Colburn number

Physical key figure
Surname	Colburn number
Formula symbol	${\displaystyle J}$
dimension	dimensionless
definition	${\displaystyle J={\frac {\alpha }{\rho \;c_{p}\;u}}\left({\frac {c_{p}\;\eta }{\lambda }}\right)^{\frac {2}{3}}}$
${\displaystyle \alpha }$ Heat transfer coefficient ${\displaystyle \rho }$ density ${\displaystyle c_{p}}$ specific heat capacity ${\displaystyle u}$ Flow velocity ${\displaystyle \eta }$ dynamic viscosity ${\displaystyle \lambda }$ Thermal conductivity
Named after	Allan Colburn
scope of application	Convection of viscous fluids

The Colburn number ( symbol ) is a dimensionless number of fluid mechanics . It characterizes the heat transfer of viscous fluids with free convection and forced convection . It is named after the American chemical engineer Allan Philip Colburn (1904–1955). ${\displaystyle J}$

The Colburn number can be calculated from the heat transfer coefficient , the density , the specific heat capacity at constant pressure, the flow velocity , the dynamic viscosity and the thermal conductivity as: ${\displaystyle \alpha }$ ${\displaystyle \rho }$ ${\displaystyle c_{p}}$ ${\displaystyle u}$ ${\displaystyle \eta }$ ${\displaystyle \lambda }$

${\displaystyle J={\frac {\alpha }{\rho \;c_{p}\;u}}\left({\frac {c_{p}\;\eta }{\lambda }}\right)^{\frac {2}{3}}}$

or composed of other key figures:

${\displaystyle J={\frac {\mathit {Nu}}{{\mathit {Re}}\,{\mathit {Pr}}^{\frac {1}{3}}}}={\mathit {St}}\,{\mathit {Pr}}^{\frac {2}{3}}}$

Here stands for the Nusselt number , for the Reynolds number , for the Prandtl number and for the Stanton number . ${\displaystyle {\mathit {Nu}}}$ ${\displaystyle {\mathit {Re}}}$ ${\displaystyle {\mathit {Pr}}}$ ${\displaystyle {\mathit {St}}}$

literature

• Achim Lechmann: Modeling of heat exchangers in the gas exchange systems of internal combustion engines . Diss. Berlin 2008 ( Online [PDF; 8.1 MB ]).

Individual evidence

1. ^ ^{A b} Josef Kunes: Dimensionless Physical Quantities in Science and Engineering . Elsevier, 2012, ISBN 978-0-12-391458-3 , pp. 190 ( limited preview in Google Book Search).