Wettability, Spreading And Heat Transfer Characteristics Of Droplet On A Heated Solid Surface

The spreading process of droplet on solid surface can be driven and controlled by changing external conditions,such as the application of temperature gradient,adding surfactant and so on,this control technology plays a crucial role in coating,printing,oil extracting,mineral flotating,film manufacturing,preparation of magnetic fluid material and medical fields.In addition,the spreading characteristics of the droplet on solid surface will affect the heat transfer process,and it has important significance for the design of good liquid cooling system,ensuring the normal operation of related electronic and aerospace equipments and prolonging their service life?The above problem is very complicated,involving the variation of contact angle,the travelling of three-phase contact line,the Marangoni effect,the heat transfer process between droplet and substrate and other aspects,but because of its wide application and potential developing prospect,it is necessary to carry out related research?Therefore,the influencing factors of wettability,spreading and heat transfer characteristics of droplet on heated solid surface are discussed in the present paper,by the combination of theoretical derivation and numerical simulation,and the main contents are as follows:(1)The evolution model of a droplet on heated solid substrate is established,based on the lubrication theory,and the influence of the wall temperature on the wettability and droplet spreading is examined from the point view of equilibrium contact angle?Furthermore,characteristics of the variation of contact angle,the travelling speed of contact line,and the spreading range of droplet are compared when the sensitivity of the liquid-solid,liquid-gas and solid-gas interfacial tensions to temperature changes;(2)The spreading processes of droplet on heated solid surface are simulated under different wall temperature distribution?The reason why the single-peak feature of the droplet thickness profile gradually evoluted into a double-peak feature and the peak value increases firstly and then decreases when the wall temperature is uniform and is decreased exponentially from the center to both sides is explained?A method is proposed for calculating the heat flux and heat transfer of two-dimensional liquid droplet?The influence of spreading characteristic and heat convective condition at the liquid-gas interface on heat transfer features of the droplet is examined using that method.