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Research Papers: Micro/Nanoscale Heat Transfer

Droplet Heat Transfer on Micropost Arrays With Hydrophobic and Hydrophilic Characteristics

[+] Author and Article Information
Abdullah Al-Sharafi

Department of Mechanical Engineering,
King Fahd University of
Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: alsharafi@kfupm.edu.sa

Bekir S. Yilbas

Department of Mechanical Engineering &
Centre of Excellence for Renewable Energy,
King Fahd University of
Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: bsyilbas@kfupm.edu.sa

Haider Ali

Department of Mechanical Engineering,
King Fahd University of
Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: haiali@kfupm.edu.sa

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received April 17, 2017; final manuscript received January 3, 2018; published online April 6, 2018. Assoc. Editor: Gennady Ziskind.

J. Heat Transfer 140(7), 072402 (Apr 06, 2018) (17 pages) Paper No: HT-17-1217; doi: 10.1115/1.4039013 History: Received April 17, 2017; Revised January 03, 2018

Heat transfer analysis for a water droplet on micropost arrays is carried out while mimicking the environmental conditions. Since the micropost arrays spacing size alters the state of the hydrophilicity of the surface, the size of the micropost arrays spacing is varied and the resulting heat transfer characteristics are analyzed. Spreading rate of water droplet on the micropost arrays is considered and the adhesion force for the pinning of the water droplet on the micropost arrays is presented. Temperature and flow fields are predicted and the predictions of flow velocity inside the water droplet are validated through the particle image velocimetry (PIV). The Nusselt number variation for various sizes of the micropost arrays is obtained for two droplet volumes. It is found that reducing the solid fraction of micropost array beyond ϕs = 0.25, the Cassie and Baxter state of the surface changes to the Wenzel state; in which case, hydrophobic characteristics changes to hydrophilic characteristics for the water droplet. Heat transfer from the droplet bottom gives rise to development of the buoyancy and the Marangoni currents, which in turn generate two counter rotating circulation cells. The center of circulation cells moves further in the droplet upper part for the hydrophobic droplet case. The Nusselt number attains high values for the hydrophobic droplet at micropost array spacing size b = 10 μm and hydrophobic droplet at spacing size b = 50 μm due to fin effects of the micropost arrays.

