Regenerative Air Cooling System

The regenerative air cooling-system is a modification of a simple air cooling system with the addition of a regenerative heat exchanger. The high pressure and high temperature air from the main compressor is first cooled by the ram air in the heat exchanger. This air is further cooled in the regenerative heat exchanger with a portion of the air bled after expansion in the cooling turbine.

This type of cooling system is used for supersonic aircrafts and rockets.

 The T-s diagram for the regenerative air cooling system is shown above. The various processes are as follows:

1. The process 1-2 represents' isentropic ramming of air and process 1-2' represents actual ramming of air because of internal friction due to irreversibilities. 2. The process 2'-3 represents isentropic compression of air in the main compressor and the process 2'-3' represents actual compression of air because of internal friction due to irreversibilities. 3. The process 3'-4 represents cooling of compressed air by ram air in the heat exchanger. 4. The process 4-5 represents cooling of air in the regenerative heat exchanger. 5. The process 5-6 represents isentropic expansion of air in the cooling turbine up to the cabin pressure and the process 5-6' represents actual expansion of air in the cooling turbine. 6.The process 6'-7 represents heating of air upto the cabin temperature T7.

If Q tonnes of refrigeration is the cooling load in the cabin, then the quantity of air required for the refrigeration purpose will be

For the energy balance of regenerative heat exchanger, we have

Where T8 = Temperature of air leaving to atmosphere from the regenerative heat exchanger

Power required for the refrigeration system:

and C.O.P. of the refrigerating system: