In a DX or dry expansion evaporator, in what condition should the refrigerant leave?

In a DX (direct expansion) evaporator, it is crucial for the refrigerant to leave in a superheated state. This means that the refrigerant has absorbed sufficient heat and is fully vaporized, ensuring it is in a gaseous state above its saturation temperature.

Leaving the evaporator as superheated vapor is important because it prevents any liquid refrigerant from entering the compressor. If liquid refrigerant were to enter the compressor, it could cause damage through a phenomenon known as liquid slugging, which can severely compromise the compressor's efficiency and longevity. By being superheated, the refrigerant is entirely in the vapor phase, allowing for efficient compression and circulation through the system.

In contrast, if the refrigerant were to leave as saturated or subcooled, it could either carry liquid into the compressor or be too cool and dense to optimize the compression process. Therefore, ensuring that the refrigerant exits the evaporator as superheated vapor is essential for the operational efficiency of the cooling system.