• This system is similar to simple air cooling system except that the rammed air cannot be directly used as a coolant in the heat exchanger. This is because Reduced ambient system is employed for very high speed aircrafts eg. Supersonic aircrafts and rockets. Hence the temperature of rammed air would be very high.
• So we first expand the rammed air in the turbine to decrease its temperature.
• Power developed by both turbines is used to run the fan which ensures sufficient amount of airflow over the heat exchanger tubes.

Fig. Reduced Ambient 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