756 for each case with the following results

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Unformatted text preview: ling). Assuming all three processes are executed between the same pressure levels (P1 and P2) in an internally reversible manner and the gas behaves as an ideal gas (Pυ RT) with constant specific heats, we see that the compression work is determined by performing the integration in Eq. 7–56 for each case, with the following results: cen54261_ch07.qxd 11/18/03 9:57 AM Page 309 309 CHAPTER 7 Isentropic (Pυ k constant): wcomp, in Polytropic (Pυ n kRT1 k1 P2 P1 (k 1)/k nRT1 n1 P2 P1 (n 1)/n 1 (7–57a) 1 (7–57b) constant): wcomp, in Isothermal (Pυ kR(T2 T1) k1 nR(T2 T1) n1 constant): wcomp, in RT ln P2 P1 (7–57c) The three processes are plotted on a P-υ diagram in Fig. 7–45 for the same inlet state and exit pressure. On a P-υ diagram, the area to the left of the process curve is the integral of υ dP. Thus it is a measure of the steady-flow compression work. It is interesting to observe from this diagram that of the three internally reversible cases considered, the adiabatic compression (Pυ k constant) requires the maximum work...
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