What is the purpose of the condenser in a compression refrigeration system?

The purpose of the condenser in a compression refrigeration system is to condense vapor refrigerant into liquid form. In the refrigeration cycle, after the refrigerant has absorbed heat and evaporated in the evaporator, it enters the compressor as a low-pressure vapor. The compressor then increases the pressure and temperature of this vapor before sending it to the condenser.

In the condenser, the high-pressure vapor refrigerant releases its heat to the surrounding environment, typically to the air or water, causing it to cool down. As the refrigerant cools, it undergoes a phase change from vapor to liquid. This process is crucial because it prepares the refrigerant for subsequent cycles where it can again absorb heat in the evaporator.

The other options highlight different functions that are not performed by the condenser. While the refrigerant must evaporate in the evaporator, that function is not part of the condenser's role. Additionally, absorbing heat from surroundings usually occurs in the evaporator, and increasing humidity is not a function associated with either the condenser or the overall refrigeration cycle. The primary and essential role of the condenser is indeed to condense the vapor refrigerant.