Explanation Write an expression for the mass balance for a tank which acts as a system. m in − m out = Δ m system m i = m 2 (I) Here, mass of air entering to the supply line is m in ( m i ) , the mass of air leaving the system is m o u t , change in mass of a system is Δ m system , and final mass is m out ( m 2 ) . Write an expression for an energy balance for a system. E in − E out = Δ E system m i h i − Q o u t = m 2 u 2 Q o u t = m i h i − m 2 u 2 (II) Here, energy transfer at inlet and outlet condition is E in and E out respectively, and change in energy transfer of a system is Δ E system , enthalpy at initial state is h i , and internal energy at state 2 is u 2 . Equate the equation (I) and (II) Q o u t = m 2 ( h i − u 2 ) = m 2 ( c P T i − c v T i ) = m 2 T i ( c P − c v ) Q o u t = m 2 T i R (III) Write the formula for the final mass of the tank. m 2 = P V R T 2 (IV) Express the exergy destroyed during the process. S in − S out + S gen = Δ S system m i s i − Q o u t T 0 + S gen = m 2 s 2 S gen = ( m 2 s 2 − m i s i ) + Q o u t T 0 S gen = m 2 ( s 2 − s i ) + Q o u t T 0 (V) Here, net entropy transfer by heat and mass is S in − S out , entropy generation is S gen and change in entropy of system is Δ S system . The exergy destroyed in this process is equal to the work potential associated with this process W r e v = X d e s t r o y e d W r e v = T 0 S gen W r e v = T 0 ( m 2 ( s 2 − s i ) + Q o u t T 0 ) (VI) Both states have same temperature and pressure so the change in entropy is zero

8th Edition

ISBN: 9780100257054

Author: CENGEL

Publisher: YUZU

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Chapter 8.8, Problem 68P

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The work potential associated with this process.

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EBK THERMODYNAMICS: AN ENGINEERING APPR

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