Cen54261ch07qxd 111803 957 am page 282 282

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Unformatted text preview: other properties). cen54261_ch07.qxd 11/18/03 9:57 AM Page 282 282 FUNDAMENTALS OF THERMAL-FLUID SCIENCES obtained directly from the tables at the specified state. In the saturated mixture region, it is determined from s sf xsfg (kJ/kg · K) where x is the quality and sf and sfg values are listed in the saturation tables. In the absence of compressed liquid data, the entropy of the compressed liquid can be approximated by the entropy of the saturated liquid at the given temperature: s @ T, P sf @ T (kJ/kg · K) The entropy change of a specified mass m (such as a closed system) during a process is simply S ms m(s2 s1) (kJ/K) (7–12) which is the difference between the entropy values at the final and initial states. When studying the second-law aspects of processes, entropy is commonly used as a coordinate on diagrams such as the T-s and h-s diagrams. The general characteristics of the T-s diagram of pure substances are shown in Fig. 7–11 using data for water. Notice from this diagram that the constantvolume lines are steeper than the constant-pressure lines and the constantpressure lines are parallel to the constant-temperature lines in the saturated liquid–vapor mix...
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This document was uploaded on 11/28/2012.

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