Determine the entropy generated during this process

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Unformatted text preview: 5ºC · →0 ∆Ssystem 123 Rate of net entropy transfer by heat and mass Brick wall Entropy Generation during a Throttling Process Steam at 7 MPa and 450°C is throttled in a valve to a pressure of 3 MPa during a steady-flow process. Determine the entropy generated during this process and check if the increase of entropy principle is satisfied. SOLUTION We take the throttling valve as the system (Fig. 7–66). This is a control volume since mass crosses the system boundary during the process. We · · · note that there is only one inlet and one exit and thus m 1 m 2 m . Also, the FIGURE 7–65 Schematic for Example 7–17. cen54261_ch07.qxd 11/18/03 9:57 AM Page 326 326 FUNDAMENTALS OF THERMAL-FLUID SCIENCES T,°C Throttling process 1 450 P1 = 7 MPa 2 h= con T1 = 450°C st. P2 = 3 MPa FIGURE 7–66 Schematic and T-s diagram for Example 7–18. s1 s2 s enthalpy of a fluid remains nearly constant during a throttling process and thus h2 h1. Assumptions 1 This is a steady-flow process since there is no change with time at any point and thus ∆mCV 0, ∆ECV 0, and ∆SCV 0. 2 Heat transfer to or from the valve is...
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This document was uploaded on 11/28/2012.

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