A regenerative air refrigeration system for an aeroplane is designed to take a load of 25 TR. The temperature and pressure Conditions for atmosphere are 5$^{\circ}$C and 0.85 bar.

The temperature and pressure of air is increased from 0.85 bar and 1.2 bar due ramming action. The pressure of leaving the main Compresssor is 4.8 bar. 60% of total heat of air leaving the main compressor is removed in heat exchanger and then passed through the cooling turbine. The temperature of rammed air which is used for cooling purpose in the heat exchanger is reduced to 50˚C by mixing the air coming out from the cooling turbine. The isentropic Efficiencies of Compressor and turbine are 90% and 80% respectively. Assuming isentropic ramming and mass of cooled air passing through heat exchanger equal to mass of cooling air, Find Ratio of by passed air to ram air used for cooling purpose and (ii) the power required for maintaining the cabin at required condition.

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