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Unformatted text preview: 1 ME 113: THERMODYNAMICS Spring 2008 Ch 6 HW Solution 2 6-21 The heat rejection and thermal efficiency of a heat engine are given. The heat input to the engine is to be determined. Assumptions 1 The plant operates steadily. 2 Heat losses from the working fluid at the pipes and other components are negligible. Analysis According to the definition of the thermal efficiency as applied to the heat engine, H L H H q q q q w th th net = = which when rearranged gives kJ/kg 1667 = = = 4 . 1 kJ/kg 1000 1 th L H q q 6-43 The cooling effect and the COP of a refrigerator are given. The power input to the refrigerator is to be determined. Assumptions The refrigerator operates steadily. Analysis Rearranging the definition of the refrigerator coefficient of performance and applying the result to this refrigerator gives kW 2.06 = = = s 3600 h 1 1.35 kJ/h 10,000 COP R in net, L Q W & & 6-48 An air conditioner with a known COP cools a house to desired temperature in 15 min. The power consumption of An air conditioner with a known COP cools a house to desired temperature in 15 min....
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- Spring '07