Evaporator function: After the expansion valve, the evaporator converts the low-pressure refrigerant into which state as it absorbs heat from the space?

Introduction / Context:
The evaporator is the cooling coil of a vapour-compression system. It is where the refrigerant absorbs heat from the conditioned space and changes phase from liquid to vapour at low pressure.

Given Data / Assumptions:

• Refrigerant exits the expansion device as a low-pressure, low-temperature mixture.
• Heat is absorbed from air or a secondary fluid flowing over/through the coil.
• Proper superheat is maintained at the outlet to protect the compressor.

Concept / Approach:
Boiling at nearly constant pressure in the evaporator removes heat from the medium. By the outlet, the design goal is dry saturated or slightly superheated vapour to ensure no liquid enters the compressor.

Step-by-Step Solution:

Verification / Alternative check:
Pressure–enthalpy plotting shows a horizontal (constant-pressure) path across the saturated dome from mixture to saturated vapour, then a slight superheat rise.

Why Other Options Are Wrong:

• High-pressure liquid does not occur in the evaporator; it is a low-pressure component.
• While the inlet is a mixture, the question asks for the state produced by the evaporator (outlet), which is vapour.
• High-pressure superheated vapour is a compressor discharge condition, not evaporator outlet.

Common Pitfalls:
Confusing inlet (mixture) and outlet (vapour) states; overlooking the need for slight superheat as a control target.

Final Answer:
Low-pressure vapour refrigerant (at outlet, after complete evaporation)