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Water is the working fluid in a cogeneration cycle that generates electricity an

ID: 2995201 • Letter: W

Question

Water is the working fluid in a cogeneration cycle that generates electricity and provides heat for campus buildings. Steam at 2 MPa and 320 C enters a high-pressure turbine with a mass flow rate of 0.82 kg/s. A fraction of the total flow, 0.141 is extracted between the high-pressure and low-pressure turbines at 0.15 MPa to provide for building heating, and the remainder expands through the low-pressure turbine to the condenser pressure at 0.06 bars. Condensate returns from the campus buildings at 0.1 MPa, 60 C and passes through a trap into the condenser, where it is reunited with the main feedwater flow. Each turbine stage has an isentropic efficiency of 80% and the pumping process can be considered isentropic. Determine


(a) the rate of heat transfer to the working fluid passing through the steam generator

(b) the net power developed

(c) the rate of heat transfer for building heating

(d) the rate of heat transfer to the cooling water passing through the condenser

(e) the utilization factor

(f) the thermal efficiency considering the cycle doesn't provide building heating. This means there is no steam being extracted between the high-pressure and low-pressure turbines.

Explanation / Answer

24.4%, (b) 0.62, (c) 1196 kJ/kg, (d) 903 kJ/kg