754 isentropic efficiencies of nozzles are typically

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Unformatted text preview: lpies as hN h1 h1 h2a h2s Isentropic process 2 2s 2 P2 Exit e ur press 2s 2a (7–67) where h2a and h2s are the enthalpy values at the nozzle exit for the actual and isentropic processes, respectively (Fig. 7–54). Isentropic efficiencies of nozzles are typically above 90 percent, and nozzle efficiencies above 95 percent are not uncommon. EXAMPLE 7–16 2 h2a h2 s Actual process 1 h1 2 P1 Inlet state Effect of Efficiency on Nozzle Exit Velocity Air at 200 kPa and 950 K enters an adiabatic nozzle at low velocity and is discharged at a pressure of 80 kPa. If the isentropic efficiency of the nozzle is 92 percent, determine (a) the maximum possible exit velocity, (b) the exit temperature, and (c) the actual velocity of the air. Assume constant specific heats for air. s2s = s1 s FIGURE 7–54 The h-s diagram of the actual and isentropic processes of an adiabatic nozzle. cen54261_ch07.qxd 11/18/03 9:57 AM Page 318 318 FUNDAMENTALS OF THERMAL-FLUID SCIENCES T, K 1 950 P1 = 200 kPa T1 = 950 K 1 << 2 Pa 0k 20 Actual process Isentropic process AIR NOZZLE ηN...
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This document was uploaded on 11/28/2012.

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