Temperature and friction factors
Temperature and friction factors
(OP)
Hi there,
Today I am posting a double.
I red this interesting post, thread378-227715: friction factor and materials, where I could find an exhaustive information concerning possible formulas for friction factors.
I'd have following questions: each of these formulas are affected indirectly by temperature.
Temperature influences density and viscosity, that are included in Reynolds number.In theory this would account for temperature change.
My question is: does any of this correlation loose precision when we are dealing in temperatures of water around 180F instead than when we are working with temperatures of 50F or vice versa?
Many thanks
Today I am posting a double.
I red this interesting post, thread378-227715: friction factor and materials, where I could find an exhaustive information concerning possible formulas for friction factors.
I'd have following questions: each of these formulas are affected indirectly by temperature.
Temperature influences density and viscosity, that are included in Reynolds number.In theory this would account for temperature change.
My question is: does any of this correlation loose precision when we are dealing in temperatures of water around 180F instead than when we are working with temperatures of 50F or vice versa?
Many thanks





RE: Temperature and friction factors
The real trick looked like it was going to be solving for a temperature-dependent viscosity. In the slide-rule days we always skipped that step and just used the same viscosity everywhere. I recently did a comparison of a dozen different empirical equations for gas viscosity as a function of density. I compared them to the values from NIST RefProp.exe and found that allowing dynamic viscosity to vary from 25% of NIST to 200% of NIST gave me a variance in flow rate of less than 5% for the new plastic pipes and 15% for commercial steel pipes. After a week of messing with this stuff I determined that we were closer to "right" with holding viscosity constant than the new guys are by working so hard to quantify changes.
David
RE: Temperature and friction factors
We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer