Nusselt Number

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Nusselt number

[′nu̇s·əlt ‚nəm·bər]
A dimensionless number used in the study of mass transfer, equal to the mass-transfer coefficient times the thickness of a layer through which mass transfer is taking place divided by the moleculor diffusivity. Symbolized Num ; NNu m . Also known as Sherwood number (NSh ).
A dimensionless number used in the study of forced convection which gives a measure of the ratio of the total heat transfer to conductive heat transfer, and is equal to the heat-transfer coefficient times a characteristic length divided by the thermal conductivity. Symbolized NNu .

Nusselt Number


a dimensionless parameter that characterizes the intensity of convective heat exchange between the surface of a body and a flow of gas (or liquid). It is named after the German physicist W. Nusselt (1882–1957). The Nusselt number Nu = αl/λ, where α = Q/(S · ΔT) is the heat-exchange coefficient, Q is the heat transfer across the surface of the body per unit time, ΔT > O is the difference of temperature between the surface of the body and the gas (or liquid) measured outside the boundary layer, S is the area of the surface, l is a characteristic dimension, and λ is the coefficient of thermal conductivity of the gas.

References in periodicals archive ?
The results showed that the averaged Nusselt numbers decrease with increasing jet-to-plate spacing when 1 < H/d < 4.
7) The local data obtained with the TLCs were averaged over the rectangular sensor area for comparison with the Nusselt numbers obtained by measurements with the heat flux sensor.
For all stable cases that have been investigated, the mean Nusselt numbers increase very slightly as a function of Rayleigh number.
It was found that the average Nusselt numbers with uniform energy dissipation (UED) in the cylinder were about 11% lower than those with constant heat flux (CHF) boundary condition and approximately 4% higher than those with constant surface temperature (CST) boundary condition.
The Nusselt numbers are found from the correlations given in (4) for each surfaces.
The current work concentrates on understanding the scaling that influences the creation of these two distinct regions, and the development of predictive correlations for both friction factors and Nusselt numbers.
Based on a roughness-viscosity model, they explained that the numerically predicted Nusselt numbers are smaller than the experimentally determined ones.
The performance of these jets is evaluated in terms of the measured increases in the values of the local Nusselt numbers and the uniformity of their radial distributions on the impinged surface.
Laminar flow regimes in the peripheral pipes giving constant Nusselt numbers and almost constant heat transfer coefficients make the average borehole thermal resistance of the multi-pipe design vary very little with the flow rate.
In the laminar region of Reynolds number investigated, the measured local Nusselt numbers agreed with classical developing flow theory.