EFFECT OF NONUNIFORM ELECTRIC-FIELDS ON CONVECTIVE HEAT-TRANSFER IN ACOLLOIDAL FLUID

The effect of radial electric fields on the convective heat transfer c oefficient of a colloidal fluid (haematite in distilled water) has bee n studied as a function of various quantities such as time, electric f ield, pH value, colloidal concentration and orientation. The electroco nvective heat transfer coefficient exhibits a 'timing' effect as well as an 'aging' effect. Whereas an AC field always enhances the heat tra nsfer, a DC field produces an enhancement that is almost vertical in t he vicinity of the origin. An increase in particle concentration incre ases the heat transfer coefficient, while a sharp rise in heat transfe r coefficient is observed when the surface charge of the collidal part icle is increased. Furthermore, the convective heat transfer coefficie nt increases when the inclination of the cylinder is changed from the horizontal to the vertical position.