What does the Biot number represent physically?
The Biot number is the ratio of the internal resistance of a body to heat conduction to its external resistance to heat convection. Therefore, a small Biot number represents small resistance to heat conduction, and thus small temperature gradients within the body.
What does a small Biot number mean?
Because the Biot number is the ratio between the external resistance of a body to convection energy exchange and internal resistance to transmitting energy by conduction, a small Biot number implies low resistance to transmission by conduction, and therefore very low temperature gradients within the body; thus leading …
What does the Biot number compare?
It compares the resistance to heat transfer within and on the surface of a body. The Biot number provides a way to compare the conduction resistance within a solid body to the convection resistance external to that body (offered by the surrounding fluid) for heat transfer.
What is the physical significance of the Nusselt number?
Nusselt number represents the ratio of heat flux by fluid when heat is transferred through fluid layer by convection when fluid involves some motion to heat flux by fluid when heat is transferred through fluid layer by conduction when fluid is motionless.
What is the purpose of the Biot number?
The numerical value of Biot Number (Bi) is a criterion which gives a direct indication of the relative importance of conduction and convection in determining the temperature history of a body being heated or cooled by convection at its surface.
What is the significance of the Biot number?
Biot Number expresses the ratio of Heat Conduction Resistance through the solid mass to Heat Convection Resistance between the body and environment showing how the temperature varies from the mass interior to the atmosphere.
What is Biot number in mass transfer?
The Biot number is a dimensionless group that compares the relative transport resistances, external and internal. It arises when formulating and non-dimensionalizing the boundary conditions for the typical conservation of species/energy equation for heat/mass transfer problems.
Why is Biot number important?
How do I find my Biot number?
Biot number formula h [W/(m² * K)] is the heat transfer coefficient at the material’s surface, k [W/(m * K)] is the thermal conductivity of the material. Bi is the resulting Biot number.
Is higher Nusselt number better?
The larger the Nusselt number, the more effective the convection. A larger Nusselt number corresponds to more effective convection, with turbulent flow typically in the 100–1000 range. For turbulent flow, the Nusselt number is usually a function of the Reynolds number and the Prandtl number.
What does Schmidt number represent?
The Schmidt number Sc is defined as. (11.19) and represents the ratio between the kinematic air viscosity ν and the diffusivity of particles. In practice, Sc represents the ratio between the momentum diffusivity (linked to ν) and the mass diffusivity (linked to ).
What is the physical significance of the Biot number is the Biot number more likely to be larger for a highly conducting solid or a poorly conducting one?
Biot number represents the ratio of conduction resistance within the body to convection resistance at the surface of the body. The Biot number is more likely to be larger for poorly conducting solids since such bodies have larger resistances against heat conduction.