HVAC · Systems-and-Components · Problem 8PDFSolution in PDF ↓
HVAC · Systems-and-Components · Problem 8
Problem & Solution
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Student questions asked in live office hours about this problem
OH 34: HVAC: SYSTEMS-8
Q: I put that on the right for you. Should I not use the reference handbook formula or should I just remember to use the difference in temperature how you teach it?
A: So I'm hearing a couple of things in your question. I'm hearing that you don't love the way it is in the handbook and that you're open to doing it the way that I've shown and also that you would like to know understand how they're proposing you do in the handbook. So I just want to reassure you that the way it's being shown in the handbook and the way I do it are aligned.
OH 121 · May 25, 2026
Q: In a counterflow heat exchanger with a hot stream entering at 160°F and a cold stream entering at 50°F, why isn't ΔTA = 160 - 50 and ΔTB = 100 - 70 (i.e., pairing entering with entering and leaving with leaving)?
A: In a counterflow heat exchanger, the two streams flow in opposite directions, so the hot stream's entering end is on the opposite side from the cold stream's entering end. This means ΔTA pairs the hot stream's entering temperature with the cold stream's leaving temperature, and ΔTB pairs the hot stream's leaving temperature with the cold stream's entering temperature — not the same-side pairing that applies to parallel flow.