What determines the low side pressure in a refrigeration system?

The low side pressure in a refrigeration system is primarily determined by the evaporator flow rate. This is because the evaporator's function is to absorb heat from the surroundings, creating low-pressure conditions as the refrigerant evaporates within it. The rate at which the refrigerant evaporates directly affects the pressure in the evaporator; as more heat is absorbed and more refrigerant turns into vapor, the pressure will adjust accordingly.

A higher flow rate through the evaporator allows for more refrigerant to evaporate, which can lead to lower pressure on the low side of the system. Conversely, if the flow is restricted, the pressure might rise since the refrigerant would not be vaporizing efficiently.

In contrast, while the condenser flow rate, expansion valve size, and compressor speed each play roles in the overall efficiency and operation of the refrigeration system, they are not the primary determinants of the low side pressure. The condenser flow affects the high side pressure, the expansion valve size influences the amount of refrigerant entering the evaporator, and the compressor speed impacts the overall system performance but does not directly govern the low side pressure like the evaporator does.