Laminar forced convection

Only a small number of solutions for the laminar forced convection problem and experimental investigations are available in the literature with some variations in the associated thermophysical properties. To the authors knowledge, for example, no experimental study is available to clarify the effect of the Prandtl number on the heat transfer in micro-channels with different duct geometries. 

The effective diffusivities determined from limiting-current measurements appear at first applicable only to the particular flow cell in which they were measured. However, it can be argued plausibly that, for example, rotating-disk effective diffusivities are also applicable to laminar forced-convection mass transfer in general, provided the same bulk electrolyte composition is used (H8). Furthermore, the effective diffusivities characteristic for laminar free convection at vertical or inclined electrodes are presumably not significantly different from the forced-convection diffusivities. 

Specific correlations of individual film coefficients necessarily are restricted in scope. Among the distinctions that are made are those of geometry, whether inside or outside of tubes for instance, or the shapes of the heat transfer surfaces free or forced convection laminar or turbulent flow liquids, gases, liquid metals, non-Newtonian fluids pure substances or mixtures completely or partially condensable air, water, refrigerants, or other specific substances fluidized or fixed particles combined convection and radiation and others. In spite of such qualifications, it should be... 

Some Solutions for External Laminar Forced Convection... 

Consider laminar forced convective flow over a flat plate at whose surface the heat transfer rate per unit area, qw is constant. Assuming a Prandtl number of 1, use the integral equation method to derive an expression for the variation of surface temperature. Assume two-dimensional flow. 

Shah, R.K. and London, A.L., Laminar Forced Convection in Ducts, Academic Press, New York, 1978. 

Yang, K.T., Laminar Forced Convection of Liquids in Tubes with Variable Viscosity , J. Heat Transfer, Vol. 84, pp. 353-362, 1962. 

Oosthuizen, P.H., "Laminar Forced Convective Heat Transfer from Rectangular Blocks Mounted on Opposite Walls of a Channel , Numerical Methods in Thermal Problems, Vol. VI, Part 1, Proc., 6th Int. Conf., Swansea, U.K., July 3-7, pp. 451-461,1989. 

As explained in Chapter 1, natural or free convective heat transfer is heat transfer between a surface and a fluid moving over it with the fluid motion caused entirely by the buoyancy forces that arise due to the density changes that result from the temperature variations in the flow, [1] to [5]. Natural convective flows, like all viscous flows, can be either laminar or turbulent as indicated in Fig. 8.1. However, because of the low velocities that usually exist in natural convective flows, laminar natural convective flows occur more frequently in practice than laminar forced convective flows. In this chapter attention will therefore be initially focused on laminar natural convective flows. 

Compare the heat-transfer coefficients for laminar forced and free convection over vertical flat plates. Develop an approximate relation between the Reynolds and Grashof numbers such that the heat-transfer coefficients for pure forced convection and pure free convection are equal. 

A solution that was accurate to first order in the buoyancy parameter, Gr. for near-forced convective laminar two-dimensional boundary layer flow over an isothermal vertical plate was discussed in this chapter. Derive the equations that would allow a solution that was second order accurate in Gx to be obtained. Clearly state the boundary conditions on the solution. 

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