Factors affecting the cooling effect of high and low temperature testing machine
If there is an abnormality in the high and low temperature test unit, it will cause the heat to be unable to be discharged, and in serious cases, it will shut down. What are the reasons for the poor refrigeration effect of the high and low temperature test set?
The working principle of high and low temperature testing machine refrigeration is that the refrigerant is compressed into a high temperature and high pressure gas in the compressor, and then enters the condenser. The refrigerant releases heat and condenses into liquid. After the dryer to remove moisture, high-pressure liquid refrigerant through the expansion valve throttling and reduced to low-pressure wet steam, and then into the evaporator to absorb heat and vaporize the low-pressure gas, low-pressure gas into the compressor to form a cycle.
From the principle can be seen, the impact of high and low temperature testing machine with the compressor, condenser, expansion valve and evaporator, and in the refrigeration cycle, the oil-water separator is also a factor affecting the refrigeration effect.
1、Expansion valve
If the high and low temperature test unit is running, the equipment will shut down due to low inlet pressure. If the amount of refrigerant is sufficient, the expansion valve will be blocked or frozen, resulting in the refrigerant not being able to enter the evaporator smoothly, then the alarm will be raised due to low inlet pressure. By checking the drier cartridge for impurities, you can determine if the expansion valve is at fault. Improper overheating of the expansion valve can also affect the abnormal response of the unit. For example, the adjusting screw size is too small, which will lead to less refrigerant entering the evaporator, resulting in low pressure and poor cooling effect.
2, oil separator failure
The role of the oil separator is to separate the lubricant and refrigerant discharged together. The top of the oil separator is equipped with a filter element. If the filter element fails, it will lead to oil separation failure. Through observation, you can determine whether there is lubricant in the refrigerant, and then determine whether it is caused by the failure.
3, evaporator leakage blockage fault
The evaporator is a heat exchange component, low temperature chilled water from the evaporator into the chilled water cycle. If the evaporator leakage or clogging, will lead to insufficient chilled water flow, low compressor inlet pressure and alarm shutdown. The solution is to find out the leakage point through the water pressure test and troubleshoot the problem.
4, compressor failure
For screw compressor, the compressor load adjustment is through the slide valve to adjust the working volume, the slide valve movement makes the bypass hole open and close. For the position of the slide valve, adjust the zero position of the slide valve can make the compressor back to normal.
5, summarize
Caused by high and low temperature experimental machine does not refrigerate more factors, through the high and low temperature experimental unit expansion valve, evaporator, oil separator and compressor body slide valve and other factors affecting the inspection and analysis, you can accurately determine the high and low temperature experimental unit working abnormally, and then eliminate the hidden dangers, to ensure the safe operation of the device.