Helium gas is compressed from 16 psia and 85°F to 120 psia at a rate of 10 ft3/s. Determine the power input to the compressor, assuming the compression process to be 
(a) isentropic
(b) polytropic with n = 1.2
(c) isothermal
(d) ideal two-stage polytropic with n = 1.2.

Solution