HVAC · Practice-Exam-2 · Problem 39PDFSolution in PDF ↓
HVAC · Practice-Exam-2 · Problem 39
Problem & Solution
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Problem: In 8 foot long, 1 inch diameter solid aluminum alloy rod with a coefficient of linear thermal expansion of 12.8 times 10 to the negative 6th 1 over de...
Key step: We know the coefficient of thermal expansion is 12.8 times 10 to the negative 6 and that that has units of 1 over Fahrenheit degrees.
Watch out: I don't think it is quite this thick in physical appearance, but I'll work for our purposes.
Result: And that equals 3.2 times 10 to the negative 3 inches squared.
✅ Answer: A
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Student questions asked in live office hours about this problem
OH 102: HVAC: Full Practice Exam #39
Q: Are the equations for thermal expansion given anywhere in the manual or is this just one that needs to be memorized?
A: So thermal expansion, there's a table in the reference handbook 1.2.12. And that gives a bunch of the coefficient of linear expansion values for different metals and things. So that's the value of this alpha coefficient of thermal expansion.
OH 124 · July 6, 2026
Q: Is the diameter relationship used after the thermal elongation formula a structural concept that HVAC test takers need to memorize?
A: Dan framed it as a heat-transfer/thermal-expansion idea rather than a structural topic. Linear thermal expansion applies in any one dimension, so the same fractional change can be applied to length or diameter; HVAC examinees should understand that concept without overinvesting in structural study.