In air separation equipment, the generation of throttling effect refrigeration capacity is closely related to the compression process.
After air is compressed by a compressor, its pressure and temperature both increase. The compressed gas has high pressure energy and internal energy. The throttling effect of refrigeration is not only generated by the gas passing through the throttle valve. When throttling, the gas pressure decreases, the volume expands, the intermolecular distance increases, the molecular potential energy increases, and the molecular kinetic energy decreases, resulting in a decrease in gas temperature. When the low-temperature and low-pressure gas after throttling flows through the heat exchanger, it can absorb heat from the gas with higher temperature and cool the latter. After the low-temperature gas absorbs heat, its temperature returns to the temperature before throttling. The ability of low-temperature gas to absorb heat during this process is called its throttling effect cooling capacity.
The magnitude of the throttling effect cooling capacity can be determined by calculating the enthalpy difference before and after throttling. Due to the fact that the throttling process is an isentropic process (i.e. the enthalpy value of the gas remains unchanged before and after throttling), the cooling capacity is equal to the difference between the enthalpy value of the gas after throttling and the enthalpy value of the gas before throttling.
The throttling effect cooling capacity is a part of the total cooling capacity of the air separation equipment, and the other part of the cooling capacity is generated by the expander. In air separation equipment, throttle valves and expanders are used in conjunction to meet the requirements of refrigeration capacity.
