Aux 2 Unit 8 Refrigeration General overview Q4 Answer
Describe, with the aid of a sketch, the operation of the FOUR main components in a simple vapour compression cycle for a refrigeration system.(10)
FOUR Main Components of a Simple Vapour Compression Cycle and Their Operation
Compressor (2.5 marks)
Operation: The compressor draws in low-pressure, low-temperature refrigerant vapour from the evaporator. It compresses it to a high-pressure, high-temperature vapour.
Purpose: To raise the refrigerant pressure above the condenser pressure, enabling heat rejection to the cooling medium (air or water).
Effect on refrigerant: Low-pressure vapour → High-pressure, high-temperature vapour.
Condenser (2.5 marks)
Operation: The hot, high-pressure vapour enters the condenser, where heat is removed by seawater or air.
Purpose: To reject heat absorbed in the evaporator plus the heat of compression to the surroundings.
Effect on refrigerant: High-pressure vapour → High-pressure liquid (condensation).
Expansion Valve / Throttle Valve (2.5 marks)
Operation: The high-pressure liquid refrigerant passes through the expansion valve or capillary tube, where its pressure suddenly drops.
Purpose: To regulate flow into the evaporator and provide a pressure difference between condenser and evaporator.
Effect on refrigerant: High-pressure liquid → Low-pressure mixture of liquid and vapour (flash gas).
Evaporator (2.5 marks)
Operation: The low-pressure refrigerant absorbs heat from the refrigerated space or cargo.
Purpose: To remove heat from the load and provide cooling effect.
Effect on refrigerant: Low-pressure liquid/vapour mixture → Completely evaporated low-pressure vapour, which returns to the compressor.
