Helium is used in a combined cycle power plant as the working fluid in a simple closed gas turbine serving as the topping cycle for a vapor power cycle. A nuclear reactor is the source of energy input to the helium. The figure below provides steady-state operating data. Helium enters the compressor of the gas turbine at 200 psi, 180°F with a mass flow rate of 8x105lbm/hr and is compressed to 800 psi. The isentropic efficiency of the compressor is 80%. The helium then passes through the reactor with a negligible decrease in pressure, exiting at 1400°F. Next the helium expands through the interconnecting heat exchanger. A separate stream of liquid water enters the heat exchanger and exits as saturated vapor at 1200 psi. The vapor is superheated before entering the turbine at 800°F, 1200 psi. The steam expands through the turbine to 1 psi and a quality of 0.9. Saturated liquid exits the condenser at 1 psi. Cooling water passing through the condenser experiences a temperature rise from 60°F to 90°F. The isentropic pump efficiency is 100%. Stray heat transfer and kinetic and potential energy effects can be nelected. Determine:
(a) The mass flow rates of the steam and cooling water, each in lbm/hr.
(b) The net power developed by the gas turbine and the vapor power cycles, in Btu/hr.
(c) The thermal efficiency of the combined cycle.
