What Larry is saying is a bench that both settling chambers (Before and after the orifice for by directional benches) are symmetrical and who's Beta ratio is no larger than .250, the PTS bench with a 3.490" internal orifice (650 CFM) has a .179 Beta ratio on the closest panels.Bakerlite wrote:What would be a good way to calculate that?larrycavan wrote:
I have said in the past and will continue to say until someone proves me wrong. The most accurate orifice flow bench is the one with the cabinet properly designed for the capacity of air it needs to move at the test pressure you need to move it at
Second, the air must approach the orifice at an equal speed, laminar form. (this is part of the issue with the MSD and SF 300/600 as the orifice is at a 45° angel and at higher depression/air speeds i do not believe the orifice is seeing uniform (fully developed) flow. most likely the reason for the reduction in calibration depression as from 25" to 28" the speed increases and the error goes up.
Rick