FTFS Chap08 P176

# FTFS Chap08 P176 - Chapter 8 Power and Refrigeration Cycles...

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Chapter 8 Power and Refrigeration Cycles 8-176 A steam power plant operating on the ideal Rankine cycle with reheating is considered. The reheat pressures of the cycle are to be determined for the cases of single and double reheat. Assumptions 1 Steady operating conditions exist. 2 Kinetic and potential energy changes are negligible. Analysis ( a ) Single Reheat : From the steam tables (Tables A-4, A-5, and A-6),   MPa 5.098 5 6 5 5 6 6 6 6 6 6 C 600 K kJ/kg 250 7 5009 7 88 0 6493 0 kJ/kg 5 2297 8 2392 88 0 83 191 88 0 kPa 10 P s s T . . . . s x s s . . . . h x h h . x P fg f fg f ( b ) Double Reheat : C 600 and K kJ/kg 3602 6 C 600 MPa 25 5 5 3 4 4 3 3 3 T P P s s P P . s T P x x Any pressure P x selected between the limits of 25 MPa and 5.098 MPa will satisfy the requirements, and can be used for the double reheat pressure. 8-164 1 5 2 6 s T 3 4 25 MPa 10 kPa 600 C SINGLE 1 5 2 8 s T 3 4 25 MPa 10 kPa 600 C DOUBLE 7 6

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Chapter 8 Power and Refrigeration Cycles 8-177E A geothermal power plant operating on the simple Rankine cycle using an organic fluid as the working fluid is considered. The exit temperature of the geothermal water from the vaporizer, the rate of heat rejection from the working fluid in the condenser, the mass flow rate of geothermal water at the preheater, and the thermal efficiency of the Level I cycle of this plant are to be determined. Assumptions 1 Steady operating conditions exist. 2 Kinetic and potential energy changes are negligible. Analysis ( a ) The exit temperature of geothermal water from the vaporizer is determined from the steady-flow energy balance on the geothermal water (brine),   F 267.4 2 2 1 2 brine brine F 325 F Btu/lbm 1.03 lbm/h 384,286 Btu/h 000 790 22 T T , , T T C m Q p ( b ) The rate of heat rejection from the working fluid to the air in the condenser is determined from the steady-flow energy balance on air,   MBtu/h 29.7 F 55 5 84 F Btu/lbm 0.24 lbm/h 4,195,100 8 9 air air . T T C m Q p ( c ) The mass flow rate of geothermal water at the preheater is determined from the steady-flow energy balance on the geothermal water,  lbm/h 187,120 geo geo in out geo geo F 8 221 0 154 F Btu/lbm 1.03 Btu/h 000 140 11 m . . m , , T T C m Q p ( d ) The rate of heat input is and , , , , , , Q Q Q W in vaporizer reheater net Btu /h kW 22 790 000 11140 000 33 930 000 1271 200 1071 Then, 10.8% kWh 1 Btu 3412.14 Btu/h 33,930,000 kW 1071 in net Q W th 8-165
Chapter 8 Power and Refrigeration Cycles 8-178 A steam power plant operates on the simple ideal Rankine cycle. The turbine inlet temperature, the net power output, the thermal efficiency, and the minimum mass flow rate of the cooling water required are to be determined.

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