An air standard cycle with a variable specific heats is executed in a closed system and is composed of the following four processes: (1) 1-2: Isentropic compression from 95 kPa and 25oC to 900 kPa, (2) 2-3: v = constant during heat addition to 1200oC, (3) 3-4: Isentropic expansions to 95 kPa, (4) 4-1: p = constant during heat rejection to initial state.
(a) Calculate the net work (wnet) output per unit mass and
(b) Determine the thermal efficiency (ηth). Use the IG model for air.