1. Two pounds of air initially at 200°F and 50 lbf/in.2 undergo two processes in series:
Process 1-2: Isothermal to p2 5 10 lbf/in.2
Process 2-3: Constant pressure to T3 5 210°F Employing the ideal gas model
(a) represent each process on a p-y diagram and indicate the dead state.
(b) determine the change in exergy for each process, in Btu.
Let T0 5 77°F, p0 5 14.7 lbf/in.2 and ignore the effects of motion and gravity.
2. Twenty pounds of air initially at 1560°R, 3 atm fills a rigid tank. The air is cooled to 1040°R, 2 atm. For the air modeled as an ideal gas
(a) indicate the initial state, final state, and dead state on a T-y diagram.
(b) determine the heat transfer, in Btu.
(c) determine the change in exergy, in Btu, and interpret the sign using the T-y diagram of part (a).
Let T0 5 520°R, p0 5 1 atm and ignore the effects of motion and gravity.