Research Papers: Micro/Nanoscale Heat Transfer

Tuning Superhydrophilic Nanostructured Surfaces to Maximize Water Droplet Evaporation Heat Transfer Performance

[+] Author and Article Information
Claire K. Wemp

Mechanical Engineering Department,
University of California,
Berkeley, CA 94720-1740
e-mail: ckunkle@berkeley.edu

Van P. Carey

Fellow ASME
Mechanical Engineering Department,
University of California,
6123 Etcheverry Hall,
Berkeley, CA 94720-1740
e-mail: vpcarey@berkeley.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received August 3, 2017; final manuscript received April 20, 2018; published online May 25, 2018. Assoc. Editor: Yuwen Zhang.

J. Heat Transfer 140(10), 102401 (May 25, 2018) (10 pages) Paper No: HT-17-1447; doi: 10.1115/1.4040142 History: Received August 03, 2017; Revised April 20, 2018

Spraying water droplets on air fin surfaces is often used to augment the performance of air-cooled Rankine power plant condensers and wet cooling tower heat exchangers for building air-conditioning systems. To get the best performance in such processes, the water droplets delivered to the surface should spread rapidly into an extensive, thin film and evaporate with no liquid leaving the surface due to recoil or splashing. This paper presents predictions of theoretical/computational modeling and results of experimental studies of droplet spreading on thin-layer, nanostructured, superhydrophilic surfaces that exhibit very high wicking rates (wickability) in the porous layer. Analysis of the experimental data in the model framework illuminates the key aspects of the physics of the droplet-spreading process and evaporation heat transfer. This analysis also predicts the dependence of droplet-spreading characteristics on the nanoporous surface morphology and other system parameters. The combined results of this investigation indicate specific key strategies for design and fabrication of surface coatings that will maximize the heat transfer performance for droplet evaporation on heat exchanger surfaces. The implications regarding wickability effects on pool boiling processes are also discussed.

