It represents a loss since this rise in temperature

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Unformatted text preview: → T2a hN T2a) T2s) or 0.92 764 K That is, the temperature will be 16 K higher at the exit of the actual nozzle as a result of irreversibilities such as friction. It represents a loss since this rise in temperature comes at the expense of kinetic energy (Fig. 7–56). Actual nozzle 950 K AIR Isentropic nozzle 764 K, 639 m/s 748 K, 666 m/s (c) The actual exit velocity of air can be determined from the definition of isentropic efficiency of a nozzle, hN 7–13 I 2 2a 2 2s → 2a N 2 2s FIGURE 7–56 A substance leaves actual nozzles at a higher temperature (thus a lower velocity) as a result of friction. 639 m/s ENTROPY BALANCE The property entropy is a measure of molecular disorder or randomness of a system, and the second law of thermodynamics states that entropy can be created but it cannot be destroyed. Therefore, the entropy change of a system during a process is greater than the entropy transfer by an amount equal to the entropy generated during the process within the system, and the increase of entropy principle for any system is expressed as (Fig. 7–57) Total entropy entering Total entropy leaving Total entropy generated Change in...
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