P21_041 - 41. The efficiency of the engine is defined by...

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Unformatted text preview: 41. The efficiency of the engine is defined by ε = W/Q1 and is shown in the text to be ε = (T1 − T2 )/T1 , so W/Q1 = (T1 − T2 )/T1 . The coefficient of performance of the refrigerator is defined by K = Q4 /W and is shown in the text to be K = T4 /(T3 − T4 ), so Q4 /W = T4 /(T3 − T4 ). Now Q4 = Q3 − W , so (Q3 − W )/W = T4 /(T3 − T4 ). The work done by the engine is used to drive the refrigerator, so W is the same for the two. Solve the engine equation for W and substitute the resulting expression into the refrigerator equation. The engine equation yields W = (T1 − T2 )Q1 /T1 and the substitution yields Q3 Q3 T1 T4 = −1= − 1. T3 − T4 W Q1 (T1 − T2 ) Solve for Q3 /Q1 : Q3 = Q1 T4 +1 T3 − T4 T1 − T2 T1 = T3 T3 − T4 T1 − T2 T1 = 1 − (T2 /T1 ) . 1 − (T4 /T3 ) ...
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This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.

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