HVAC · Heat-Transfer · Problem 13PDFSolution in PDF ↓
HVAC · Heat-Transfer · Problem 13
Problem & Solution
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Problem: What is the viscosity of 150 degree water?
Given: 5 pound force second per foot squared; 32.2 feet per second squared; 32.2 pound mass times foot times second squared
Approach: So this may at first look like a fluids problem and maybe it is.
Calc: So we have the absolute dynamic viscosity on one hand, which for 150 degrees is mu equals 0.95 times 10 to the minus 5 pound fo...
Calc: This is 0.476 times 10 to the minus 5 foot squared per second.
Result: So there's these little tangents that are off the beaten path and it's not something that you can just know, right, something you kind of have to f...
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Student questions asked in live office hours about this problem
OH 47: HVAC: Heat Transfer-13
Q: In Heat Transfer 13 (dynamic viscosity), is there any underlying logic to multiplying kinematic viscosity by density and time to get dynamic viscosity — or was this just lucky unit manipulation?
A: Not lucky at all — what you did is apply the definition of kinematic viscosity (ν = μ/ρ), rearranged to μ = ν × ρ, which is exactly the right approach. My only suggestion is to use the density at 150°F (the stated water temperature) rather than the standard 62.4 lb/ft³, and convert units carefully so the answer is in lb_m/ft·hr as required.