Which part of a heat exchanger changes the state of the refrigerant to 100% liquid?

The part of a heat exchanger that changes the state of the refrigerant to 100% liquid is the condenser. In a refrigeration cycle, the condenser operates by rejecting heat from the refrigerant, which has been vaporized in the evaporator. As the vapor passes through the condenser, it releases heat to the surrounding environment, leading to a phase change from vapor to liquid.

This process is critical as it allows the refrigerant to condense completely into a liquid state before it enters the expansion device. The effectiveness of the condenser directly influences the system's efficiency, as proper condensation ensures that the refrigerant is in the correct state to continue the cycle and efficiently transfer heat in the next stages.

The expansion device, on the other hand, is responsible for reducing the pressure of the liquid refrigerant, causing it to evaporate; the compressor increases the pressure and temperature of the refrigerant vapor; while the evaporator is where the liquid refrigerant absorbs heat and evaporates into gas. Thus, it is the condenser that specifically performs the function of transitioning the refrigerant to a 100% liquid state.