Theoretical Study of Dropwise Condensation Heat Transfer: Effect of the Liquid-Solid Surface Free Energy Difference

2009 ◽  
Vol 16 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Zhong Lan ◽  
Xue-Hu Ma ◽  
Xing-Dong Zhou ◽  
Mingzhe Wang
Keyword(s):  
Heat Transfer ◽  
Free Energy ◽  
Surface Free Energy ◽  
Solid Surface ◽  
Theoretical Study ◽  
Energy Difference ◽  
Transfer Effect ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Free Energy Difference

Effect of Surface-Free-Energy-Difference on Condensation Characteristic Curves of Binary Mixture of Steam and Ethanol Vapor

2006 ◽  
Author(s):  
Xue-Hu Ma ◽  
Zhong Lan ◽  
Xing-Dong Zhou ◽  
Yu Zhang
Keyword(s):  
Heat Transfer ◽  
Free Energy ◽  
Binary Mixture ◽  
Surface Free Energy ◽  
Ethanol Vapor ◽  
Energy Difference ◽  
Heat Transfer Process ◽  
Condensation Heat Transfer ◽  
Free Energy Difference ◽  
Operation Conditions

The condensation heat transfer process of binary mixture of steam and ethanol vapor was studied experimentally with various ethanol concentrations and surface subcooling at atmospheric pressure. The experiments demonstrate that the condensation modes alter from filmwise, to transition and finally to dropwise with respect to the operation conditions. The marangoni effect was always used to interpret this phenomenon in the published literature. In this paper, the mechanism of condensation heat transfer with the liquid-solid-surface-free-energy-difference is used to further understand this process and the conversion of condensation modes. From this viewpoint, the condensation characteristics of binary mixture of steam and ethanol vapor can be explained reasonably with the corresponding condensation modes. Base on the data of the present paper and those reported in literature, the conversion criterion of the condensation modes is proposed. The condensation state is filmwise for the surface-free-energy-difference less than 14±1 mJ·m−2 and dropwise for more than 21±1 mJ·m−2 and transition for between 14±1 mJ·m−2 and 21±1 mJ·m−2.

Dropwise Condensation Heat Transfer Model: Effect of the Liquid-Solid Surface Free Energy Difference

2006 ◽  
Author(s):  
Xue-Hu Ma ◽  
Zhong Lan ◽  
Yu Zhang ◽  
Xing-Dong Zhou ◽  
Tian-Yi Sun
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Free Energy ◽  
Heat Transfer Coefficient ◽  
Energy Difference ◽  
Interfacial Interaction ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Free Energy Difference ◽  
Simulation Results

Dropwise condensation heat transfer performance depends not only on the condensing conditions, but also on the interfacial interaction between condensate and condensing surface material. Based on the well-established Rose’s model, a modified model of dropwise condensation heat transfer is proposed by considering the interfacial interaction between liquid and solid, and established by rebuilding the space conformation of drop distributing into time conformation. The simulation results indicate that the heat transfer coefficient increases with the surface free energy difference increasing and the contact angle hysteresis decreasing. The larger contact angle and the smaller departure drop size result in the higher heat transfer coefficient. Different interfacial effect gives rise to the different heat transfer curves. For the identical solid-liquid-vapor system, the simulation results agree very well with the present experimental data and those reported in literature. The controversy among experimental results in literature might be well understood with the concept of the present paper.

A Heat Transfer Model of Dropwise Condensation Underneath a Horizontal Substrate

2011 ◽  
Vol 199-200 ◽  
pp. 1604-1608
Author(s):  
Yun Fu Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Fractal Model ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Transfer Model ◽  
Dropwise Condensation ◽  
Small Contact Angle ◽  
Horizontal Substrate

For finding influence of the condensing surface to dropwise condensation heat transfer, a fractal model for dropwise condensation heat transfer has been established based on the self-similarity characteristics of droplet growth at various magnifications on condensing surfaces with considering influence of contact angle to heat transfer. It has been shown based on the proposed fractal model that the area fraction of drops decreases with contact angle increase under the same sub-cooled temperature; Varying the contact angle changes the drop distribution; higher the contact angle, lower the departing droplet size and large number density of small droplets; dropwise condensation translates easily to the filmwise condensation at the small contact angle ;the heat flux increases with the sub-cooled temperature increases, and the greater of contact angle, the more heat flux increases slowly.

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