Heat transfer coefficients for the laminar fully developed flow of viscoplastic liquids through annuli

Heat transfer during the laminar fully developed axial flow of viscoplastic materials through concentric annular spaces was studied experimentally. The thermal boundary conditions were insulated outer tube wall and uniform heat flux at the inner tube wall. The flowing liquids were Carbopol aqueous solutions at different concentrations, whose flow curves were well represented by the Herschel–Bulkley viscosity function. The effect of yield stress and power-law exponent on the Nusselt number is investigated. It is shown that the effect of rheological parameters on the inner-wall Nusselt number is rather small.