A power
cycle produces 2.4 x 10^{8} Btu and rejects 7.1 x 10^{8} Btu of heat
to the surroundings.
Calculate the thermal efficiency of the cycle. 





Read : 
This one is a
straightforward application of the definition of the the 1st
Law and the efficiency of a power cycle. 












Diagram : 













Given: 
W_{cycle} 
2.4E+08 
Btu 



Q_{C} 
7.1E+08 
Btu 












Find: 
h_{cycle} 
??? 



















Assumption: 
1  
The cycle only exchanges heat with the two thermal
reservoirs. 












Equations
/ Data / Solve: 




















1st
Law applied to the heat
engine: 


Eqn 1 













Definition of thermal efficiency : 




Eqn 2 













Degree
of freedom analysis: 2
eqns in 2 unknowns: Q_{H} and h. 
















Solve Eqn 1 for Q_{H} : 




Eqn 3 



















Q_{H} 
9.5E+08 
Btu 













Next, plug numbers into Eqn 2 : 



h 
0.2526 
























Verify: 
The only assumption
cannot be verified. 

















Answers : 
h 
25.3 
% 


















































