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Q1. A mass of 1.2 kg of air at a pressure and temperature of 1 bar and 20℃ respectively, is compressed isothermally through a volume ratio of 12 :1. It is the n compressed isentropically to a pressure of 48 bar.

The two processes can be replaced by a single polytropic process operating between the same initial and final conditions.

(a) Sketch The processes on pressure-Volume and Temperature entropy diagrams. (2)

(b) Calculate EACH of the following:

(i) The original total work transfer; (5)

(ii) The polytropic work transfer; (5)

(iii) The increase in heat transfer when the polytropic process is used. (4)

Note: for air 1.4, R = 0.287 kJ/ kg K and c_V = 0.718 kJ/kg K.