Multiphase Flow and Heat Transfer of Electrospray Droplets for Cooling

EasyChair Preprint no. 11549

Abstract

Electrospray cooling is recently a promising heat removal route for electronics due to its powerful cooling capacity, tiny liquid supply, and precise temperature control. Droplet impact and evaporation are the fundamental heat transfer processes of electrospray cooling and would be significantly affected by an applied electric field. This study experimentally investigated the impact behaviors and evaporation characteristics of single electrospray droplets on hot substrates. On the one hand, the visual results from the high-speed camera showed that the maximum spreading radium was proportional to the charge density of the impact droplet, which increased up to about 9.6% compared to neutral droplets. A prediction model of the maximum spreading ratio based on the impact velocity, droplet charge density, and substrate wettability was eventually established. On the other hand, the evaporation of sessile droplets under a needle-to-plate electric field was found dramatically accelerated. With increasing electric field intensity, the “depinning” and “tiny jet” phenomena near the three-phase contact line could be observed, accompanied by an extra constant contact angle (CCA) evaporation stage. As a result, the evaporation rate increased by about 6.8 times over the traditional condition. Theoretically, this enhancement mechanism of non-uniform electric field on droplet evaporation was basically attributed to the combined effects of corona wind blowing, surface tension weakening, and molecular orienting. This work contributed to a better understanding of the electrospray cooling technique and demonstrated an efficient way for high heat flux dissipation.

Keyphrases: Droplet, Electrohydrodynamic, evaporation, Impact behaviors, spray cooling

@Booklet{EasyChair:11549,
  author = {Haojie Xu and Junfeng Wang and Bufa Li and Tian Hu},
  title = {Multiphase Flow and Heat Transfer of Electrospray Droplets for Cooling},
  howpublished = {EasyChair Preprint no. 11549},

  year = {EasyChair, 2023}}