Heat transfer performance of water-based electrospray cooling

Abstract

Electrospray (ES) cooling is a promising technique for dissipating high heat fluxes due to its excellent heat transfer characteristics and high energy efficiency. Conventional sprays exhibit a low efficiency due to droplet rebound and require a high pumping power. These issues are resolved with electrospraying, in which fine droplets are dispersed and accelerated with an electric field, thereby improving the cooling efficiency with a relatively lower pumping power and a low overall system weight. In this study, we investigate the thermal performance of ES cooling with water as the working fluid using a single stainless-steel nozzle with an inner diameter Di = 410 μm. We use three different flow rates, Q = 200, 400, and 600 μL/min, with a wide range of applied ES potentials, V1 = 0–7 kV, to investigate various ES modes. The results show that an increase in the applied ES potential can improve the heat transfer performance by 12.58% and 6.65% in the single-phase and transition regions, respectively, while the improvement is insignificant in the nucleate boiling region and at the critical heat flux. The variations in the ES mode are examined in detail using sequential optical images captured by a high-speed camera. Dimensionless correlations for each cooling regime are proposed using the Weber, electric Weber, and modified boiling numbers. These correlations provide good predictions of the heat transfer performance for all applied ES potentials and flow rates with an overall mean absolute error of 2.96%.