A binary geothermal power plant uses geothermal water at 160°C as the heat source. The cycle operates on the simple Rankine cycle with isobutane as the working fluid. Heat is transferred to the cycle by a heat exchanger in which geothermal liquid water enters at 160°C at a rate of 555.9 kg/s and leaves at 90°C. Isobutane enters the turbine at 3.25 MPa and 147°C at a rate of 305.6 kg/s, and leaves at 79.5°C and 410 kPa. Isobutane is condensed in an air-cooled condenser and pumped to the heat exchanger pressure. Assuming the pump to have an isentropic efficiency of 90 percent, determine
(a) The isentropic efficiency of the turbine,
(b) The net power output of the plant, and
(c) The thermal efficiency of the cycle. The properties of isobutane may be obtained from EES.

Isobutane turbine Air-cooled condenser Heat exchanger Pump l1 Geothermal water in Geothermal water out FIGURE P10-25