结霜初期超疏水表面凝结液滴的自跳跃脱落及其对结霜过程的影响

Jumping of condensation droplets on superhydrophobic surfaces at early frosting stage and its effects on frost formation

制备了具有微纳复合结构的超疏水表面,对其结霜过程进行了可视化观测,揭示了结霜初期表面凝结液滴的自跳跃行为及其对结霜过程的影响,并与普通表面的结霜过程进行了对比研究.实验结果表明,结霜初期,超疏水表面的凝结液滴频繁出现合并后自跳跃现象,根据液滴合并前的尺寸大小,可将自跳跃行为分为3类,而普通表面未观察到类似现象;液滴自跳跃临界半径随着液固接触面积分数的降低和表面接触角的增大而减小.初始凝结液滴的自跳跃降低了超疏水表面液滴覆盖率和分布密度,同时引起表面霜层生长的不均匀性和霜晶结构的差异.与普通表面相比,超疏水表面可有效抑制结霜,延缓霜层生长速率.

A superhydrophobic surface with micro-nano structure was prepared and the visualization was carried out to study its frost formation. The jumping of condensation droplets on superhydrophobic surface at early frosting stage and its effects on the frost formation were revealed and compared with those of bare surfaces. Experimental results showthat the jumping behaviors of the condensation droplets frequently appear on the superhydrophobic surface at early frosting stage. The behavtors can be divided into three types according to the sizes of the droplets before the coalescence,while there is no jumping behavior on the bare surface. The jumping critical radius decreases with the increase of the surface contact angle and the decrease of the solid-liquid contact area. Jumping of condensate droplets can reduce the droplet distribution density and surface covered fraction,and result in the unevenness of frost layer and difference in frost crystals. Compared with the bare surface,the superhydrophobic surface can effectively restrain the frost formation and delay the growth rate of the frost layer.