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A larger Nusselt number corresponds to more active convection, with turbulent flow typically in the 100–1000 range. [2] A similar non-dimensional property is the Biot number, which concerns thermal conductivity for a solid body rather than a fluid. The mass transfer analogue of the Nusselt number is the Sherwood number.
The Sherwood number (Sh) (also called the mass transfer Nusselt number) is a dimensionless number used in mass-transfer operation. It represents the ratio of the total mass transfer rate (convection + diffusion) to the rate of diffusive mass transport, [1] and is named in honor of Thomas Kilgore Sherwood.
In convective heat transfer, the Churchill–Bernstein equation is used to estimate the surface averaged Nusselt number for a cylinder in cross flow at various velocities. [1] The need for the equation arises from the inability to solve the Navier–Stokes equations in the turbulent flow regime, even for a Newtonian fluid .
Nusselt number: Nu = heat transfer (forced convection; ratio of convective to conductive heat transfer) Ohnesorge number: Oh = = fluid dynamics (atomization of ...
Where Nu is the Nusselt number, defined as: = (/) where: q/A is the total heat flux, D b is the maximum bubble diameter as it leaves the surface, T s – T sat is the excess temperature, k L is the thermal conductivity of the liquid,
The Nusselt number is most useful in determining the convective heat transfer coefficient, whereas the Biot number is used in unsteady problems. This is a typical exam question. The " k {\displaystyle k} " in the Biot numer is of a solid, that in the Nusselt number of a fluid.
Ernst Kraft Wilhelm Nußelt (Nusselt in English; November 25, 1882, in Nuremberg – September 1, 1957, in Munich) was a German engineer. Nusselt studied mechanical engineering at Technische Universität München , where he got his doctorate in 1907.
is the gas film Lewis number (-), is the gas film specific heat at constant pressure (J.Kg −1.K −1) The droplet vaporization rate can be expressed as a function of the Sherwood number. The Sherwood number describes the non-dimensional mass transfer rate to the droplet and is defined as: [3]