ELECTRIC NUSSELT NUMBER IN A SUSPENSION OF SPHERICAL HEMATITE (ALPHA-FE2O3) PARTICLES

An experiment has been devised to evaluate the electric Nusselt number in a suspension of spherical hematite particles (hematite in distille d water). The experiment was conducted using a single platinum wire (d iameter=0.025 mm) mounted along the axis of a copper cylinder (diamete r=53 mm). The Nusselt number was evaluated for various experimental pa rameters such as time, electric field, frequency, orientation, charge and concentration of the colloidal particles. An increase in Nusselt n umber was observed in an ac field, and the increase was extremely shar p for pH values largely different from the isoelectric point (i.e.p.). A similar effect was also noted in a de field at a very weak field st rength. An increase in concentration of the colloidal particles increa sed the Nusselt number and a similar effect was also noted when the cy linder was moved from the horizontal to the vertical position. An atte mpt was made to evaluate the efficiency of convection using an empiric al relationship and the results for ac and de fields are presented.