HVAC · Practice-Exam-1 · Problem 79PDFSolution in PDF ↓
HVAC · Practice-Exam-1 · Problem 79
Problem & Solution
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Problem: 25 GPM of water at 300 PSIA and 250 degrees goes through a boiler where it is converted to 500 PSIA steam at a thousand degrees.
Key step: 25 GPM of water at 300 PSIA and 250 degrees goes through a boiler where it is converted to 500 PSIA steam at a thousand degrees.
Watch out: So the only thing we don't know is H1, the enthalpy for the entering condition.
Result: equals m.delta h, or expanding that a bit, we can say, row times Q.delta h.
✅ Answer: C
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Student questions asked in live office hours about this problem
OH 124 · July 6, 2026
Q: Is there a better way to find the real specific volume or density than averaging nearby table values?
A: Interpolation or extrapolation is expected for this type of property lookup. Dan recommends either setting up a small table and doing the algebra while sense-checking the result, or learning the interpolation/extrapolation workflow on the calculator so the method is reliable under exam conditions.