Convective heat transport in Viscoplastic material due to localized heating: An Experimental approach

Abstract

Viscoplastic materials are found extensively both in natural and manmade form. In this work experimental investigation of natural convection in viscoplastic fluid with partially heated bottom wall and continuous cooling of top wall in a square cross section enclosure has been carried out. Carbopol Ultrez 20 gel of various concentrations has been used as sample viscoplastic fluid. Conduction and convection phase of heat transport are identified. The results are presented in terms of temperature distribution across the fluid for different gel concentrations and heat input. The average Nusselt numbers are also discussed for different conditions. Onset of convection is delayed and convection strength is weakened with increase in test fluid yield stress. Steady state temperature difference between hot and cold wall shows linear behaviour with heat input for conduction regime and non-linear behaviour in convection regime. Fluid temperature in enclosure shows sharp gradient closure to thermally active walls.