In a vapor compression ammonia system, how should the refrigerant be charged?

In a vapor compression ammonia system, the refrigerant should be charged in the liquid phase to ensure optimal system performance. Charging the system with liquid refrigerant allows for proper control of the system's refrigerant circuits and helps in establishing the correct pressure and temperature conditions within the evaporator and condenser.

When the refrigerant is charged as a liquid, it ensures that it is being introduced into the system at the right point, typically at the service port on a receiver or the liquid line. This process minimizes the risk of introducing vapor, which can lead to insufficient cooling or inefficiencies in the system. A liquid charge aids in maintaining the specific thermodynamic conditions required for effective heat exchange, particularly in the evaporator where the refrigerant must easily absorb heat from the refrigerated space.

Additionally, charging the refrigerant in the liquid state helps to prevent potential issues such as flooding of the compressor or reduced efficiency due to vapor not having the same thermal capacity as the liquid. Therefore, liquid charging is critical for achieving the desired operational efficiency and effectiveness of the ammonia refrigeration system.