HVAC · Systems-and-Components · Problem 23PDFSolution in PDF ↓
HVAC · Systems-and-Components · Problem 23
Problem & Solution
Video Synthesis
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Office Hours
3
Student questions asked in live office hours about this problem
OH 21: HVAC: Systems-23
Q: I used equation 9.3.8.4 and got 1.11 horsepower — is there a correction for non-standard conditions?
A: Take a look at the written and video solutions first — I think once you see the approach there, it'll clarify where your method diverged. The important thing is that you tried a different method; sometimes those lead somewhere valid, sometimes not, and working through why is part of how you build judgment.
OH 39: HVAC: Systems And Components-23
Q: Where can the Air Horsepower equation be found in the reference handbook?
A: Search for 'fan power' — searching for 'air horsepower' or 'HP' will send you on a wild goose chase. Once you're in the fan section, the formula will be right there.
OH 42: HVAC: Systems And Components Module #23
Q: Why don't you correct for air density at 5,000 feet when using the fan affinity law to find brake horsepower?
A: There are actually two equations at play: the sensible heat equation to find CFM (which inherently assumes standard density in the 1.1 coefficient), and the fan power equation. The density correction for altitude affects the power calculation differently than it affects the airflow calculation, and you should understand which equation is sensitive to density and which isn't. Work through the problem once at sea level and once at altitude to see where the numbers diverge.