Refrigeration principle of ammonia coolers
Thread Content
In principle, the cooling mechanism of this ammonia cooler relies on boiling refrigeration using a heat exchange tank; as shown in the diagram, the pressure before the liquid ammonia valve is 11 bar, while the pressure behind the valve is -34 kPa. Moreover, after passing through the control valve, the pipe diameter increases significantly, and the pipe behind the valve is almost the same size as the pipe for gaseous ammonia at the top. Therefore, are the cooling mechanisms of this ammonia cooler 1) refrigeration through the throttling and vaporization of liquid ammonia, or 2) refrigeration through ammonia evaporation or boiling in a heat exchanger?
The removal of heat is achieved through the latent heat of vaporization of ammonia； The main function of the throttle valve is to reduce pressure; at lower pressures, the evaporation temperature of ammonia is also lower. This allows a temperature difference to be created in the evaporator, thereby transferring heat from the material to the liquid ammonia and causing it to evaporate. There is only a small amount of flashing behind the throttle valve.
Throttling has a relatively large cooling effect; no phase change occurs after heat exchange, thus maintaining material balance.
The pressure behind the control valve decreases, which lowers the evaporation temperature; at the same temperature, heat must be absorbed during evaporation to achieve a cooling effect