What type of refrigerant mixture enters a direct expansion (DX) evaporator?

A direct expansion (DX) evaporator operates by utilizing a refrigerant mixture that consists of liquid refrigerant and a certain amount of vapor that is produced as the refrigerant absorbs heat. In this evaporator, as the refrigerant enters, it undergoes a phase change; part of it evaporates while part remains in liquid form. The presence of both liquid and vapor is essential because the liquid refrigerant absorbs heat from the surrounding environment, causing it to evaporate and convert into a vapor.

This mixture, containing both liquid and vapor, allows the system to efficiently absorb heat, enhancing the overall cooling performance of the refrigeration cycle. The goal is to optimize the heat transfer process, which is why this mixture of liquid with some flash gas is the correct choice, ensuring that the refrigerant fully utilizes its heat absorption capabilities before exiting the evaporator.