Direct Numerical Simulation of the Microscale Fluid Flow and Heat Transfer in the Three-Phase Contact Line Region During Evaporation

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Stefan Batzdorf ◽  
Tatiana Gambaryan-Roisman ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Contact Line ◽  
Thin Liquid Film ◽  
Contact Angles ◽  
Length Scale ◽  
Phase Contact ◽  
Flow And Heat Transfer ◽  
Three Phase

The heat and mass transfer close to the apparent three-phase contact line is of tremendous importance in many evaporation processes. Despite the extremely small dimensions of this region referred to as the microregion compared to the macroscopic length scale of a boiling process, a considerable fraction of heat can be transferred in this region. Due to its small characteristic length scale, physical phenomena are relevant in the microregion, which are completely negligible on the macroscopic scale, including the action of adhesion forces and the interfacial heat resistance. In the past, models have been developed taking these effects into account. However, so far these models are based on the assumption of one-dimensional (1D) heat conduction, and the flow within the thin liquid film forming the microregion near the apparent three-phase contact line is modeled utilizing the lubrication approximation. Hence, the application of existing models is restricted to small apparent contact angles. Moreover, the effects of surface structures or roughness are not included in these lubrication models. To overcome these limitations, a direct numerical simulation (DNS) of the liquid flow and heat transfer within the microregion is presented in this paper. The DNS is employed for validation of the existing lubrication model and for investigation of the influence of surface nanostructures on the apparent contact angle and in particular on the heat transfer within the microregion.

Numerical Simulation of Digital Microfluidics Based on Electro-Dynamic Model

2012 ◽  
Vol 2 (3) ◽  
pp. 14-23
Author(s):  
Liguo Chen ◽  
Mingxiang Ling ◽  
Deli Liu
Keyword(s):  
Numerical Simulation ◽  
Simulation Model ◽  
Contact Line ◽  
Contact Area ◽  
Digital Microfluidics ◽  
Phase Contact ◽  
Electrowetting On Dielectric ◽  
Three Phase ◽  
Internal Mechanism ◽  
Contact Domain

Aiming at the doubt and divarication about the internal mechanism of electrowetting on dielectric (EWOD) in digital microfluidics, the authors attempted to explain the internal mechanism of EWOD through electro-dynamic-based numerical simulation model. First, the boundary conditions for the governing equation were found. Then the influence of mesh number on simulation results was analyzed and feasibility of the simulation model was verified by comparing numerical results with theoretical ratiocination. Finally, they compared the electro-dynamic actuation force acting on the surface of droplet on three digital microfluidic structures, which have the same three-phase contact line but different area of contact domain. Analytical results showed that electro-dynamic force generated solely by the accumulation of induced charges in contact domain was three times larger than that generated by three-phase contact line. Induced charges accumulated on both three-phase contact line and contact area of droplet gave the contribution to EWOD, but contact area played a major role in the change of contact angle of droplet.

Effect of Three-Phase Contact Line Topology on Dynamic Contact Angles on Heterogeneous Surfaces

Langmuir ◽  
2007 ◽  
Vol 23 (23) ◽  
pp. 11673-11676 ◽  
Author(s):  
Neeharika Anantharaju ◽  
Mahesh V. Panchagnula ◽  
Srikanth Vedantam ◽  
Sudhakar Neti ◽  
Svetlana Tatic-Lucic
Keyword(s):  
Contact Line ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Heterogeneous Surfaces ◽  
Phase Contact ◽  
Three Phase

Spray Cooling Using Multiple Nozzles: Visualization and Wall Heat Transfer Measurements

Volume 3 ◽  
2004 ◽  
Author(s):  
Bohumil Horacek ◽  
Jungho Kim ◽  
Kenneth T. Kiger
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
Heated Surface ◽  
Spray Cooling ◽  
Line Length ◽  
Strongly Correlated ◽  
Phase Contact ◽  
Three Phase ◽  
Phase Change Heat Transfer ◽  
Total Internal Reflectance

Time and space resolved heat transfer data on a nominally isothermal surface cooled by two spray nozzles was obtained using an array of individually controlled microheaters. Visualization and measurements of the liquid-solid contact area and three-phase contact line length were made using a total internal reflectance technique. The spacing between the nozzles and the heated surface was varied between 7 mm and 17 mm. Little interaction between the two sprays was observed for the tested conditions, with the heat flux produced by a single nozzle remaining comparable to that produced by two nozzles, provided the areas considered were limited to the regions impacted by the sprays. Variations in the heat transfer across the surface, however, increased significantly with decreasing spacing. The phase change heat transfer was strongly correlated with the length of the three-phase contact line.

The Impact of Bubble Dynamic Behaviors on Liquid Film in Open Capillary Microgrooves

2011 ◽  
Author(s):  
Yang Cao ◽  
Xuegong Hu ◽  
Dawei Tang ◽  
Chaohong Guo ◽  
Xuelei Nie
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Contact Line ◽  
Thin Liquid Film ◽  
Maximum Speed ◽  
Phase Contact ◽  
Bubble Dynamic ◽  
Dynamic Behaviors ◽  
Liquid Drops ◽  
The Impact

In this paper, the characteristics of bubble dynamic behaviors and the impacts on the triple-phase contact line are studied by a visualization investigation. A high-speed digital camera with maximum speed of 30000 frames per second is adopted to record the period of bubble growth and the geometry of the splashed liquid drops. The information of the bubble dynamic behavior and the liquid drops volume can be analyzed through the software MATLAB. The statistics of the splashed liquid drops is adopted under different heat flux conditions. The experimental results show that the bubble dynamic behaviors lead to the fluctuation of the triple-phase contact line and the splashed liquid drops make the heat transfer capability of the film in microgrooves less than its theoretical maximum value. The investigation indicates that the bubble behaviors can influence the performance of heat transfer through the fluctuations of the triple-phase contact line in the thin liquid film in microgrooves. And the splashed liquid drops appearing in boiling process can also affect the heat transfer of the liquid film in open capillary microgrooves.

Sign in / Sign up

Export Citation Format

Share Document