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Li, C. , Wang, Z. , Wang, P. I. , Peles, Y. , Koratkar, N. , and Peterson, G. P. , 2008, “ Nanostructured Copper Interfaces for Enhanced Boiling,” Small, 4(8), pp. 1084–1088. [CrossRef] [PubMed]
Chen, R. , Lu, M.-C. , Srinivasan, V. , Wang, Z. , Cho, H. H. , and Majumdar, A. , 2009, “ Nanowires for Enhanced Boiling Heat Transfer,” Nano Lett., 9(2), pp. 548–553. [CrossRef] [PubMed]
Sathyamurthi, V. , Ahn, H. S. , Banerjee, D. , and Lau, S. C. , 2009, “ Subcooled Pool Boiling Experiments on Horizontal Heaters Coated With Carbon Nanotubes,” ASME J. Heat Transfer, 131(7), p. 071501. [CrossRef]
Lu, M.-C. , Chen, R. , Srinivasan, V. , Carey, V. P. , and Majumdar, A. , 2011, “ Critical Heat Flux of Pool Boiling on Si Nanowire Array-Coated Surfaces,” Int. J. Heat Mass Transfer, 54(25–26), pp. 5359–5367. [CrossRef]
Yao, Z. , Lu, Y. W. , and Kandlikar, S. G. , 2011, “ Effects of Nanowire Height on Pool Boiling Performance of Water on Silicon Chips,” Int. J. Therm. Sci., 50(11), pp. 2084–2090. [CrossRef]
Rahman, M. M. , Ölcçroğlu, E. , and McCarthy, M. , 2014, “ Scalable Nanomanufacturing of Virus-Templated Coatings for Enhanced Boiling,” Adv. Mater. Interfaces, 1(2), p. 1300107. [CrossRef]
Rahman, M. M. , Ölcçroğlu, E. , and McCarthy, M. , 2014, “ Role of Wickability on the Critical Heat Flux of Structured Superhydrophilic Surfaces,” Langmuir, 30(37), pp. 11225–11234. [CrossRef] [PubMed]
Kim, B. S. , Lee, H. , Shin, S. , Choi, G. , and Cho, H. H. , 2014, “ Interfacial Wicking Dynamics and Its Impact on Critical Heat Flux of Boiling Heat Transfer,” Appl. Phys. Lett., 105(19), p. 191671.
Ahn, H. S. , Park, G. , Kim, J. M. , Kim, J. , and Kim, M. H. , 2012, “ The Effect of Water Absorption on Critical Heat Flux Enhancement During Pool Boiling,” Exp. Therm. Fluid Sci., 42, pp. 187–195. [CrossRef]
Chu, K.-H. , Soo Joung, Y. , Enright, R. , Buie, C. R. , and Wang, E. N. , 2013, “ Hierarchically Structured Surfaces for Boiling Critical Heat Flux Enhancement,” Appl. Phys. Lett., 102(15), p. 151602. [CrossRef]
Kim, S. , Kim, H. D. , Kim, H. , Ahn, H. S. , Jo, H. , Kim, J. , and Kim, M. H. , 2010, “ Effects of Nano-Fluid and Surfaces With Nano Structure on the Increase of CHF,” Exp. Therm. Fluid Sci., 34(4), pp. 487–495. [CrossRef]
Yao, Z. , Lu, Y.-W. , and Kandlikar, S. G. , 2012, “ Pool Boiling Heat Transfer Enhancement Through Nanostructures on Silicon Microchannels,” ASME J. Nanotechnol. Eng. Med., 3(3), p. 031002. [CrossRef]
Bon, B. , Klausner, J. F. , and McKenna, E. , 2013, “ The Hoodoo: A New Surface Structure for Enhanced Boiling Heat Transfer,” ASME J. Therm. Sci. Eng. Appl., 5(1), p. 011003. [CrossRef]
Chu, K.-H. , Enright, R. , and Wang, E. N. , 2012, “ Structured Surfaces for Enhanced Pool Boiling Heat Transfer,” Appl. Phys. Lett., 100(24), p. 241603. [CrossRef]
O'Hanley, H. , Coyle, C. , Buongiorno, J. , McKrell, T. , Hu, L.-W. , Rubner, M. , and Cohen, R. , 2013, “ Separate Effects of Surface Roughness, Wettability, and Porosity on the Boiling Critical Heat Flux,” Appl. Phys. Lett., 103(2), p. 024102. [CrossRef]
Zou, A. , and Maroo, S. C. , 2013, “ Critical Height of Micro/Nano Structures for Pool Boiling Heat Transfer Enhancement,” Appl. Phys. Lett., 103(22), p. 221602. [CrossRef]
Ruiz, M. , Kunkle, C. M. , Padilla , J., Jr. , and Carey, V. P. , 2017, “ Boiling Heat Transfer Performance in a Spiraling Radial Inflow Microchannel Cold Plate,” Heat Transfer Eng., 38(14–15), pp. 1247–1259. [CrossRef]
Padilla, J. , and Carey, V. P. , 2014, “ Water Droplet Vaporization on Superhydrophilic Nanostructured Surfaces at High and Low Superheat,” ASME Paper No. IMECE2014-39957.
Kunkle, C. M. , Mizerak, J. P. , and Carey, V. P. , 2017, “ The Effects of Wettability and Surface Morphology on Heat Transfer for Zinc Oxide Nanostructured Aluminum Surfaces,” ASME Paper No. HT2017-4847.
Xiao, R. , Enright, R. , and Wang, E. N. , 2010, “ Prediction and Optimization of Liquid Propagation in Micropillar Arrays,” Langmuir Lett., 26(19), pp. 15070–15075. [CrossRef]
Zhu, Y. , DiAntao, D. S. , Lu, Z. , Somasundaram, S. , Zhang, T. , and Wang, E. N. , 2016, “ Prediction and Characterization of Dry-Out Heat Flux in Micropillar Wick Structures,” Langmuir, 32(7), pp. 1920–1927. [CrossRef] [PubMed]
Joung, Y. S. , and Buie, C. R. , 2014, “ Scaling Laws for Drop Impingement on Porous Films and Papers,” Phys. Rev. E, 89(1), p. 013015. [CrossRef]
Mitra, S. , and Mitra, S. K. , 2016, “ Understanding the Early Regime of Drop Spreading,” Langmuir, 32(35), pp. 8843–8848. [CrossRef] [PubMed]
Navaz, H. K. , Markicevic, B. , Zand, A. R. , Sikorski, Y. , Chan, E. , Sanders, M. , and D'Onofrio, T. G. , 2008, “ Sessile Droplet Spread Into Porous Substrates—Determination of Capillary Pressure Using a Continuum Approach,” J. Colloid Interface Sci., 325(2), pp. 440–446. [CrossRef] [PubMed]
Reis , N. C., Jr. , Griffiths, R. F. , and Méri Santos, J. , 2008, “ Parametric Study of Liquid Droplets Impinging on Porous Surfaces,” Appl. Math. Modell., 32(3), pp. 341–361. [CrossRef]
Clarke, A. , Blake, T. D. , Carruthers, K. , and Woodward, A. , 2002, “ Spreading and Imbibition of Liquid Droplets on Porous Surfaces,” Langmuir, 18(8), pp. 2980–2984. [CrossRef]
Quéré, D. , 2008, “ Wetting and Roughness,” Annu. Rev. Mater. Res., 38(1), pp. 71–99. [CrossRef]
Carey, V. P. , 2008, “ Wetting Phenomena and Contact Angles,” Liquid-Vapor Phase-Change Phenomena, 2nd ed., Taylor & Francis, New York, pp. 96–98.
Cassie, A. D. B. , and Baxter, S. , 1944, “ Wettabiity of Porous Surfaces,” Trans. Faraday Soc., 40, p. 546. [CrossRef]
Brinkman, H. C. , 1949, “ A Calculation of the Viscous Force Exerted by Flowing Fluid on a Dense Swarm of Particles,” Appl. Sci. Res., 1(1), pp. 27–34. [CrossRef]
Gebhart, B. , 1993, Heat Conduction and Mass Diffusion, McGraw-Hill, New York, Sec. 3.1.1.
Padilla, J. , 2014, “ Experimental Study of Water Droplet Vaporization on Nanostructured Surfaces,” Ph.D. dissertation, University of California at Berkeley, Berkeley, CA. https://escholarship.org/uc/item/5hb7v7m3
Kunkle, C. M. , and Carey, V. P. , 2016, “ Metrics for Quantifying Surface Wetting Effects on Vaporization Processes at Nanostructured Hydrophilic Surfaces,” ASME Paper No. HT2016-7203.


