Electrospray cooling characteristics in cone-jet and multi-jet modes

As a promising cooling technology, electrospray (ES) cooling has received increasing attention for its efficient thermal-dissipation capability and low coolant requirement. Previous investigations primarily focused on the ES cooling in single ES mode with solitary coolant. Here, we experimentally investigate the spray cooling performances in four ES modes and the effects of two coolants on ES heat transfer. Results show that smaller droplet size, higher speed and larger ES cone angle are observed in cone-jet and multi-jet modes, which are responsible for 32% and 74% of increments of heatflux compared to micro-droplet mode. Moreover, the widest nucleate-boiling zone is attained in multi-jet mode. Increasing coolant volume flux improves ES cooling performance due to the higher velocity and smaller droplet size. Ethylene glycol obtains better ES cooling performance than ethanol, except for at lower wall temperature with the same volume flux. In micro-droplet mode, the droplet bounced by the gas film connects with the fluid at nozzle outlet to form an oscillating liquid column, resulting in fluctuation of wall temperature. When the applied voltage is 3.7 kV and the wall temperature exceeds 110 °C, the ES switches randomly between cone-jet and multi-jet modes at nozzle outlet.