The capacity of a given expansion valve is determined by what two basic components?

The capacity of a given expansion valve is fundamentally determined by the mass flow rate and the net refrigeration effect.

The mass flow rate refers to the amount of refrigerant that passes through the expansion valve in a given time, which is crucial because an insufficient flow can lead to inadequate cooling, while excessive flow can cause the system to overcool.

On the other hand, the net refrigeration effect is the total heat absorbed by the refrigerant during its evaporating process; it reflects the ability of the refrigerant to absorb heat from the environment and effectively cool the space. The combination of these two components is essential in defining how well the expansion valve will perform in regulating the refrigerant flow to meet the cooling demands of the system.

While other components like superheat and sub-cooling play important roles in the overall efficiency and operation of a refrigeration system, they do not directly define the capacity of the expansion valve in the same way that mass flow rate and net refrigeration effect do. Superheat indicates how much the refrigerant is heated above its boiling point, and sub-cooling suggests how much it is cooled below its condensing point, but they are more related to system performance than to the capacity specification of the expansion valve itself.