TRANSIENT HEAT-TRANSFER IN A FLUID SPHERE TRANSLATING IN AN ELECTRIC-FIELD

The transient heat transfer in a fluid sphere translating steadily in a dielectric medium is numerically investigated. The energy equation with velocity components of combined translation-induced and electric field-induced internal motion is integrated by the Alternating Direction Implicit (ADI) method for the entire drop interior. Creeping flow is assumed and the preponderance of the thermal resistance is assumed completely in the dispersed phase. The enhancement of heat transfer due to internal motion induced by both drop translation and the electric field is given in terms of the Nusselt number. Nusselt numbers are plotted as a function of the Fourier number, the Peclet number, and a parameter E. The parameter E represents the ratio of electric field-induced flow strength to that of translation-induced flow. In general, the heat transfer rate is approximately doubled when the flow is dominated by the electric field as compared with the case where no electric field is applied. It is suggested that for large Peclet numbers, the electric field is negligible for E less than 0.5, while the translation is unimportant for E larger than 10. For small Peclet numbers, the electric field is of minor importance for E less than 2 and the translation is insignificant for E greater than 50. © 1990 by ASME.