Graetz Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Graetz number, abbreviated as Ga, 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.


Graetz number calculator



Graetz number formula

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


 Units English Metric
\(\large{ Gz }\) = Graetz number \(\large{dimensionless}\)
\(\large{ D_h }\) = hydraulic diameter \(\large{ft}\) \(\large{m}\)
\(\large{ l }\) = length \(\large{ft}\) \(\large{m}\)
\(\large{ Re }\) = Reynolds number \(\large{dimensionless}\)
\(\large{ Pr }\) = Prandtl number \(\large{dimensionless}\)


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Tags: Heat Transfer Equations Heat Equations Calculators