Darcy-Weisbach. It's a phrase you are probably hearing more and more of. What is it? It is a formula for calculating friction loss just like Hazen-Williams. But whereas Hazen-Williams is used for water in sprinkler pipe, Darcy-Weisbach can be used for any liquid (including water, but NFPA 13 does not permit its use).
Its recent popularity is due to new fluids that have been produced for use in antifreeze systems. In order to calculate these systems you will need to know some things about the fluid being used, specifically the Density and the Viscosity. The Density is in the units of lbs per cubic foot (kg per cubic meter) and the Viscosity is the units of centipoise. These need to be entered in the appropriate spots in the calculation dialog box.
For more information on Darcy-Weisbach vs. Hazen-Williams see a great comparison article from Scott Martorano of The Viking Group in PDF form at: Darcy-Weisbach Article
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