Dynamic Characteristics Of Droplet Impinging And Evaporation On The Wall

With the development of heat transfer technology,the application of spray cooling technology is more and more extensive in practice.Therefore,how to correctly understand the impact and evaporation behavior of atomized droplets on various heat exchangers,and scientifically and accurately describe the physical process of droplet impact and evaporation,are helpful to understand the process and rationale of heat and mass transfer enhancement.At present,the research on liquid impingement and evaporation is lack of systematicness and comprehensiveness,and little attention has been paid to the transient heating process and the dynamic mechanism of solid evaporation of liquid drop impingement.In this paper,the following aspects have been studied for these problems:(1)GLSVOF model is used to study the transient process of droplet impinging on the hot wall.The characteristics of phase,internal flow field,pressure field and temperature field at different times in the process of single droplet impinging on the hot wall are analyzed in detail.(2)The effects of wall temperature,initial velocity,diameter and contact angle on droplet spreading and heat transfer process were compared and analyzed by means of numerical simulation.The trends of droplet spreading coefficient and heat flux density were obtained when the above parameters changed.The effects of bubble,three line contact point and field synergy principle on wall heat transfer are discussed.(3)The effects of wall temperature and initial volume of droplets on initial contact angle,contact angle,contact diameter and evaporation time were analyzed.The results show that: the initial contact angle of the droplet changes with the change of parameters;the wall temperature is negatively correlated with the contact angle and evaporation time,and positively correlated with the contact diameter;the initial volume of the droplet is positively correlated with the contact diameter and evaporation time,and negatively correlated with the contact angle.the 2 / 3 power of the droplet volume is linearly related to the evaporation time.(4)Based on the VOF model,the evaporation process of a single droplet on the hot wall is simulated.The flow field,temperature field and pressure field in the boiling region x at different times are studied in detail.Based on the experimental results,the difference between the evaporation process in the non boiling region and the boiling evaporation process is analyzed.The concept of the critical contact diameter of the solid droplet evaporation in the transition state on the rough wall is proposed.The temperature range of the solid droplet evaporation mode on the aluminum plate is 93.2 ～ 100 Celsius degree.