Forums >> Revit Systems >> Technical Support >> Revit MEP Default Air Viscosity and Piping Roughness

louisvb

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Joined: Mon, Mar 16, 2009
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I've been digging to make sure the air properties in Revit work for our location and our company standards.  I'm a little confused, however.  The Air Viscosity given in the Mechanical Settings Dialog is 0.53 cP.  I've checked various sources and they all list the viscosity of air being about 0.018 cP.  The value of 0.53 cP is more on the order of what you would see from water.  Is this really dynamic viscosity or are they really looking for kinematic viscosity?  Or, is this 0.53 cP simply wrong?

I've also been checking into the piping roughness factors.  Again the default values given by Revit seem to be off of what is given in other literature.   For example, Revit has carbon steel with a roughness of 0.00180' and other sources give to me as 0.0002'.  And this is consistent with the other types of pipe.  Revit gives a number with about a factor of 10 or so off.  Is it possible that revit is asking for roughness factors in inches?

Has anyone else noticed this with these numbers?  Am I simply missing something with these various numbers or is there something wrong with Revit?  

I am using Revit MEP 2009.

Thanks,

Louis

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Eddieboarder91

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