Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux

O’Hanley, Harrison F.; Coyle, Carolyn; Buongiorno, Jacopo; McKrell, Thomas; Hu, Lin‐Wen; Rubner, Michael F.; Cohen, Robert E.

doi:10.1063/1.4813450

Cited by 245 publications

(112 citation statements)

References 23 publications

(19 reference statements)

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“…Larger pores allow more efficient vapor escape at higher heat fluxes, thereby leading to higher CHF for coatings with higher porosities, consistent with findings from previous studies [11,37]. Between the two particle types, spherical particle coatings have slightly higher CHF at the same porosity compared to irregular particle coatings, which is consistent with the larger pore size observed in the images.…”

Section: Qualitative Image Analysis It Is Observed Fromsupporting

confidence: 82%

“…The dendritic porous structure was also said to increase agitation of the vapor bubbles inside the porous structure, thus enhancing single-phase convection heat transfer by up to six times. O'Hanley et al [11] performed experiments to study the effect of porosity on CHF during boiling of water from surfaces with different geometric properties (e.g., surface wettability and roughness). Silica nanoparticles were deposited on sapphire substrates to achieve the desired coating properties.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

Sarangi

Weibel

Garimella

2016

Journal of Heat Transfer

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Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux (CHF). However, there is no unified understanding of the role of coating characteristics on pool boiling heat transfer enhancement. The morphology and size of the particles affect the pore geometry, permeability, thermal conductivity, and other characteristics of the sintered coating. In turn, these characteristics impact the heat transfer coefficient and CHF during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular and spherical morphologies for a range of porosities (∼40–80%). Particles of the same effective diameter (90–106 μm) are sintered to yield identical coating thicknesses (∼4 particle diameters). The porous structure formed by sintering is characterized using microcomputed tomography (μ-CT) scanning to study the geometric and effective thermophysical properties of the coatings. The boiling performance of the porous coatings is analyzed. Coating characteristics that influence the boiling heat transfer coefficient and CHF are identified and their relative strength of dependence analyzed using regression analysis. Irregular particles yield higher heat transfer coefficients compared to spherical particles at similar porosity. The coating porosity, pore diameter, unit necking area, unit interfacial area, effective thermal conductivity, and effective permeability are observed to be the most critical coating properties affecting the boiling heat transfer coefficient and CHF.

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Section: Qualitative Image Analysis It Is Observed Fromsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

Sarangi

Weibel

Garimella

2016

Journal of Heat Transfer

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“…Note that the maximum enhancement was obtained in the steady-state tests, which would suggest a dependence of the CHF enhancement on the coating thickness. As found in a recent study of separate surface effects on CHF [40], CHF enhancement can be achieved if a network of interconnected hydrophilic pores exists on the surface. Then the differences seen among the tests with confirmed nanoparticle deposition (i.e.…”

Section: Discussionmentioning

confidence: 89%

“…The nanoparticle layer creates a network of interconnected porosity [40] on the heater surface and also imparts a higher hydrophilicity to the surface, as revealed by contact angle measurements for a drop of DI water on post-test heater surfaces. As shown in Figure 6, surface hydrophilicty of the heater surface was increased significantly upon formation of the nanoparticle deposition layer.…”

Section: Resultsmentioning

confidence: 99%

Experimental investigation of transient critical heat flux of water-based zinc–oxide nanofluids

Sharma

Buongiorno

McKrell

et al. 2013

International Journal of Heat and Mass Transfer

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Pool boiling experiments were conducted for sandblasted stainless steel (grade 316) plate heaters submerged in deionized (DI) water and water-based zinc-oxide nanofluid, for transient heat flux conditions with power through the heaters increasing quadratically with time. Heat flux in the experiments was increased from zero to CHF in short time frames of 1, 10 and 100 s. Consistent with previous studies, transient CHF for DI water was higher than steady state CHF, and CHF increased with decreasing duration of the transient. Additionally, it was observed that for nanofluid tests, a porous and hydrophilic nanoparticle layer started to deposit on the heater surface in short time frames of 10 and 100 s, and this layer was responsible for the enhanced CHF compared to DI water. However, for the 1 s tests, nanoparticle deposition did not occur and consequently the CHF was not enhanced. Finally, experiments with heaters pre-coated with nanoparticles were performed and it was found that CHF was enhanced for all transient durations down to 1 s, establishing firmly that the CHF enhancement occurs due to surface modifications by the deposited nanoparticles, and not by nanoparticles suspended in solution. Keywords

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“…Phase change heat transfer systems, such as pool and flow boiling heat sinks, are used extensively in the fields of refrigeration, air conditioning, and electronic devices cooling [1][2][3]. During the boiling heat transfer, the working fluid can absorb a large amount of heat with a small wall superheat due to its large latent heat of vaporization [4,5].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Effect of Size and Pitch of Hydrophobic Square Patterns on the Pool Boiling Heat Transfer Performance of Cylindrical Copper Surface

et al. 2018

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Abstract:In this work, pool boiling heat transfer tests were conducted for investigating the effects of the size and pitch of the hydrophobic square patterns on a copper test piece with the following dimensions: 40 mm long, 25 mm outer diameter, and 18 mm inner diameter. The size of the square patterns and the pitch were varied with an increment of 0.5 mm from 1 mm to 3 mm and from 4.5 to 5.5 mm, respectively. Among the various square patterns of different size and pitch, the 2 mm size square pattern with 5 mm pitch (inter-distance 3 mm) was found to be the best because it gives the advantage of bubble coalescence behavior and also the rewetting phenomenon. The observed bubble departure diameter was 2.35 mm, and using this diameter, we predicted the maximum inter-distance between the patterns for producing inter coalescence of bubbles in the axial direction was 3.12 mm. Therefore, a side-by-side distance of 3 mm, which was closed to the estimated inter-distance graphically, can avoid the earlier inter coalescence of the bubbles between patterns on the surface in the axial direction. This results in better pool boiling heat transfer performance. Highlights: (1) Heterogeneous wettable structures were obtained on the copper surface using screen printing techniques; (2) The effect of the size and pitch of the hydrophobic patterns on the bubble dynamics was determined; (3) The wall superheats of all the heterogeneous wettable surfaces were less than the plain copper surface; (4) The highest heat transfer coefficient was obtained from the hydrophobic pattern with 2 mm size and 5 mm pitch.

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Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux

Abstract: Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.

Cited by 245 publications

References 23 publications

Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

Experimental investigation of transient critical heat flux of water-based zinc–oxide nanofluids

Experimental Investigation on the Effect of Size and Pitch of Hydrophobic Square Patterns on the Pool Boiling Heat Transfer Performance of Cylindrical Copper Surface

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