Flow boiling characteristics of minichannel heat sink with artificial conical cavities array under electric field

Three kinds of minichannel heat sinks with artificial conical cavities array formed by ultrafast laser were designed and manufactured to explore flow boiling heat transfer performance of surface with artificial cavities under electric field. Using R141b as the working fluid, the effect of cavity parameters (diameter and density) and electric field (U' = 400 V, 600 V, and 800V) on heat transfer coefficient and flow instability at heat flux ranges from 1.93 kW/m(2) to 25.11 kW/m(2) were experimentally studied. Field trap effect on heat transfer surface with artificial conical cavities under electric field was further developed. The synergy effect of electric field and artificial cavity on enhancing flow boiling heat transfer was found. The mechanism of this can be attributed to field trap effect and enhancing disturbance effect of boundary layer around heat transfer surface. Visualization shows lots of small bubbles generating from bottom of artificial conical cavity, and process of bubble from nucleation to detachment in artificial conical cavity was discussed. The results show that the maximum heat transfer enhancement ratio of 1.99 appears at heat flux of 7.72 kW/m(2) for MCH-2 with an applied voltage of 800 V, and the standard deviation of total pressure drop for MCH-2 with electric field reduces about 31% comparing to MCH-1 without electric field. Flow instability has been improved for minichannel with artificial cavities array under electric field, due to more uniformly distributed artificial cavities and more unified artificial cavity structural sizes. (C) 2021 Elsevier Ltd. All rights reserved.