When refrigerant enters the compressor, what is its state?

When refrigerant enters the compressor, it is indeed in a low pressure, low temperature superheated vapor state. This is because the refrigerant leaves the evaporator coil, where it absorbs heat from the interior of the building, causing it to change from a low-pressure liquid to a vapor. During the evaporation process, the refrigerant becomes superheated, meaning its temperature increases above its boiling point at the given pressure without any phase change occurring.

The compressor is designed to take this low pressure superheated vapor and compress it into a high pressure superheated vapor, increasing both its temperature and pressure as it moves to the condenser. The properties of the refrigerant at the point of entering the compressor—as a low pressure and low temperature superheated vapor—are crucial for efficient system operation and heat absorption.