THERMAL-CONVECTION FOR HERSCHEL-BULKLEY F LUID IN THE ENTRANCE REGIONOF A DUCT

The thermal convection for Herschel-Bulkley fluids in duct is studied, theoretically in the case of constant physical properties, and experi mentally from wall temperature measurements. The results of the theore tical analysis show that the non-Newtonian correction depends on the f low behavior index n and on the Herschel-Bulkley number Hb. Velocity m easurements for isothermal and heating situation, reveal the incidence of the imposed thermal field on the flow structure. It is characteriz ed by an increase of shear rate at the wall, and of the size of the fl owing plug. Temperature measurements permit the study of the local hea t transfer. Finally a correlation is proposed taking into account the modification of the wall shear rate induced by the rheological propert ies, and the temperature dependent character of the fluid.