As mentioned earlier mass possesses entropy as well

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Unformatted text preview: The entropy balance relations for control volumes differ from those for closed systems in that they involve one more mechanism of entropy exchange: mass flow across the boundaries. As mentioned earlier, mass possesses entropy as well as energy, and the amounts of these two extensive properties are proportional to the amount of mass (Fig. 7–63). { System FIGURE 7–63 The entropy of a control volume changes as a result of mass flow as well as heat transfer. cen54261_ch07.qxd 11/18/03 9:57 AM Page 324 324 FUNDAMENTALS OF THERMAL-FLUID SCIENCES Taking the positive direction of heat transfer to be to the system, the general entropy balance relations (Eqs. 7–76 and 7–77) can be expressed for control volumes as Qk Tk misi mese Sgen (S2 S1)CV (kJ/K) (7–82) or, in the rate form, as · Qk Tk · m isi · m ese · Sgen · ∆SCV (kW/K) (7–83) This entropy balance relation can be stated as: the rate of entropy change within the control volume during a process is equal to the sum of the rate of entropy transfer through the control volume boundary by heat trans...
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