Chapter 7

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Unformatted text preview: the facility pays $0.075/kWh for electricity. SOLUTION We take the turbine as the system (Fig. 7–30). This is a control volume since mass crosses the system boundary during the process. We note that · · · there is only one inlet and one exit and thus m 1 m 2 m . Assumptions 1 This is a steady-flow process since there is no change with time at any point and thus mCV 0, ECV 0, and SCV 0. 2 The turbine is adiabatic and thus there is no heat transfer. 3 The process is reversible. 4 Kinetic and potential energies are negligible. Analysis The assumptions above are reasonable since a turbine is normally well-insulated and it must involve no irreversibilities for best performance and thus maximum power production. Therefore, the process through the turbine must be reversible adiabatic or isentropic. Then, s2 s1 and State 1: P1 T1 5 MPa 115 K State 2: P2 s2 1 MPa s1 h1 s1 1 h2 232.2 kJ/kg 4.9945 kJ/kg · K 422.15 kg/s 222.8 kJ/kg Also, the mass flow rate of liquid methane is · m · r1V 1 (422.15 kg...
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This document was uploaded on 11/28/2012.

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