What is the primary phase for charging refrigerant in a vapor compression system?

The primary phase for charging refrigerant in a vapor compression system is the liquid phase. When refrigerant is charged into a system, its liquid state allows it to be efficiently introduced into the evaporator, where it will absorb heat and turn into vapor. Liquid refrigerant has a higher density and can be easily metered into the system, ensuring that the appropriate amount is injected without causing issues such as flooding or liquid slugging in the compressor.

In the context of the vapor compression cycle, starting with the liquid phase is essential for the system to operate effectively. This is because the vapor compression system relies on the refrigerant transitioning between liquid and gas states to absorb and release heat, which facilitates the cooling process. By charging the system with the refrigerant in its liquid form, the operator can ensure proper functionality and efficiency of the refrigeration cycle.

In contrast, charging in the gas phase would not provide the necessary control or efficiency for the system, while the solid phase and aqueous phase are not relevant to the operation of a typical vapor compression refrigeration system.