Unformatted text preview: entropic relation is obtained
in a similar manner from Eq. 7–34 with the following result:
T2
T1 s const. P2
P1 (k 1)/k (ideal gas) (7–43) The third isentropic relation is obtained by substituting Eq. 7–43 into
Eq. 7–42 and simplifying:
P2
P1 s const. υ1
υ2 k (ideal gas) (7–44) Equations 7–42 through 7–44 can also be expressed in a compact form as
Tυ k 1
TP(1 k)/k
Pυ k ((
T2
T1 s = const. = (k –1)/k ((
P2
P1 = υ1
υ2 k –1 (( *ideal gas
VALID FOR *isentropic process
*constant specific heats constant
constant
constant (7–45) (ideal gas) (7–46)
(7–47) The specific heat ratio k, in general, varies with temperature, and thus an
average k value for the given temperature range should be used.
Note that the idealgas isentropic relations above, as the name implies, are
strictly valid for isentropic processes only when the constantspecificheat
assumption is appropriate (Fig. 7–36). Variable Specific Heats (Exact Analysis)
FIGURE 7–36
The isentropic relations of ideal gases
are valid for the isentropic processes
of ideal gases...
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This document was uploaded on 11/28/2012.
 Spring '09

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