Heat flux parameter, axial

Axial heat flux parameter Y The parameter Y, which replaces the heat flux shape factor in the CHF correlation, is not only a measure of the nonuniformity of the axial heat flux profile but also a means of converting from the inlet subcooling (AHin) to the local quality, X, form of the correlation via the heat balance equation. It is defined as... 

Y = axial heat flux profile parameter Y = subchannel imbalance factor... 

In this lecture, the effects of the abovementioned dimensionless parameters, namely, Knudsen, Peclet, and Brinkman numbers representing rarefaction, axial conduction, and viscous dissipation, respectively, will be analyzed on forced convection heat transfer in microchannel gaseous slip flow under constant wall temperature and constant wall heat flux boundary conditions. Nusselt number will be used as the dimensionless convection heat transfer coefficient. A majority of the results will be presented as the variation of Nusselt number along the channel for various Kn, Pe, and Br values. The lecture is divided into three major sections for convective heat transfer in microscale slip flow. First, the principal results for microtubes will be presented. Then, the effect of roughness on the microchannel wall on heat transfer will be explained. Finally, the variation of the thermophysical properties of the fluid will be considered. 

Experimental measurements of this heat transfer coefficient have been obtained by many investigators, including Kiang et al., 1976 Furchi et al., 1988 Dou et al., 1991, 1993 Ebert et al., 1993 and Wirth, 1995. Parameters that have been found to affect include gas velocity, solids flow rate (mass flux), mean particle diameter, axial location of the heat transfer surface along the height of the fluidized bed, radial location of the heat transfer surface across the bed, and physical dimension of the heat transfer surface. General characteristics noted from the collected data include... 

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