Which of the following is NOT a main component of a refrigeration system?

In a refrigeration system, the main components typically include the compressor, expansion valve, and evaporator. Each of these components plays a critical role in the refrigeration cycle.

The compressor is responsible for circulating refrigerant through the system, compressing it to increase its pressure and temperature. The expansion valve then allows the high-pressure refrigerant to expand, lowering its pressure and temperature, which is essential for cooling. The evaporator is where the refrigerant absorbs heat from the environment, allowing it to cool the air or the space being refrigerated.

The heater, on the other hand, is not a component found in a standard refrigeration system. While heating elements may be utilized in certain applications, they do not form part of the fundamental operation of a refrigeration cycle, which aims to remove heat rather than add it. Hence, the heater is correctly identified as not being a main component of a refrigeration system.