Numerical Investigation of Entrance Region Flow Heat Transfer of Viscoplastic Fluids in Rotating Concentric Annuli

Abstract

The study of the entrance region flow, sometimes called entry length problem, is of considerable technical importance due to its immediate application in various designs of those chemical, biomedical and food processes in which the flows of Newtonian and non-Newtonian fluids are encountered. Furthermore, such an entrance flow is encountered in almost every industrial process involving non-Newtonian suspensions, emulsion or solutions. In recent times, experimental researches have shown clear evidence that the use of nonNewtonian fluids with variable viscosity can improve the fluid properties relative to that of fluids with constant viscosity. Particularly, Rheologists intend to use non-Newtonian fluids characterized by an yield value called viscoplastic fluids. Some of the important fluids which belong to this class are Bingham plastic, Casson fluid and Hershel-Bulkley fluids. The present work is on the study of the entrance region flow heat transfer of viscoplastic fluids in rotating concentric annuli. The analysis has been carried out over the wide range of non-Newtonian fluid flow parameters and geometrical considerations. The development of boundary layer is visualized when the fluid enters an annulus and the fully developed velocity profile is observed in the region starting from the point down-stream where the boundary layers meet asymptotically with the outer edge of the plug flow zone. The effects of non-Newtonian flow characteristics and geometrical characteristics on the velocity profiles, pressure variation and temperature distribution along the radial direction have been discussed.