Flow resistance and convective heat transfer by elastic turbulence in 1D/2D/3D geometries

Abstract

Inducing elastic turbulence is a promising method to intensify flow and heat transfer at low Reynolds number Re. Different geometries shall have great impacts on the occurrence of elastic turbulence and its heat transfer effect, which are however seldom investigated especially for flow in 3D geometry. This work conducts a comparative experimental study of the dimension effect on elastic turbulence on 3D, 2D and 1D geometries with similar hydraulic diameters. Polyacrylamide is used to induce elastic turbulence and the corresponding flow resistance and heat transfer performance are obtained for different geometries under laminar flow conditions. The results provide strong evidence that curvatures are necessary for the onset of elastic turbulence in 1D geometry as shown by similar flow resistance and heat transfer coefficient between the Newtonian and viscoelastic fluids. Comparing to the 2D geometry, flow in 3D geometry achieves both reduced pressure drop gradient and increased heat transfer at the same time due to the unique interaction of elastic stress with the torsion and rotation effects. New correlations of Nusselt number Nu and Weissenberg number Wi are proposed in curved geometries as Nu∝Wi2.2 and Wi1.9 for the 3D and 2D flow structures, respectively, under the boundary condition of constant heat flux. The mechanisms of flow and heat transfer of elastic turbulence in different geometries are also discussed to help further optimization.