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1. The problem statement, all variables and given/known data

Figure P22.53 represents n mol of an ideal monatomic

gas being taken through a cycle that consists of two

isothermal processes at temperatures 3Ti and Ti and two

constant-volume processes. For each cycle, determine, in terms of n, R, and Ti , (a) the net energy transferred

by heat to the gas and (b) the efficiency of an engine

operating in this cycle.

2. Relevant equations

3. The attempt at a solution

Now, I've solved part a), and get W = 2nRTln2 (difference between top and bottom portions), can't get part b). I know that efficiency = energy sought/ energy cost = W/Q_h, but they don't really specify in the question where the energy intake is, or energy cost. The answer is 0.273.... I've found that for each cycle:

the sides both equal dU = dQ = 3nRT, the top Q = 3nRTln2, bottom Q = nRTln2. Seems like the 'energy cost' based on e = .273 and W = 2nRTln2 should be 3+3ln2, no idea how that comes about though... perhaps somehow the 'cost' is over the top and side??

Ari

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# Homework Help: Thermo Efficiency question

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