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Unformatted text preview: he denominator. This is because ws
is a smaller quantity than wa, and this definition prevents hC from becoming
greater than 100 percent, which would falsely imply that the actual compressors performed better than the isentropic ones. Also notice that the inlet conditions and the exit pressure of the gas are the same for both the actual and the
When the changes in kinetic and potential energies of the gas being compressed are negligible, the work input to an adiabatic compressor becomes
equal to the change in enthalpy, and Eq. 7–62 for this case becomes
h2a hC ws
wa υ (P2
h2a (7–63) P1)
wa P2 h2a
process 2s h2s
process ws h1 1 Inlet
state s2s = s1 s FIGURE 7–51
The h-s diagram of the actual and
isentropic processes of an
adiabatic compressor. (7–64) When no attempt is made to cool the gas as it is compressed, the actual
compression process is nearly adiabatic and the reversible adiabatic (i.e., isentropic) process serves well as the ideal process. However, sometimes compressors are cooled intentionally by utilizing fins or a water jacket placed
around the casing to red...
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This document was uploaded on 11/28/2012.
- Spring '09