Evaporation Characteristics Of Droplets On The Surface Of Superhydrophobic Fins In The Early Frost Period

Compared with the traditional heating method,the air source heat pump has many advantages such as energy and heat balance,environmental protection and energy saving,and easy installation.However,the air source heat pump is prone to frost in winter.The problem of reduced heat supply and other issues,how to solve the frost problem has become a research hotspot in the field of air source heat pumps.The frosting process on superhydrophobic surfaces can be roughly divided into droplet condensation,droplet freezing,frost crystal growth and expansion,etc.Based on the superhydrophobic fin surface,this paper uses a combination of theory and visual experiments to describe the stage of condensation droplets in the initial stage of frost on superhydrophobic surface,revealing the characteristics of droplet growth,droplet merging and distribution.Although the superhydrophobic surface can delay frost to a certain extent,it cannot completely prevent the growth of the frost layer.Based on the characteristic that the superhydrophobic surface will form condensed droplets at the beginning of frosting,the removal of condensed droplets at the beginning of frosting by hot air heating and evaporation can block its frosting process.The evaporation process is the key link.The mathematical model of droplet evaporation under the action of airflow was established,and the influence of different factors on the evaporation rate of droplets was studied.The microscopic morphological changes during droplet evaporation were experimentally observed to remove condensed droplets in the early frost period.Highly effective frost suppression provides the basis.The specific research content and results are as follows.The droplet growth and distribution characteristics of the superhydrophobic surface during the initial frost period were studied.The layer model of droplet growth in the early frosting stage is established,and the proportion of temperature difference in each layer to the undercooling degree of substrate is obtained.The influence of surface contact angle,area fraction,substrate temperature and relative humidity of air on droplet growth is studied,and the reason is revealed.In this paper,the condensation process of the droplets on the superhydrophobic surface with a contact angle of 151 ° is studied visually,the density distribution characteristics of the droplets at different times are obtained,and the average size and surface coverage of the droplets on the fin surface at different times are studied.The theoretical analysis of the droplet combined bounce process that affects the droplet density distribution is carried out,and the relevant factors that affect the droplet Combined bounce are revealed.A mathematical model of micro-scale single droplet evaporation under the action of airflow was established,and the effects of operating parameters such as droplet radius,substrate temperature,hot airflow temperature,hot airflow velocity,and ambient air relative humidity on the droplet evaporation process were studied.In addition,the effect of surface characteristic parameters such as area fraction and surface contact angle on the droplet evaporation process was explored.The microscopic morphological changes of the droplets during the evaporation process were experimentally observed.The evaporation mode of droplets under different airflow temperatures and velocities was revealed,and the variation rules of the diameter,contact angle and droplet height of the droplets in contact with the fin surface during evaporation were obtained.The energy consumption of droplet evaporation process under the action of different parameters of airflow was carried out,and the airflow temperature,airflow speed and fin surface contact angle were obtained for the evaporation time,total air volume,heat required to heat the air,and fan The influence law of power consumption and total power consumption.A parameter optimization strategy during droplet evaporation is proposed to provide guidance for the evaporation of droplets on the surface of superhydrophobic fins in the initial frost period based on the effect of airflow.