Understanding Heat Rejection in the VCR Cycle

The Vapour Compression Refrigeration (VCR) cycle is a widely used method for refrigeration and air conditioning. It involves four main components: the evaporator, the compressor, the condenser, and the expansion valve.

Components and Their Functions in the VCR Cycle

Let's briefly look at what happens in each part of the cycle:

• Evaporator: This is where the low-pressure, low-temperature liquid refrigerant absorbs heat from the space being cooled. As it absorbs heat, it boils and turns into a low-pressure vapor. This is where heat is absorbed.
• Compressor: The compressor takes the low-pressure refrigerant vapor from the evaporator and compresses it into a high-pressure, high-temperature vapor. This process requires work input.
• Condenser: The high-pressure, high-temperature refrigerant vapor flows into the condenser. Here, it comes into contact with a cooler medium (like air or water). The refrigerant loses heat to this cooler medium, causing it to condense back into a high-pressure liquid. This is where heat is rejected to the surroundings.
• Expansion Valve (or Throttle Valve): The high-pressure liquid refrigerant from the condenser passes through the expansion valve. This valve reduces the pressure and temperature of the refrigerant before it enters the evaporator. It does not involve heat transfer.

Where Heat is Rejected in the VCR Cycle

Based on the functions of the components, the refrigerant releases or rejects heat in the condenser. The purpose of the condenser is specifically to transfer the heat picked up in the evaporator (plus the heat equivalent of the work done by the compressor) to the outside environment or a heat sink.

Therefore, in the VCR based refrigerant cycle, the refrigerant rejects heat at the condenser.