Abstract
The fully established friction factors and heat transfer coefficients of the laminar flow of viscoelastic fluids in a 5:1 rectangular duct were measured experimentally. The bottom wall, one of the longer sides of the duct was heated by passing direct electric current through it, yielding constant peripheral wall temperature and constant heat input per unit length along the bottom wall. The other surfaces were adiabatic. The test section is 150 hydraulic diameters long. Aqueous solutions of two different polymers (polyacrylamide and hydroxyethylcellulose) were used as viscoelastic fluids. The measured laminar friction factors agree well with the Newtonian correlation when plotted as a function of Kozicki generalized Reynolds number (i.e., f=16/ Re ∗ ). The established laminar Nusselt values for aqueous solutions of hydroxyethylcellulose, a weakly elastic fluid, are not significantly different from the values for water when compared at about the same values of Prandtl number and Rayleigh number. The Nusselt numbers for polyacrylamide solutions are about 25% higher than those for water at comparable values of Prandtl number and Rayleigh number.
Published Version
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