![]() Therefore, the Nusselt number represents the enhancement of heat transfer through a fluid layer due to convection relative to conduction across the same fluid layer. The preceding equation defines the Nusselt number. In the case of convection, the heat flux can be calculated using Newton’s law of cooling. ![]() In the case of conduction, the heat flux can be calculated using Fourier’s law of conduction. Heat transfer through the fluid layer will be by convection when the fluid involves some motion and conduction when the fluid layer is motionless. H is the convective heat transfer coefficient įor illustration, consider a fluid layer of thickness L and temperature difference ΔT. K f is a thermal conductivity of the fluid The Nusselt number is to the thermal boundary layer what the friction coefficient is to the velocity boundary layer. The conductive component is measured under the same conditions as the heat convection but with stagnant fluid. The Nusselt number is named after a German engineer Wilhelm Nusselt. Nusselt number is equal to the dimensionless temperature gradient at the surface, and it provides a measure of the convection heat transfer occurring at the surface. Both numbers are used to describe the ratio of the thermal energy convected to the fluid to the thermal energy conducted within the fluid. The Nusselt number is a dimensionless number closely related to the Péclet number. ![]()
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