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Unformatted text preview: he dependence of Cυ and Cp on temperature is known. Even
when the Cυ(T) and Cp(T) functions are available, performing long integrations every time entropy change is calculated is not practical. Then two reasonable choices are left: either perform these integrations by simply assuming
constant specific heats or evaluate those integrals once and tabulate the results. Both approaches are presented next. Constant Specific Heats (Approximate Analysis)
Assuming constant specific heats for ideal gases is a common approximation,
and we used this assumption before on several occasions. It usually simplifies
the analysis greatly, and the price we pay for this convenience is some loss in
accuracy. The magnitude of the error introduced by this assumption depends
on the situation at hand. For example, for monatomic ideal gases such as
helium, the specific heats are independent of temperature, and therefore the
constant-specific-heat assumption introduces no error. For ideal gases whose
specific heats vary almost linearly in the temperature range of interest, the
possible error is minimized by using specific h...
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This document was uploaded on 11/28/2012.
- Spring '09