What is the purpose of a crankcase heater in a refrigeration system?

The purpose of a crankcase heater in a refrigeration system is primarily to prevent refrigerant from migrating into the compressor's crankcase when the system is off. When the compressor is not operational, refrigerant can condense in the crankcase, which can lead to issues such as dilution of the oil, and can cause the compressor to fail during start-up due to difficulties in pumping oil mixed with liquid refrigerant.

A crankcase heater warms the refrigerant in the crankcase sufficiently to keep it in a vapor state. This ensures that there is less chance of liquid refrigerant entering the compressor during the start-up process, which is critical for maintaining the longevity and efficiency of the compressor. This function is vital in preventing compressor damage and ensures reliable operation of the refrigeration system.

The other options, while related to different aspects of refrigeration, do not accurately describe the specific function of the crankcase heater. The increase of refrigerant pressure is related to the overall system design and operation but is not a direct function of the crankcase heater. Cooling the compressor and enhancing heat transfer are also important functions within refrigeration systems but are not roles served by the crankcase heater.