Mumbai University > Mechanical Engineering > Sem8 > Refrigeration and Air Conditioning

Marks: 5M

Year: Dec 2013

Aircraft air refrigeration systems are required due to heat transfer from many external and internal heat sources (like solar radiation and avionics) which increase the cabin air temperature. With the technological developments in high-speed passenger and jet aircrafts, the air refrigeration systems are proving to be most efficient, compact and simple. Various types of aircraft air refrigeration systems used these days are:

1. Simple air cooling system
2. Simple air evaporative cooling system
3. Boot strap air cooling system
4. Boot strap air evaporative cooling system
5. Reduced ambient air cooling system
6. Regenerative air cooling system.

Simple air cooling system:

Process 1-2= Isentropic ramming of air

Process 2-3i=Isentropic compression in main compressor

Process 2-3=Actual compression in main compressor

Process 3-4=Constant pressure heat rejection in heat exchanger

Process 4-5i=Isentropic expansion in cooling turbine

Process 4-5= Actual expansion in cooling turbine

Process 5-6=Constant pressure heat addition in cabin

• Ambient air gets rammed before the main compressor. The air required for refrigeration system is then bled off from this compressor.
• It is then sent to the heat exchanger where this high pressure and high temperature air is cooled using ram air.
• Air is further cooled in the cooling turbine due to its expansion. The turbine work drives the cooling fan which draws ram air through the heat exchanger.
• The cooled air from turbine is then sent to the aircraft cabin.