(Source: Natural Resources Canada's Booklet Air Conditioning Your Home)
Reproduced with the Her Majesty the Queen in Right of Canada, 2001

Compressor

(Source: http://web.mit.edu/2.972/...)

Thermodynamics of Process	Increase the pressure of a gas through the input of shaft work
Mechanics of Process	Increases the temperature of a gas Increases the pressure of a gas by physically decreasing the volume
Energy Balance
Entropy Balance	or
Assumptions (for calculations)	Steady state Adiabatic Reversible

Condenser

Thermodynamics of Process	Phase change from a vapor to a liquid releasing the latent heat
Mechanics of Process	Similar to a heat exchanger Flows through coils with fins to enhance heat transfer
Energy Balance
Entropy Balance	or
Assumptions (for calculations)	Steady state Reversible

Expansion Valve

Thermodynamics of Process	Reduces the pressure of the vapor without any shaft work or acceleration of the vapor
Mechanics of Process	Reduces the pressure of the fluid at constant temperature
Energy Balance
Entropy Balance
Assumptions (for calculations)	Steady state Adiabatic Irreversible

Evaporator

Thermodynamics of Process	Evaporates the liquid to a low pressure vapor
Mechanics of Process	Similar to a heat exchanger Flows through coils with fins to enhance heat transfer
Energy Balance
Entropy Balance	or
Assumptions (for calculations)	Steady state Reversible