What is the state of refrigerant as it enters the compressor in a reciprocating machine?

In a reciprocating compressor, the refrigerant enters in a superheated vapor state. This is the phase where the refrigerant is entirely in vapor form, meaning it has been subjected to enough heat to ensure that it is not only in a gaseous state but also has absorbed additional energy.

Entering in a superheated vapor state is crucial for the efficient operation of the compressor. If the refrigerant were to enter as a liquid or a saturated vapor, there is a risk that liquid could be drawn into the compressor, which could potentially cause damage to the machine or lead to inefficient performance since compressors are designed to compress gases rather than liquids.

Therefore, it is necessary for the refrigerant to be superheated before entering the compressor to maintain operational integrity and efficiency within the refrigeration cycle. This approach ensures that the system can function correctly without risking mechanical failure or loss of performance.