Experiment and prediction model study on pool boiling heat transfer of water in the electric field with periodically changing direction

Abstract

The pool boiling heat transfer performance of water could be greatly improved by the constant electric field with the bar electrode. While, the heat transfer of water enhanced by electric field with periodically changing direction is rarely involved. Therefore, the heat transfer performance of water, mechanism analysis and prediction model for heat transfer characteristic affected by the electric field with periodically changing direction were studied. Individually, the heat transfer coefficient (HTC) and critical heat flux (CHF) were compared. Meanwhile, the difference of droplet shape, size of contact angle, bubbles growth and detachment on heat transfer surface were analyzed. Besides, semi-empirical prediction models for HTC and CHF were proposed. Results show that the HTC and CHF are significantly enhanced with decrease of switch period. While, this enhancement is diminished with increase of heat flux. Furthermore, when compared to the constant direction electric field, mechanism analysis indicates that the electric field with periodically changing direction not only enhances the rate of boiling fluid wetting the boiling heat transfer surface, but also accelerates the growth and detachment of bubbles. Moreover, predicted curves of model agree well with the experimental data, and variation of surface tension is considered as the main factor affecting heat transfer.