Refrigeration Cycle Flashcards

What are the four main components of a basic vapour-compression refrigeration cycle?

Answer: Compressor, condenser, expansion valve, evaporator

The four essential components of a vapour-compression refrigeration cycle are: compressor (raises pressure and temperature), condenser (rejects heat), expansion device/metering device (reduces pressure), and evaporator (absorbs heat). Refrigerant flows through these components in a continuous cycle.

In the refrigeration cycle, what state change does the refrigerant undergo in the evaporator?

Answer: Liquid to gas (evaporation/boiling)

In the evaporator, low-pressure liquid refrigerant absorbs heat from the space being cooled and changes state from liquid to gas (evaporation). This phase change absorbs a large amount of latent heat, which is what produces the cooling effect.

What is superheat in the refrigeration cycle and why is it important?

Answer: The temperature above the boiling point of the refrigerant vapour leaving the evaporator; it ensures no liquid enters the compressor

Superheat is the temperature of the refrigerant vapour above its saturation (boiling) temperature at a given pressure. Measuring superheat at the evaporator outlet ensures all liquid has evaporated and only vapour enters the compressor, preventing liquid slugging that can damage the compressor.

What is subcooling in the refrigeration cycle?

Answer: The temperature of the liquid refrigerant below its condensing (saturation) temperature at condenser pressure

Subcooling is the temperature difference between the actual liquid refrigerant temperature and its saturation temperature at condenser pressure. Adequate subcooling (typically 5°C to 10°C) ensures solid liquid reaches the metering device, improving system efficiency and indicating proper refrigerant charge.

What is the relationship between pressure and boiling point of a refrigerant?

Answer: As pressure increases, the boiling point increases; as pressure decreases, the boiling point decreases

The boiling point of a refrigerant is directly related to its pressure. This principle is fundamental to refrigeration: the low-pressure side allows the refrigerant to boil at a low temperature (absorbing heat), while the high-pressure side forces it to condense at a higher temperature (rejecting heat).

What is the coefficient of performance (COP) in a refrigeration system?

Answer: The ratio of cooling capacity (heat removed) to the energy input (work done by compressor)

COP is the ratio of useful cooling output to the work input required to achieve it. A COP of 3 means the system removes 3 units of heat for every 1 unit of electrical energy consumed. Higher COP indicates greater efficiency. COP varies with operating conditions, particularly evaporator and condenser temperatures.