Dropwise Condensation on Hydrophobic Horizontal Tube:Droplet Departure Characteristics in Subregion
Dropwise condensation can improve the efficiency of condenser in power generation sys-tem and the droplet dynamic behavior is closely related to the heat transfer process.It is significant to clarify the droplet dynamic behavior for condenser design.In this work,the PFA hydrophobic coating is used to modify the copper tube,and the contact angle in the air is 142.6°,which could achieve stable dropwise condensation.Different from the droplet departure process on vertical wall,the gravity component acting on the droplet is related to the circumferential angle of the horizontal tube,then the droplet departure sizes along the circumferential direction of the horizontal tube show discrepancy.Based on this,the surface of the horizontal tube is divided into two regions,and two droplet sweeping modes'local sweeping'and'complete sweeping'are proposed.The differences of departure position and time sequence cause a higher surface renewal rate at the lower region,the droplet number density of the lower part is slightly higher than that of the upper part within droplet size range of r＜400 μm.The local sweeping can limit the droplet size in the lower region and reduce the droplet coverage area.
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NSTL
万方数据
维普
