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Unformatted text preview: 49).
The value of hT greatly depends on the design of the individual components
that make up the turbine. Well-designed, large turbines have isentropic efficiencies above 90 percent. For small turbines, however, it may drop even
below 70 percent. The value of the isentropic efficiency of a turbine is determined by measuring the actual work output of the turbine and by calculating
the isentropic work output for the measured inlet conditions and the exit pressure. This value can then be used conveniently in the design of power plants. EXAMPLE 7–14 P1
Inlet state h Isentropic Efficiency of a Steam Turbine Steam enters an adiabatic turbine steadily at 3 MPa and 400°C and leaves at
50 kPa and 100°C. If the power output of the turbine is 2 MW, determine (a)
the isentropic efficiency of the turbine and (b) the mass flow rate of the steam
flowing through the turbine. SOLUTION A sketch of the system and the T-s diagram of the process are given
in Fig. 7–50.
Assumptions 1 Steady operating conditions exist. 2 The changes in kinetic and
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This document was uploaded on 11/28/2012.
- Spring '09