Did you know that the online Autodesk User's Guides provide a wealth of information? The Revit MEP 2011 User Assistance site covers everything from "What's New" to the details of how Revit MEP calculates the pressure drop in rectangular ducting.
Click here for all the details and an example which shows how Revit MEP calculates the pressure drop for a 100 foot segment of 36” x 24" rectangular duct carrying air flow of 12,000 CFM.
• Air Density = 0.0751 lbs/cu ft.
• Air Viscosity = 0.01805 cP (standard atmospheric air at 66 degrees F)
• Roughness = 0.0003' (medium smooth galvanized steel duct as defined by 2005 ASHRAE Handbook: Fundamentals, page 35.7)
Thanks to Paul Hristov, Ideate Tech (and MEP!) Expert, who forwarded this link from Martin Schmid, P.E., Member ASHRAE, Autodesk Industry Success Manager.
