650_Physics ProblemsTechnical Physics

650_Physics ProblemsTechnical Physics - 652 P22.53 Heat...

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652 Heat Engines, Entropy, and the Second Law of Thermodynamics P22.53 (a) P electric = H t ET so if all the electric energy is converted into internal energy, the steady-state condition of the house is described by HQ ET = . Therefore, electric W == Q t 5000 (b) For a heat pump, COP K 27 K Carnot af = T T h 295 10 92 . Actual COP = = 0 6 10 92 6 55 .. . Q W Qt Wt hh Therefore, to bring 5 000 W of energy into the house only requires input power heat pump COP W 6.56 W = = W t h 763 P22.54 Q mc T mL mc T c =+ += ∆∆ Q Q Q W T TT W QT T T c c c c c hc ch c c =⋅ ° ° + × +⋅ ° ° = = ×° ° = 0500 10 20 208 10 200 273 20 0
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