Problem: The pressure loss in a duct is 1.2 inches water gauge when the flow rate is 2500 CFN.
Given: 1.2 inches water gauge when the flow rate is 2500 CFN; 1.2 inches and the volume flow rate is 2,500 CFN; 1.2 inches w...
Approach: So you can look up fan laws or affinity laws in the reference handbook and you'll find some useful formulas for this.
Calc: So condition 1, condition 2, just make a table and capture all the given information in a table.
Calc: The pressure is going to be given in units of inches water gauge and the initial condition is that the pressure is 1.2 inches a...
Result: So if it had been a linear relationship then this would have been 80% 80% of 1.2 would have been right around 1 we'd be looking at answer choice B ...
Office Hours
1
Student questions asked in live office hours about this problem
OH 19: HVAC 10
Q: For HVAC-10 (fan affinity laws), the reference handbook seems to have errors in some of the fan law equations — which ones can I trust?
A: I haven't done a full audit of all the fan law equations in the handbook, but the fundamental principles in 1A, B, and C are solid — and those are what matter for the exam. Extract the underlying principles from those relationships; if you understand the physics, you can reconstruct the equations even if one is written incorrectly somewhere in the handbook.