Viscous dissipation and heat transfer in pulsatile flows of a yield-stress fluid

The convective heat transfer phenomenon due to viscous dissipation associated with the low Reynolds number pulsatile flow of a non-Newtonian inelastic fluid exhibiting a yield-stress (Bingham fluid) through a circular pipe is studied numerically. The problem is of interest in a number of industrial applications such as the processing of industrial slurries and plastic melts. The singularities due to the infinite value attained by the effective viscosity at zero rates of deformation is avoided by adopting a bi-viscosity model. The flow enhancement characteristic of the pulsatile flows of non-Newtonian fluids affects the associated heat transfer rates in the case of non-isothermal flows. The emphasis in this study is on investigating the effects of the fluid rheology, characterized by the yield number, as well as the frequency of the imposed pulsatile pressure gradient on the fluid flow and its heat transfer characteristics. The presented results reveal the instantaneous as well as the time averaged characteristics of the flow and heat transfer phenomena.