USCG Third Assistant Engineer (3/AE) Practice Test

The purpose of a compressor in a marine air conditioning system is to compress refrigerant gas for heat exchange. This is a crucial function in the refrigeration cycle, where the compressor increases the pressure and temperature of the refrigerant gas, allowing it to flow through the system.

In the air conditioning context, after the refrigerant has absorbed heat from the indoor air, it enters the compressor in a low-pressure, low-temperature gaseous state. The compressor then compresses this gas, transforming it into a high-pressure, high-temperature gas which subsequently moves to the condenser. In the condenser, the refrigerant releases the absorbed heat and turns back into a liquid state, which then continues through the system to absorb heat again, creating a continuous cycle of cooling.

The other options describe components or functions not directly related to the primary role of a compressor in this system. For instance, filtering air particles is typically accomplished by air filters, and cooling engine oil is usually managed by separate systems such as oil coolers. Regulating fresh air intake pertains to ventilation systems, not the function of a compressor in air conditioning. Thus, option B precisely captures the essential role of the compressor in facilitating the refrigeration cycle, making it the correct choice.