Heat and mass transfer in rheologically complex systems

Abstract

This chapter discusses the phenomena of heat and mass transport in processes involving rheologically complex materials, especially with regard to the implications of shear dependent viscosity and viscoelasticity of materials. The highly non-linear and strongly coupled nature of the field equations preclude the possibility of analytical results, and therefore, usually numerical solutions are sought, even for as simple a situation as that of laminar flow of a purely viscous fluid in a circular tube. The thermo-physical properties of the commonly used non-Newtonian materials are described. It is clear that in the laminar region the shear thinning enhances heat transfer and reduces pressure drop as compared with a Newtonian fluid. The temperature dependent viscosity facilitates the heating of fluids while it impedes the efficacy of cooling of fluids for shear thinning materials. While from a heat transfer standpoint, the circular geometry is the most efficient one but when pressure loss is also of concern, short pipe lengths are preferred.