HVAC · Heat-Transfer · Problem 18PDFSolution in PDF ↓
HVAC · Heat-Transfer · Problem 18
Problem & Solution
Video Synthesis
Problem: Heat transfer 18 in the summer, a warehouse is maintained at 72 degrees by several chilled beams supplied with 58 degree chilled water which return...
Given: 18 in the summer, a warehouse is maintained at 72 degrees by several chilled beams supplied with 58 degree chilled wa...
Approach: And a chilled beam is interesting because it's a passive device.
Calc: In this case 58 degrees and the water is being returned at 65 degrees so the flow is in this direction.
Calc: We'd say okay the temperature in the space is 74 75 degrees and then we cool it down to 55 degrees or 60 degrees and that's mec...
Result: And that is 14 minus 7 divided by the natural log of 14 over 7, natural log of 2 that's 7 over the natural log of 2 which is 10.1 And that is close...
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Student questions asked in live office hours about this problem
OH 72: HVAC: Heat Transfer-18
Q: For Heat Transfer 18 (chilled beam modeled as a heat exchanger), the answer choices feel unrealistically close — I barely reached answer C with reasonable assumptions; are choices this tight representative of the real exam?
A: This problem was modeled after a real problem I encountered, so yes, it is representative — the close answer choices are intentional because this is a hard problem requiring careful application of the heat exchanger method with one fluid at constant temperature. A small error in assumptions will push you to the wrong answer choice, which is exactly the kind of discrimination the exam tests.