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 ?
The Nusselt number in single or co-rotative twin-screw screw extruders is of the same order of magnitude [29-31].
Table compares the mean Nusselt number of MACB scheme and experimental results.
The results of maximum Nusselt number showed a developing near the side-wall, and it moves further downstream.
Comparing the Nusselt number at Re = 1000 to Re = 3000 shows an increase of more than two times the convective heat transfer.
The condensation heat transfer coefficients were calculated from two-phase Nusselt number ([Nu.
Temperature gradient is approximated by the gas Nusselt number, hydraulic diameter, and temperature difference between deposit surface temperature and gas temperature, as given in equation (12)
alpha]] is typically calculated by a Nusselt number correlation for a circular cylinder in cross flow For this the authors propose the following correlation, which was derived from previous CFD LES investigations of wall mounted cylinders with low height/diameter ratio in steady-state flow:
1]: Navier slip coefficient Nu: Nusselt number Pr: Prandtl number Q: Heat generation/absorption Rd: Thermal radiation parameter [Re.
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.
The Gnielinski factor is used to calculate the Nusselt number using the Reynolds and Prandtl numbers.
Nu Nusselt number based on outside diameter of smooth tube d / k
7, 8]) claim that the presence of nanoparticles in a fluid alters the flow structure and increases the natural convection mean Nusselt number for any given characteristic (i.