Which of the following are the main components of a refrigeration system?

The main components of a refrigeration system are the compressor, condenser, expansion valve, and evaporator. Each of these elements plays a critical role in the refrigeration cycle, which is essential for the system to remove heat from a designated area.

The compressor is responsible for compressing the refrigerant, raising its pressure and temperature before it enters the condenser. In the condenser, the refrigerant releases heat to the surrounding environment and changes from a gas to a liquid state. The liquid refrigerant then passes through the expansion valve, where its pressure is reduced, leading to a drop in temperature. Finally, in the evaporator, the refrigerant absorbs heat from the surroundings, thus cooling the area. This cycle continues, allowing for efficient refrigeration.

The other options present components that are not part of a standard refrigeration system. For instance, a generator, while important in other processes, does not fit within the refrigeration context outlined. Similarly, components like an engine, turbine, boiler, heater, and thermostat serve entirely different functions in energy systems or HVAC but are not relevant in typical refrigeration applications.