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Unformatted text preview: ME 326: THERMODYNAMICS I Test 3, Dec. 1, 1995 1) (33%) An inventor brings you a heat engine that she claims takes thermal energy from a solar collector at 227C at a rate of 300 kW, converts 200 kW to mechanical power and rejects the rest to a cooling pond at 27C. a) What is the thermal efficiency of this heat engine if it operates as claimed? b) Does this heat engine violate the first law of thermodynamics? c) Does this heat engine violate the second law of thermodynamics? (Provide some mathematical justification for your answers.) SOLUTION: a) =W net /Q h =200/300=0.67 or 67% b) Write First Law around complete cycle: W net =Q h-Q c or Q c = Q h - W net =300-200 = 100 kW; As long as rejected rate of heat transfer is 100 kW, the device obeys the First Law ....
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