The efficiency is given by
where W is the work done during four steps, Q is the energy that was passed
In this case, we can write
The work done during the isothermal expansion (1) is given by:
where n=1 mol, T1=331 K, V2=39.4 L, V1=19 L
Steps 2 and 4 are constant volume processes
The work done during the isothermal expansion (3) is given by:
where n=1 mol, T3=218 K, V4=39.4 L, V3=19 L
Heat enters the system only during processes (1) and (4) because the internal energy of the gas increases in step 4 while no work is done, and because the internal energy does not change during step 1 while work is done by the gas:
The heat that enters the system during this isothermal expansion is given by:
The heat that enters the system during the constant volume step 4 is given by
where Cv=21 J/K, T3=218 K, T4=331 K
We put (3)- (8) in (2) and got:
ɛ=15.2%
Answer:
15.2%
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