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Unformatted text preview: uce the work input requirements (Fig. 7–52). In this
case, the isentropic process is not suitable as the model process since the
device is no longer adiabatic and the isentropic compressor efficiency defined
above is meaningless. A realistic model process for compressors that are intentionally cooled during the compression process is the reversible isothermal
process. Then we can conveniently define an isothermal efficiency for such
cases by comparing the actual process to a reversible isothermal one:
hC 2a it
pr P1 h1
h1 where h2a and h2s are the enthalpy values at the exit state for actual and
isentropic compression processes, respectively, as illustrated in Fig. 7–51.
Again, the value of hC greatly depends on the design of the compressor. Welldesigned compressors have isentropic efficiencies that range from 75 to
When the changes in potential and kinetic energies of a liquid are negligible, the isentropic efficiency of a pump is defined similarly as
hP h (7–65) where wt and w...
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- Spring '09