[haydert]

hi

i want to solve turbulent flow in smooth channel and i have inlet temperature with magnitude of 293 k can i get the reference value 273 k ?

is the length in reference value is hydraulic diameter ?

[LuckyTran]

The reference values are only needed for post-processing of derived quantities. If you don't use these post-processes quantities you can ignore all the reference values.

Nusselt number needs a reference length and reference conductivity, so you should put the reference length into the reference value. For channel flows, this reference length is usually the hydraulic diameter. However, these are based on convention. There's no rule or law that says you have to use anything.

Heat transfer coefficient needs a reference temperature. Whatever your definition of htc is, you should specify that as the reference value.

And so on and so on...