301 Sample_Test_3_Solution

301 Sample_Test_3_Solution - SOLUTIONS MAE 301: Engineering...

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SOLUTIONS 1 MAE 301: Engineering Thermodynamics I Spring 2010 Test 3 (15% of final grade) April 22, 2010 Problem 1. (25 points) (a) The COP of a reversible heat pump operating between two thermal reservoirs is equal to 4. What is the efficiency of a reversible heat engine operating between the same temperature reservoirs? (b) Select a correct relation for an irreversible heat engine cycle operating between two temperature reservoirs: 0 > L L H H T Q T Q ; 0 = L L H H T Q T Q ; 0 < L L H H T Q T Q Solution: (a) 25 . 0 1 75 . 0 4 1 1 = = = = = H L H L H L HP T T T T T T COP η (b) For a irreversible heat engine 0 0 ; 0 < > + = = Δ L L H H gen gen L L H H T Q T Q S S T Q T Q S Problem 2. (25 points) A heat pump cycle is used to maintain the interior of a building at 20 ˚C. At steady state, the heat pump receives energy by heat transfer from well water at 10 ˚C and discharge energy by heat transfer to the building at a rate of 120,000 kJ/h. Over a period of 14 days, an electric
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301 Sample_Test_3_Solution - SOLUTIONS MAE 301: Engineering...

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