A 2ND LOOK AT ELECTROKINETIC PHENOMENA IN BOILING

In the article by V. Asch [J. Appl. Phys. 37, 2654 (1966)], experiment s were performed to study the influence of an electrostatic field on n ucleate boiling of Freon-113(R-113). We have found that Asch might not have properly considered the effects of his experimental setup and th erefore came to incorrect conclusions concerning electrophoretic and d ielectrophoretic forces. Asch's analysis of the electric field distrib ution led him to conclude that the dielectrophoretic forces were small , however, we show in this article that, in general, there are strong dielectrophoretic forces in the vicinity of the heater wire. This arti cle presents the results from a set of experiments performed with an a pparatus similar to that of Asch's with test fluids of R-113 and FC-72 . The experimental results show that vapor bubbles can be attracted to either the anode or cathode depending on the potentials with respect to the heater wire on which the boiling takes place. This is contrary to the results obtained by Asch which led him to conclude that the bub bles were always attracted to the anode. The bubble movement appears t o be the result of a combination of dielectrophoretic forces (which ar e very strong but highly localized), electrophoretic forces, and bulk electroconvective flow. Furthermore, the combined effects of these for ces away from the wire can lead to unstable behavior. (C) 1996 America n Institute of Physics.