Wrong calculation methods description for piping systems

[Anonymous]

Hi All,

I've found some wrong description in Calculation Method in Mechanical Settings. When I select one of listed calculation methods and then go to read description of each method, I've found that gc = gravitational constant have wrong description. In ASHRAE Handbook is whole description about pressure drop equations and there is writen that gc = units conversion factor.   

How is that possible?!

This description isn't only wrong in Pipe Settings, but also in Duct Seetings for Pressure drop. 

Mechanical Settings in Revit 2015 and Calculation method description :

ASHRAE Handbook: Description of pressure drop equations:

In Colebrook Equation I've some remarks about equation. On picture below red circled, what does it suppose to mean. Is it v*f or is it  SQRT( f )?

Description of Colebrook equation in Revit:

Correct description of Colebrook equation:

Regards,

Dominik

[pteague]

The description may not match what the ASHRAE handbook says, but it is correct.  32.2 ft/s^2 is the gravitational constant.  Just because ASHRAE calls it "unit conversion factor" doesn't mean that it's not the gravitational constant.

The second issue you note is not really an issue.  That symbol before the f is a sqrt symbol.  Text symbols can't overlap each other so the bar that usually extends from the top of the sqrt symbol is cut off.

[chrisplyler]

It's because the factor which is used to convert units in these calculations IS the gravitational constant. Well, except that it's only kinda constant, at least generally speaking, within some tolerance level, near the surface of the Earth.