Question

An expansion in a gas turbine can be approximated with a polytropic process with exponent n = 1.25. The inlet air is at 2100 R, 120 psia and the exit pressure is 18 psia with a mass flow rate of 2 lbm/s. Find the turbine heat transfer and power output. 

Answer 1

C.V. Steady state device, single inlet and single exit flow.

Notice: dP < 0 so dw > 0

ds > 0 so dq > 0

Notice this process has some heat transfer in during expansion which is unusual. The typical process would have n = 1.5 with a heat loss.