I am a designer at a manufacture company. I am new to the field and I am trying to select a fan with the right static pressure requirement for the duct work. The fan should around 5500 cfm. I was reading ACGIH to get more information and I found the equation Fan Static...
So I found the following equation from ACGIH: Principle of Ventilation
Fan Total Pressure=TP(outlet)-TP(inlet)=SP(outlet)+VP(outlet)-SP(inlet)-VP(inlet)
Fan Static Pressure=FTP-VP(inlet)=SP(outlet)-SP(inlet)-VP(inlet)
The fan I am using is a centrifugal fan that exhaust directly outside the...
I am a little bit confused on this: After pressure balance by design, how could there be a critical path (since all paths have the same pressure loss now)? I am designing a local exhaust system and each path starts from the terminal to the exhaust fan.
Hi Willard3 would you elaborate a little bit more? I have seen this equation: SP(fan)=SP(outlet)-SP(inlet)-VP(inlet). Is this what you are referring to?
To select a fan with the right static pressure, should I just use the pressure loss of the critical path or add up pressure losses from all the duct sections?
I am trying to locate the operating point for a multi-branch system. For the system curve, should I use a composite curve from all the branches or should I just use the critical path? Thanks!
Thanks guys! So to clarify: I will need to calculate static pressure losses for each branch. Static pressure loss at each branch is consisted of frictional losses (major head due to viscosity) and dynamic losses (minor head due to fittings)?
Thanks Drazen. That's what I thought too. I was reading ASHARE Handbook-Fundamentals and there is a section where the diameter of one of the duct is decreased incrementally until the pressure at the junction is balanced. But how do you calculate the pressure after each branch? Is it static pressure?
Is pressure balance at duct work junction required only for equal friction method? I used equal velocity method to size my duct, do I need to balance pressure at junctions?
