Refrigeration and air-conditioning

Refrigeration

The process of removing heat from a substance or space to lower its temperature below the ambient temperature.

Air Conditioning

The process of controlling the temperature, humidity, purity, and movement of air in an enclosed space to provide comfort or for industrial processes.

Refrigerant

A working fluid used in refrigeration and air conditioning systems that undergoes phase changes to absorb and release heat.

Coefficient of Performance (COP)

A ratio of the desired output (cooling effect or heating effect) to the required input (work or heat).

Vapor Compression Cycle

A thermodynamic cycle that uses a refrigerant to transfer heat, typically involving compression, condensation, expansion, and evaporation.

Coefficient of Performance (Refrigeration)

Q_L is the heat absorbed from the cold space, W_in is the work input to the compressor.

COP_R = \frac{Q_L}{W_in}

Coefficient of Performance (Heat Pump)

Q_H is the heat rejected to the hot space.

COP_HP = \frac{Q_H}{W_in}

Relationship between COP_R and COP_HP

For the same cycle and work input.

COP_HP = COP_R + 1

Heat Rejected in Condenser

Based on the first law of thermodynamics for the cycle.

Q_H = Q_L + W_in

Ideal Vapor Compression Cycle COP (Carnot)

T_L and T_H are absolute temperatures of the cold and hot reservoirs, respectively. This is for an ideal reversible cycle.

COP_R = \frac{T_L}{T_H - T_L}