Cooling water inlet temperature is too low
Ultra-low temperature freezer for ultra-low temperature testing of aerospace equipment components As the temperature of the cooling water decreases, the compressor discharge pressure, exhaust temperature, and filter outlet temperature are reduced. The temperature remains the same, because the cooling water temperature has not dropped to the extent that it will affect the cooling effect. If the temperature of the cooling water drops to a certain level, the condensing pressure will also decrease, so that the pressure difference between the two sides of the thermal expansion valve will decrease, the flow capacity of the thermal expansion valve will also decrease, and the refrigerant will also decrease, so the cooling effect will be reduced. .
Cooling water inlet temperature is too high
If the temperature of the cooling water inlet is too high, the refrigerant will be too cold, the condensation temperature will be too high, the condensing pressure will be too high, the compressor pressure ratio will increase, the shaft power will increase, and the gas transmission coefficient will decrease, thus reducing the cooling capacity of the system. Therefore, the cooling effect of the ultra-low temperature freezer for ultra-low temperature testing of aerospace equipment components will be reduced and the temperature will rise.
Circulating pump does not turn
When the ultra-low temperature freezer for ultra-low temperature testing of aerospace equipment components is commissioned and operated, the system circulating water pump should be opened first. When the circulating water pump does not rotate, the temperature of the cooling water outlet and the temperature of the refrigerant outlet of the condenser rise more obviously. Due to the sharp decrease of the cooling effect of the condenser, the suction temperature and the exhaust temperature of the compressor also rise rapidly, and the condensation temperature The rise also causes the evaporation temperature to rise, but the extent of the rise in the evaporation temperature is not as large as the increase in the condensation temperature, so the refrigeration efficiency is lowered and the temperature is rapidly increased.
The fan does not turn
There are two reasons why the fan does not turn. First, the electrical fault, the control circuit is not connected; the second is the mechanical failure of the fan shaft.
When the ultra-low temperature freezer fan of the aerospace equipment component ultra-low temperature test does not turn, the temperature will rise, and the suction pressure and exhaust pressure of the compressor will decrease to some extent. After the fan is not turned, the heat exchange efficiency of the inner heat exchange coil is lowered, and the temperature rises when the heat load is constant.
The refrigerant in the heat exchange coil is insufficient in heat exchange, and its temperature is lowered relative to the original temperature, that is, the evaporation temperature becomes smaller, and the refrigeration coefficient of the system is lowered. The evaporator outlet temperature felt by the thermal expansion valve is also lowered, so that the opening of the thermal expansion valve becomes smaller and the refrigerant is correspondingly reduced, so the suction and exhaust pressures are all reduced. The overall effect of the reduction in refrigerant flow and the reduction in the refrigeration coefficient is to reduce the cooling capacity of the system.
The filter is blocked and the system is dirty. Under normal circumstances, dirty plugging often occurs at the filter. This is because the filter screen of the ultra-low temperature freezer filter for ultra-low temperature testing of aerospace equipment components blocks the passage section and filters out dirt and metal chips and other debris for a long time. And it was blocked.
These failures of ultra-low temperature freezer for ultra-low temperature testing of aerospace equipment components are still not too difficult. If we encounter unknown difficulties, we do not need our operators to challenge them, or they are solved by specialized technicians.