Happy 4th of July Everybody!
When in the course of human events it becomes necessary to calculate the Darcy-Weisbach friction factor… engineer’s often throw up their hands, go back to their old college textbooks, and say “about .02!” [Which normally isn’t off by more than a factor of 2 in either direction.] If you want to be more scientific about it, you can calculate the appropriate flow parameters and then refer back to your Moody Diagram to get a “real” answer. But now, thanks to the miracle of Excel, you can use your trusty old Moody Diagram AND have an instant answer at the push of a button. The Excel spreadsheet linked at the bottom of this page contains the Churchill Correlation equations for the friction factor along with a plot that has been carefully overlaid on top of a standard Moody diagram. Just enter your relative pipe roughness (ε/D) into the cell highlighted in red and the chart will update with the appropriate friction factor calculations. For a single-point value, enter your Reynold’s number into the cell highlighted in green, and your friction factor will be calculated in C8.
And now, back to the bar-b-q.