Graetz number
Encyclopedia
In fluid dynamics
, the Graetz number,
is a dimensionless number that characterises laminar flow in a conduit. The number is defined as:
where
is the diameter in round tubes or hydraulic diameter in arbitrary cross-section ducts
is the length
is the Reynolds number and
is the Prandtl number.
This number is useful in determining the thermally developing flow entrance length in ducts. A Graetz number of approximately 1000 or less is the point at which flow would be considered thermally fully developed.
When used in connection with mass transfer the Prandtl number is replaced by the Schmidt number
which expresses the ratio of the momentum diffusivity to the mass diffusivity.
The quantity is named after the physicist Leo Graetz
.
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
, the Graetz number,
is a dimensionless number that characterises laminar flow in a conduit. The number is defined as:where
is the diameter in round tubes or hydraulic diameter in arbitrary cross-section ducts is the length is the Reynolds number and is the Prandtl number.This number is useful in determining the thermally developing flow entrance length in ducts. A Graetz number of approximately 1000 or less is the point at which flow would be considered thermally fully developed.
When used in connection with mass transfer the Prandtl number is replaced by the Schmidt number
Schmidt number
Schmidt number is a dimensionless number defined as the ratio of momentum diffusivity and mass diffusivity, and is used to characterize fluid flows in which there are simultaneous momentum and mass diffusion convection processes...
which expresses the ratio of the momentum diffusivity to the mass diffusivity.The quantity is named after the physicist Leo Graetz
Leo Graetz
Leo Graetz was a German physicist. He was born in Wrocław , Poland as the son of the historian Heinrich Graetz.Graetz was one of the first to investigate the propagation of electromagnetic energy...
.