Nusselt Number


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Nusselt number

[′nu̇s·əlt ‚nəm·bər]
(physics)
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 ).
(thermodynamics)
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 ?
Such local values have been further averaged over the surface of a cylinder to obtain the surface averaged (or overall mean) Nusselt number as follows:
The numerical values of the Skin-friction and the Nusselt number are given in Table (1).
The angular variation of the local Nusselt number Nu on the surface of the sphere for different Prandtl numbers and for different interaction parameters are presented in Figures 4.
The influences of the magnetic parameter, the thermal radiation parameter, the non-Newtonian Prandtl number and the Eckert number on the velocity, temperature, the local skin-friction coefficient and the local Nusselt number have been studied in detail.
The Nusselt number was found to be proportional to the temperature gradient during the oscillating mode at the designated points and was in the decreasing tend as the time elapsed.
1 units with respected to previous one with reference to the graph for Nusselt number for air flow rate when the air temperature is 20[degrees]C as shown in figure 4.
The dimensionless Nusselt numbers on the non-insulated boundary walls of the triangular duct are calculated using the formula.
Inclusion of the holes beneath in the computational domain was found to reduce both the average Nusselt number and the friction coefficient.
Their results showed that heat transfer coefficient and Nusselt number of non-Newtonian nanofluid increased with increasing concentration of Xanthan solution.
Table 1 displays the values of the skin-friction coefficient and Nusselt number at the surface for different values of [[theta].
Given that the flow regime is always laminar and that the heat flux changes slowly along the pipe length, the Nusselt number can be taken as constant (Nu = 4.
The Nusselt number (Nu) at the inner and outer cylinders is shown in tables 5&6.