A binary geothermal power plant uses geothermal water at 160°Cas the heat source. The plant operates on the simple Rankine cyclewith isobutane as the working fluid. Heat is transferred to thecycle by a heat exchanger in which geothermal liquid water entersat 160°C at a rate of 555.9 kg/s and leaves at 90°C. Isobutaneenters the turbine at 3.25 MPa and 147°C and leaves at 79.5°C and410 kPa. Isobutane is condensed in an air-cooled condenser andpumped to the heat exchanger pressure. Assume that the pump to hasan isentropic efficiency of 90 percent. Take the specific heat ofgeothermal water is taken to be 4.258 kJ/kg·C. The properties ofisobutane are given as h1 = 273.01 kJ/kg, v1 = 0.001842 m3/kg, h3 =761.54 kJ/kg, h4 = 689.74 kJ/kg, and h4s = 670.40 kJ/kg. (a) theisentropic efficiency of the turbine, (b) the net power output ofthe plant, and (c) the thermal efficiency of the cycle.