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References

Quan, Y.-Y. , Zhang, L.-Z. , Qi, R.-H. , and Cai, R.-R. , 2016, “ Self-Cleaning of Surfaces: The Role of Surface Wettability and Dust Types,” Sci. Rep., 6, p. 38239. [CrossRef] [PubMed]
Han, J. T. , Xu, X. , and Cho, K. , 2005, “ Diverse Access to Artificial Superhydrophobic Surfaces Using Block Copolymers,” Langmuir, 21(15), pp. 6662–6665. [CrossRef] [PubMed]
Shirtcliffe, N. J. , McHale, G. , Newton, M. I. , Chabrol, G. , and Perry, C. C. , 2004, “ Dual‐Scale Roughness Produces Unusually Water‐Repellent Surfaces,” Adv. Mater., 16(21), pp. 1929–1932. [CrossRef]
Kinoshita, H. , Ogasahara, A. , Fukuda, Y. , and Ohmae, N. , 2010, “ Superhydrophobic/Superhydrophilic Micropatterning on a Carbon Nanotube Film Using a Laser Plasma-Type Hyperthermal Atom Beam Facility,” Carbon, 48(15), pp. 4403–4408. [CrossRef]
Latthe, S. S. , Imai, H. , Ganesan, V. , and Rao, A. V. , 2009, “ Superhydrophobic Silica Films by Sol–Gel Co-Precursor Method,” Appl. Surf. Sci., 256(1), pp. 217–222. [CrossRef]
Ma, M. , Mao, Y. , Gupta, M. , Gleason, K. K. , and Rutledge, G. C. , 2005, “ Superhydrophobic Fabrics Produced by Electrospinning and Chemical Vapor Deposition,” Macromolecules, 38(23), pp. 9742–9748. [CrossRef]
Yilbas, B. , Khaled, M. , Abu-Dheir, N. , Al-Aqeeli, N. , Said, S. , Ahmed, A. , Varanasi, K. , and Toumi, Y. , 2014, “ Wetting and Other Physical Characteristics of Polycarbonate Surface Textured Using Laser Ablation,” Appl. Surf. Sci., 320, pp. 21–29. [CrossRef]
Zhang, X. , Guo, Y. , Zhang, P. , Wu, Z. , and Zhang, Z. , 2010, “ Superhydrophobic CuO@Cu2S Nanoplate Vertical Arrays on Copper Surfaces,” Mater. Lett., 64(10), pp. 1200–1203. [CrossRef]
Liu, J. , Ashmkhan, M. , Dong, G. , Wang, B. , and Yi, F. , 2013, “ Fabrication of Micro-Nano Surface Texture by CsCl Lithography With Antireflection and Photoelectronic Properties for Solar Cells,” Sol. Energy Mater. Sol. Cells, 108, pp. 93–97. [CrossRef]
Samuel, B. , Zhao, H. , and Law, K.-Y. , 2011, “ Study of Wetting and Adhesion Interactions Between Water and Various Polymer and Superhydrophobic Surfaces,” J. Phys. Chem. C, 115(30), pp. 14852–14861. [CrossRef]
Zhang, T. , Alvarado, J. L. , Muthusamy, J. , Kanjirakat, A. , and Sadr, R. , 2017, “ Heat Transfer Characteristics of Double, Triple and Hexagonally-Arranged Droplet Train Impingement Arrays,” Int. J. Heat Mass Transfer, 110, pp. 562–575. [CrossRef]
Zubkov, V. , Cossali, G. , Tonini, S. , Rybdylova, O. , Crua, C. , Heikal, M. , and Sazhin, S. , 2017, “ Mathematical Modelling of Heating and Evaporation of a Spheroidal Droplet,” Int. J. Heat Mass Transfer, 108(Pt. B), pp. 2181–2190. [CrossRef]
Al-Sharafi, A. , Yilbas, B. S. , Sahin, A. Z. , Ali, H. , and Al-Qahtani, H. , 2016, “ Heat Transfer Characteristics and Internal Fluidity of a Sessile Droplet on Hydrophilic and Hydrophobic Surfaces,” Appl. Therm. Eng., 108, pp. 628–640. [CrossRef]
Moon, J. H. , Cho, M. , and Lee, S. H. , 2016, “ Dynamic Wetting and Heat Transfer Characteristics of a Liquid Droplet Impinging on Heated Textured Surfaces,” Int. J. Heat Mass Transfer, 97, pp. 308–317. [CrossRef]
Jung, J. , Jeong, S. , and Kim, H. , 2016, “ Investigation of Single-Droplet/Wall Collision Heat Transfer Characteristics Using Infrared Thermometry,” Int. J. Heat Mass Transfer, 92, pp. 774–783. [CrossRef]
Wang, Z. , Xing, Y. , Liu, X. , Zhao, L. , and Ji, Y. , 2016, “ Computer Modeling of Droplets Impact on Heat Transfer During Spray Cooling Under Vibration Environment,” Appl. Therm. Eng., 107, pp. 453–462. [CrossRef]
Hays, R. , Maynes, D. , and Crockett, J. , 2016, “ Thermal Transport to Droplets on Heated Superhydrophobic Substrates,” Int. J. Heat Mass Transfer, 98, pp. 70–80. [CrossRef]
Venkatesan, J. , Rajasekaran, S. , Das, A. , and Ganesan, S. , 2016, “ Effects of Temperature-Dependent Contact Angle on the Flow Dynamics of an Impinging Droplet on a Hot Solid Substrate,” Int. J. Heat Fluid Flow, 62(Pt. B), pp. 282–298. [CrossRef]
Yang, Z. , Ma, X.-C. , Duan, Y.-Y. , and Chen, Y. , 2013, “ Internal Flow and Heat Transfer of a Condensing Water Droplet in Steam Flow,” Chem. Eng. Sci., 94, pp. 54–59. [CrossRef]
