Thermodynamics Quiz #6 Solution

# Thermodynamics Quiz #6 Solution - ˙ Q H = 0 6 T H − T L...

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650:351 Thermodynamics Doyle Knight Department of Mechanical and Aerospace Engineering Rutgers - The State University of New Jersey New Brunswick, NJ USA Tel: 732 445 4464 · Email: [email protected] OFce hours: Tuesday and ±riday, 9:00 am to 11:30 am and by appointment

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Quiz No. 6 A heat pump has a coefcient oF perFormance β = 0 . 5 β carnot and maintains a house at T H = 20 C while the house loses energy at ˙ Q = 0 . 6( T H T L ) kW. ±or a maximum oF 1 kW power input, ²nd the minimum outside temperature T L For which the heat pump is a sufcient heat source. Solution Applying the ±irst Law oF Thermodynamics to a control volume surrounding the house, it is evident that the heat pump must supply heat at the rate
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Unformatted text preview: ˙ Q H = 0 . 6( T H − T L ) The coefcient oF perFormance oF the heat pump is β ′ = rate oF energy sought rate oF work done = ˙ Q H ˙ W See p. 219 Thus, ˙ W = ˙ Q H β ′ = . 6( T H − T L ) β ′ ±or a Carnot heat pump, β ′ Carnot = T H T H − T L 650:351 Thermodynamics Page 1 Quiz No. 6 Since β ′ = 0 . 5 β ′ Carnot , ˙ W = . 6( T H − T L ) . 5 T H ( T H − T L ) − 1 = 1 . 2 ( T H − T L ) 2 T H Note that the units on both sides are kW Thus, T L = T H − r T H ˙ W 1 . 2 = 277 . 52 K = 4 . 37 ◦ C 650:351 Thermodynamics Page 2...
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## This homework help was uploaded on 04/04/2008 for the course 650 351 taught by Professor Doylenight during the Spring '08 term at Rutgers.

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Thermodynamics Quiz #6 Solution - ˙ Q H = 0 6 T H − T L...

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