Graetz Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Graetz number, abbreviated Ga, is a dimensionless number that characterizes laminar flow with heat transfer in a conduit.    This number is used to determine the thermal development on the entrance to ducts.  A Graetz number of 1000 and below is usually where a flow is considered thermally developed.  The calculation and formula for the Graetz number is below.

\(\large{ Gz = \frac {D_h}{l} Re Pr }\)         

Where:

\(\large{ Gz }\) = Graetz number

\(\large{ D_h }\) = hydraulic diameter

\(\large{ l }\) = length

\(\large{ Re }\) = Reynolds number

\(\large{ Pr }\) = Prandtl number

 

 

Tags: Equations for Heat Transfer Equations for Heat