Clavijo, C. E. , Crockett, J. , and Maynes, D. , 2017, “ Hydrodynamics of Droplet Impingement on Hot Surfaces of Varying Wettability,” Int. J. Heat Mass Transfer, 108(Pt. B), pp. 1714–1726. [CrossRef]
Zheng, Z. , Zhou, L. , Du, X. , and Yang, Y. , 2016, “ Numerical Investigation on Conjugate Heat Transfer of Evaporating Thin Film in a Sessile Droplet,” Int. J. Heat Mass Transfer, 101, pp. 10–19. [CrossRef]
Al-Sharafi, A. , Yilbas, B. S. , Sahin, A. Z. , and Ali, H. , 2017, “ Flow Field Inside a Sessile Droplet on a Hydrophobic Surface in Relation to Self-Cleaning Applications of Dust Particles,” ASME J. Heat Transfer, 139(4), p. 042003. [CrossRef]
Al-Sharafi, A. , Yilbas, B. S. , Ali, H. , and Sahin, A. Z. , 2016, “ Internal Fluidity of a Sessile Droplet With the Presence of Particles on a Hydrophobic Surface,” Numer. Heat Transfer, Part A: Appl., 70(10), pp. 1118–1140. [CrossRef]
Mahadevan, L. , and Pomeau, Y. , 1999, “ Rolling Droplets,” Phys. Fluids, 11(9), pp. 2449–2453. [CrossRef]
Tam, D. , von Arnim, V. , McKinley, G. , and Hosoi, A. , 2009, “ Marangoni Convection in Droplets on Superhydrophobic Surfaces,” J. Fluid Mech., 624, pp. 101–123. [CrossRef]
Lu, G. , Duan, Y.-Y. , Wang, X.-D. , and Lee, D.-J. , 2011, “ Internal Flow in Evaporating Droplet on Heated Solid Surface,” Int. J. Heat Mass Transfer, 54(19), pp. 4437–4447. [CrossRef]
COMSOL, 2017, “COMSOL,” COMSOL Inc., Burlington, MA, accessed Jan. 24, 2018, http://www.comsol.com/comsol-multiphysics
Mackenzie, J. , and Mekwi, W. , 2012, “ An Unconditionally Stable Second-Order Accurate ALE–FEM Scheme for Two-Dimensional Convection–Diffusion Problems,” IMA J. Numer. Anal., 32(3), pp. 888–905. [CrossRef]
Zografos, A. I. , Martin, W. A. , and Sunderland, J. E. , 1987, “ Equations of Properties as a Function of Temperature for Seven Fluids,” Comput. Methods Appl. Mech. Eng., 61(2), pp. 177–187. [CrossRef]
Al-Sharafi, A. , Yilbas, B. S. , and Ali, H. , 2017, “ Heat Transfer and Fluid Flow Characteristics in a Sessile Droplet on Oil-Impregnated Surface Under Thermal Disturbance,” ASME J. Heat Transfer, 139(9), p. 092004.
Ismail, A. , Grest, G. S. , Stevens, M. J. , Heine, D. R. , and Tsige, M. , 2017, “Interfacial Properties of PDMS-Water Systems,” Sandia National Laboratory, Albuquerque, NM, accessed Jan. 24, 2017, https://www.osti.gov/scitech/servlets/purl/1264508
Smith, J. D. , Dhiman, R. , Anand, S. , Reza-Garduno, E. , Cohen, R. E. , McKinley, G. H. , and Varanasi, K. K. , 2013, “ Droplet Mobility on Lubricant-Impregnated Surfaces,” Soft Matter, 9(6), pp. 1772–1780. [CrossRef]
Bhushan, B. , and Nosonovsky, M. , 2010, “ The Rose Petal Effect and the Modes of Superhydrophobicity,” Philos. Trans. R. Soc. London A: Math., Phys. Eng. Sci., 368(1929), pp. 4713–4728. [CrossRef]
Bhushan, B. , and Jung, Y. C. , 2008, “ Wetting, Adhesion and Friction of Superhydrophobic and Hydrophilic Leaves and Fabricated Micro/Nanopatterned Surfaces,” J. Phys.: Condens. Matter, 20(22), p. 225010. [CrossRef]
Pilat, D. , Papadopoulos, P. , Schaffel, D. , Vollmer, D. , Berger, R. , and Butt, H.-J. , 2012, “ Dynamic Measurement of the Force Required to Move a Liquid Drop on a Solid Surface,” Langmuir, 28(49), pp. 16812–16820. [CrossRef] [PubMed]
Ayyad, A. H. , 2010, “ Thermodynamic Derivation of the Young–Dupré Form Equations for the Case of Two Immiscible Liquid Drops Resting on a Solid Substrate,” J. Colloid Interface Sci., 346(2), pp. 483–485. [CrossRef] [PubMed]
Smythe, W. R. , 1968, Static and Dynamic Electricity, 3rd ed., McGraw-Hill, New York.
Yovanovich, M. , and Marotta, E. , 2003, “ Thermal Spreading and Contact Resistances,” Handbook of Heat Transfer, A. Bejan , and A. D. Kraus , eds., Wiley, Hoboken, NJ, pp. 261–394.
Lam, L. S. , Hodes, M. , and Enright, R. , 2015, “ Analysis of Galinstan-Based Microgap Cooling Enhancement Using Structured Surfaces,” ASME J. Heat Transfer, 137(9), p. 091003. [CrossRef]
Lam, L. S. , Hodes, M. , Karamanis, G. , Kirk, T. , and MacLachlan, S. , 2016, “ Effect of Meniscus Curvature on Apparent Thermal Slip,” ASME J. Heat Transfer, 138(12), p. 122004. [CrossRef]

