Flow Pattern and Heat Transfer in a Cylindrical Annulus Under 1 g and Low-g Conditions: Experiments
Résumé
We investigate the thermal convection in an annular cavity, with differentially heated inner and outer cylinders, under the influence of a dielectrophoretic (DEP) force. Applying a temperature gradient to a liquid creates buoyancy driven thermal convection. When additionally a radially acting DEP-force is applied by means of an alternating electric field, the pattern of this convective flow changes which also leads to a change in the heat transfer. Depending on the parameters, e.g. an axisymmetric structure with toroidal vortices appears. Another possible structure are columnar vortices, which extend through the annulus. To isolate the effect of the DEP-force, this experiment is not only conducted in the laboratory, but also in microgravity conditions during parabolic flights. By using DEP-induced convective flows in microgravity a comparable heat transfer as with buoyancy convection under Earth’s condition can be obtained. A better understanding of the heat transport mechanisms inside a dielectric liquid confined between two concentric cylinders can deliver solutions for the improvement of the heat transport in many technical applications.