Electricity and process heat requirements of a manufacturing facility are to be met by a cogeneration plant consisting of a gas turbine and a heat exchanger for steam production. The plant operates on the simple Brayton cycle between the pressure limits of 100 and 1000 kPa with air as the working fluid. Air enters the compressor at 208C. Combustion gases leave the turbine and enter the heat exchanger at 4508C, and leave the heat exchanger of 3258C, while the liquid water enters the heat exchanger at 158C and leaves at 2008C as a saturated vapor. The net power produced by the gas-turbine cycle is 1500 kW. Assuming a compressor isentropic efficiency of 86 percent and a turbine isentropic efficiency of 88 percent and using variable specific heats, determine
(a) The mass flow rate of air
(b) The back work ratio and the thermal efficiency
(c) The rate at which steam is produced in the heat exchanger. Also determine
(d) The utilization efficiency of the cogeneration plant, defined as the ratio of the total energy utilized to the energy supplied to the plant.

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325°С 15°С Heat exchanger Combustion- 4500 sal. vapor chamber 2 2 MPa 200°C Compressor Turbine 100 kPa 20°C FIGURE P9-171