- Result: And that gives us an efficiency of approximately 27.9% which is closest to answer choice B.
- ✅ Answer: B
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Student questions asked in live office hours about this problem
OH 56
Q: For finding H2 (enthalpy after the pump) with 10°F subcooling at 14.7 PSI, can I use the saturated water steam table at 202°F to find HF = 170.14 BTU/lb instead of 212°F? Also, the notes show cycle efficiency of 24%, but I'm getting 26.7%—is that a typo?
A: Yes, both approaches work for finding HF: you can look it up directly at 202°F or use the value at 212°F and subtract 10 BTU/lb using ΔH = Cp·ΔT (since Cp for liquid water is 1 BTU/lb·°F). And you're correct—the 24% efficiency in the notes is an error; it should be 26.7%, which has now been corrected in the comments.