapped, then the dry filter must be replaced to revacuate. Supplement with appropriate refrigerants.
2. If it is found that the leakage refrigerant is partially immersed in water, the chiller must be immediately stopped and the water in the tank must be eliminated. The manufacturer should be informed as soon as possible to send the technicians to handle the maintenance, so as to prevent the compressor from drawing refrigerant water into the refrigeration system. Damage

Johnson Machinery Tips: If the thermal expansion valve and the cooling system do not match, it will make the system's refrigerant flow time and time, so that the thermal expansion valve cooling capacity when large and small. When the cooling capacity is too small, the evaporator will be insufficient for liquid supply, resulting in excessive heat, which will have an adverse effect on the unit system performance. When the refrigerating capacity is too large, oscillation may occur, and the evaporator may intermittently excessively supply the liquid, causing the compressor suction pressure to fluctuate violently, and even liquid refrigerant may enter the compressor, causing a liquid strike (wet stroke) phenomenon.