Problem

Other Gas Power System Applications A simple gas turbine is the topping cycle for a simple...

Other Gas Power System Applications A simple gas turbine is the topping cycle for a simple vapor power cycle (Fig. 9.22). Air enters the compressor of the gas turbine at 60°F, 14.7 lbf/in.2, with a volumetric flow rate of 40,000 ft3/min. The compressor pressure ratio is 12 and the turbine inlet temperature is 2600°R. The compressor and turbine each have isentropic efficiencies of 88%. The air leaves the interconnecting heat exchanger at 840°R, 14.7 lbf/ in.2 Steam enters the turbine of the vapor cycle at 1000 lbf/ in.2, 900°F, and expands to the condenser pressure of 1 lbf/in.2 Water enters the pump as saturated liquid at 1 lbf/in.2 The turbine and pump efficiencies are 90 and 70%, respectively. Cooling water passing through the condenser experiences a temperature rise from 60 to 80°F with a negligible change in pressure. Determine

(a) the mass flow rates of the air, steam, and cooling water, each in lb/h.
(b) the net power developed by the gas turbine cycle and the vapor cycle, respectively, each in Btu/h.
(c) the thermal efficiency of the combined cycle.
(d) a full accounting of the net exergy increase of the air passing through the combustor of the gas turbine, mair [ef3 − ef2], in Btu/h. Discuss.

Let T0 = 520°R, p0 = 14.7 lbf/in.2