Numerical study of flow and heat transfer behaviour of power-law non-Newtonian fluids in rectangular channels: Dissertation

This thesis presents numerical studies on the flow and heat transfer behaviour of power-law non-Newtonian fluids in rectangular ducts, and in extruder channels of rectangular cross-section. For both applications hydrodynamically and thermally fully developed flows are studied first, and subsequently more realistic situations involving the effects of thermal development, viscous dissipation and temperature-dependent viscosity are considered. All numerical computations are based on the finite element method, and a marching procedure in the streamwise direction is utilized in the thermally developing situations. A salient feature of the present numerical approach is that it employs higher-order elements with quartic polynomial interpolation functions for dependent variables. In all cases studied the numerical procedure adopted yields consistent performance with respect to mesh refinement, and comparisons with available analytical solutions show very good agreement. The influence of different factors, such as shear-thinning, viscous dissipation and temperature-dependent viscosity, is investigated. In the extrusion flow computations the importance of considering the recirculating flow and associated transverse convection is clearly established.