# Hagen Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Hagen number, abbreviated Hg, is a dimensionless number that is used in forced flow calculations.  The equation is similar to the Grashof Number but for forced flow rather than natural convection.

## formulas that use Hagen number

 $$\large{ Hg = \frac { 1 } { \rho} \; \frac { d p } { d x} \; \frac { l^3 } { \nu^2} }$$

### Where:

$$\large{ Hg }$$ = Hagen number

$$\large{ \rho }$$  (Greek symbol rho) = density

$$\large{ \nu }$$  (Greek symbol nu) = kinematic viscosity

$$\large{ l }$$ = length

$$\large{ d p }$$ = pressure differential

$$\large{ \frac { d p } { d x} }$$ = pressure gradient

$$\large{ d x }$$ = distance between pressure centers