Boiling evaporation characteristics of sessile droplets and its transition evaporation mode

Abstract Providing an enormous heat transfer, droplet boiling evaporation is widely used in the liquid cooling for nucleate reactors and high-power electronic devices and other fields. This paper reported a combined theoretical and experimental study on the evaporation characteristics of the droplets attached to a high temperature wall (>100°C). Different from the non-boiling evaporation, the effect of droplet temperature on evaporation time, contact angle and evaporation process are investigated. Nucleate boiling regime in the evaporation of a single droplet, especially the transition from static evaporation to nucleate boiling is investigated. Our results report that the evaporation of sessile droplets in boiling regime is very intense, and can be classified into five stages according to the change in internal bubble morphology, namely the wall bubble germination, wall bubble growth, global bubble germination, global bubble growth, and central large bubble formation. Droplet evaporation does not follow the constant contact diameter pattern in the non-boiling regime, but consists of growth period, steady period, and decline period. Basically consistent with the experimental results, the feasibility of numerical simulation to study the droplet evaporation in the boiling regime is verified.