Figures

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Fig. 1

Scanning electron microscopy micrographs of micropost arrays surface (a is the micropost width, b is micropost arrays spacing size, and h is the micropost height): (a) micropost arrays with a = b = h = 10 μm, (b) micropost arrays with a = h = 10 μm and b = 25 μm, (c) micropost arrays with a = h = 10 μm and b = 50 μm, and (d) micropost

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Fig. 2

Optical images of the water droplet located on: (a) micropost arrays with a = b = h = 10 μm, (b) micropost arrays with a = h = 10 μm and b = 25 μm, and (c) micropost arrays with a = h = 10 μm and b = 50 μm

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Fig. 3

Mesh used in the simulations for two different micropost arrays spacing sizes and droplet volume of 60 μL. b = 50 μm results in hydrophobic droplet state where water impregnates into micropost arrays, and b = 10 μm gives rise to hydrophobic droplet state where air gap is present within the micropost arrays spacing

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Fig. 4

Grid-independent solution for velocity and temperature for 60 μL droplet: (a) velocity variation along the central rake for various grid sizes and (b) temperature variation along the central rake for various grid sizes

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Fig. 5

Two-dimensional and 3D solutions for velocity field (m/s) for 60 μL droplet and b = 50 μm: (a) 2D velocity field and (b) 3D velocity field

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Fig. 6

Contact angle of water droplets on plane and micropost arrays of Polydimethylsiloxane PDMS surface

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Fig. 7

Image of hollow glass particles obtained from PIV and velocity simulations for 40 μL droplet: (a) hollow glass particles inside droplet at different durations and (b) trajectory of hollow glass particles and corresponding velocity contours. Each frame of PIV images is represented at 300 milliseconds during the heating period.

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Fig. 8

(a) Water droplet puddle height to width ratio (ϕs=(Asoild/AProjected)=(a2/(a+b)2)), and (b) droplet contact angles predicted and obtained from experiments for various values of micropost arrays spacing sizes

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Fig. 9

Adhesion force of 7 μL water droplet on micropost arrays with various sizes micropost array spacing

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Fig. 10

Velocity and temperature variations along the central rake for various heating durations: (a) velocity variation and (b) temperature variation

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Fig. 11

(a) Water droplet images and velocity contours (m/s) inside the droplet for various micropost arrays spacing (b) and 20 μL droplet volume and (b) water droplet images and velocity contours (m/s) inside the droplet for various micropost arrays spacing (b) and 60 μL droplet volume

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Fig. 12

Temperature contours inside the droplet for micropost arrays spacing b = 10, b = 25, and b = 50 μm and various droplet volumes

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Fig. 13

Velocity and temperature variation along horizontal rake extending top of micropost arrays surface for b = 50 μm and droplet volume 60 μL: (a) velocity variation and (b) temperature variation

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Fig. 14

Temperature variation (K) within the spacing of micropost arrays of b = 50 μm and droplet volume of 60 μL: (a) temperature profiles and (b) temperature contours for two heating durations

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Fig. 15

Thermal spreading resistance variation with the fraction of the projected area of the micropost array surface, which is occupied by the solid (ϕs=(Asoild/AProjected)=(a2/(a+b)2)) for two droplet volumes

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Fig. 16

Nusselt number variation with the fraction of the projected area of the micropost array surface, which is occupied by the solid (ϕs=(Asoild/AProjected)=(a2/(a+b)2)) for two droplet volumes

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Fig. 17

A micropost arrays and geometric configurations

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Fig. 18

A schematic view of micropost arrays spacing and bulging droplet, with radius R, in between the microposts with small micropost arrays spacing length

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Fig. 19

A schematic view of micropost array spacing and bulging droplet, with radius R, in between the microposts with large micropost array spacing length

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Fig. 20

A schematic view of ray-tracing diagram for a spherical liquid lens [26]

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