# Assign8-2 - Problem Statement 24 Consider a Carnot cycle...

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Problem Statement: 24 Consider a Carnot cycle executed in a closed system with air as the working fluid. The maximum pressure in the cycle is 800.000 kPa while the maximum temperature is 750.00 K. If the entropy increase during the isothermal heat rejection process is 0.25 kJ/kg*K and the net work output is 100.00 kJ/kg, determine: a) the minimum pressure in the cycle b) the heat rejection from the cycle c) the thermal efficiency of the cycle d) If an actual heat engine cycle operates between the same temperature limits and produ 5200.000 kW of power for an air flow rate of 90.00 kg/s, determine the 2nd law efficiency of this cycle. Schematic: Assumptions/Approximations: Air is an ideal gas with constant specific heats Physical Laws: Properties/Sources: 0.29 kJ/kg*K [Table A-2] 0.718 kJ/kg*K [Table A-2] 1.005 kJ/kg*K [Table A-2] 1.400 Calculation: 350.00 K 55.467 kPa [Book answer is in error] 3.14 23.21 kPa 87.50 kJ/kg 9000.00 kW 53.33% w NET = (s 2 - s 1 )*(T H - T L ) s 12 = - s 34 = Cp AIR *ln(T 4 /T 3 ) - R AIR *(ln(P 4 ) - ln(P 3 )) η th = 1 - T L /T H P 1 = P 4 *(T 1 /T 4 ) (k/(k - 1)) q OUT = T L * s 12 η II = W ACTUAL /W CARNOT R AIR = Cv AIR = Cp AIR = k = Cp AIR /Cv AIR = w NET = (s 2 - s 1 )*(T H - T L ) ==> T L = T 4 = P 1 = P 4 *(T 1 /T 4 ) (k/(k - 1)) ==> P 4 = s 12 = - s 34 = Cp AIR *ln(T 4 /T 3 ) - R AIR *(ln(P 4 ) - ln(P 3 )) ==> ln(P 3 ) P 3 = q OUT = T L * s 12 = CARNOT = *w

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Assign8-2 - Problem Statement 24 Consider a Carnot cycle...

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