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Fig. 1

Droplet-spreading process

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Fig. 2

Synchronous spreading regions

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Fig. 3

Dimensionless mass flux variation at the droplet/layer boundary

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Fig. 4

Droplet feeding hemi-spreading

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Fig. 5

Tightly packed pillar structure on copper surface enhanced with ZnO nanostructures (6 nm seeding particles, grown in solution for 8 h) imaged with a scanning electron microscope

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Fig. 6

Comparison of droplet spread data with the model predicted variation of R̂ = R/Rs with t̂ = t/ts for surface prep 1: (a) linearplot and (b) log–log plot

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Fig. 7

Comparison of droplet spread data with the model predicted variation of R̂ = R/Rs with t̂ = t/ts for surface prep 2 with 2 μl droplet and surface prep 2 with 3 μl droplet

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Fig. 8

High-speed video frames for a 2 μl water droplet spreading on copper surface with a ZnO nanostructured layer

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Fig. 9

Spreading of a 2 μl water droplet on copper surface with a ZnO nanostructured layer: (a) initial spreading at t = 0.014 s and (b) hemi-spreading at t = 4 s

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Fig. 10

Experimentally determined variation of liquid front radius with time as a 2 μl droplet spreads on a nanostructured ZnO surface

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Fig. 11

Wicked flow from a capillary tube on a nanoporous layer



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