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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
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
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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