Optimum ratio of hydrophobic to hydrophilic areas of biphilic surfaces in thermal fluid systems involving boiling

Motezakker, Ahmad Reza; Sadaghiani, Abdolali Khalili; Çelik, Süleyman Utku; Larsen, Tom; Villanueva, Luis Guillermo; Koşar, Ali

doi:10.1016/j.ijheatmasstransfer.2019.01.139

Cited by 110 publications

(37 citation statements)

References 33 publications

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“…As a result, the authors reported that the three-phase contact line was more likely to be dislodged from the edge of the hydrophobic spot under sufficiently low-pressure conditions, where particularly quick bubble growth tended to prevail. An investigation to find a novel and facile process flow for the fabrication of biphilic surfaces was proposed and tested by Reference [ 31 ]. The researchers studied ten biphilic surfaces with hydrophilic/total areas ranging from 0.19% to 95% and they tested them, to analyze the effect of heterogeneous wettability.…”

Section: Introductionmentioning

confidence: 99%

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

et al. 2021

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This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.

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Section: Introductionmentioning

confidence: 99%

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

et al. 2021

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“…For instance, (Sadaghiani et al, 2020a;Sadaghiani et al, 2020b) studied the effect of artificial cavities on three phase contact line and reported an optimum ratio of diameter to pitch distance, which maximized the heat transfer coefficient in pool boiling. Similarly, it was reported that biphilic surfaces resulted in enhancements of pool boiling heat transfer (Motezakker et al, 2019) and flow boiling heat transfer . According to Honda and Wei (Honda et al, 2002), micro structures such as micro-roughness and micro-porous coatings significantly facilitated the incipience of boiling, while delaying the CHF (critical heat flux).…”

Section: Introductionmentioning

confidence: 74%

“…Experimental studies proved that hydrophobic substrates provide higher heat transfer coefficients in flow boiling in micro- (Choi et al, 2011;Kim and Lee, 2019) and minichannels (Phan et al, 2011;Zhao et al, 2021) in comparison with hydrophilic ones. Generally, low energy surfaces (hydrophobic) remarkably augment the onset of nucleate boiling and bubble departure, while high energy surfaces (hydrophilic) enhance liquid replenishment and raises the critical heat flux (Motezakker et al, 2019;Sadaghiani et al, 2020a;Tan et al, 2021). Therefore, recent studies suggest that surface modification is an effective method to improve heat transfer via phase-change heat transfer including droplet evaporation (Dai et al, 2014;Aboubakri et al, 2020), flow condensation (Chehrghani et al, 2021), flow and pool boiling (Shojaeian and Koşar, 2015).…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Biphilicity on FC-72 Flow Boiling in a Rectangular Minichannel

et al. 2021

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Flow boiling is one of the most effective mechanisms in heat transfer thanks to the latent heat of vaporization. Surface modifications such as mixed-wettability have a considerable effect on the boiling heat transfer performance in terms of enhancement in boiling heat transfer as well as critical heat flux. This study introduces a new method of fabrication of biphilic surfaces, where C4F8 (Octafluorocyclobutane) islands are surrounded by silicon. Two different biphilic surfaces were fabricated and compared with the entirely uniform hydrophobic surface taken as a reference,. Each of the biphilic surfaces has three different sections, namely inlet, middle and outlet regions. The first region is mainly hydrophobic (inlet), while the third region is mainly hydrophilic (outlet). The heat transfer coefficients were obtained at different heat fluxes. Compared to the entirely uniform hydrophobic surface, the results show that biphilic surfaces enhance the boiling heat transfer performance by up to 50%. The visualization results revealed that the biphilic surfaces lead to more nucleation sites in the bubbly flow regime and break up the elongated bubbles in the slug flow regime.

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“…Many surface modification techniques [5], [6] have been proposed and investigated to achieve these goals. These techniques include implementation of nanowire arrays [7], nanorods [8], graphene coating [9], polymer coating [10], [11], virus coating [12], biphilic surfaces [13], porous surfaces [14], laser-engineered surfaces [15], and plasma spray coating [16]. Based on the application and the range of the applied heat fluxes, these three aspects should be considered in the design of thermal-fluids systems to maximize the heat removal from the surface in nucleate boiling and film boiling regimes.…”

Section: Introductionmentioning

confidence: 99%

Bio-coated surfaces with micro-roughness and micro-porosity: Next generation coatings for enhanced energy efficiency

Niazi

Sadaghiani

Gharıb

et al. 2021

Energy

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Due to growing cooling demands as well as emerging global warming and climate change issues, cooling systems should be more efficiently utilized. Boiling is an effective heat transfer mechanism, which has a critical role in many cooling systems. Surface modification is considered as the major approach for boiling heat transfer enhancement. In this study, we developed a microbial bio-coating surface modification technique for phase change cooling applications.Thermoacidophilic Sulfolobus solfataricus coating was implemented using a facile dip coating method on different metallic and non-metallic surfaces. Controlled by drying conditions, the coating exhibited rough and porous morphologies. When tested in a boiling heat transfer setup, bio-coated surfaces offered enhancements up to 76.3% in Critical Heat Flux (CHF). Next, a miniature evaporator was coated and tested for real-world air-conditioning applications, and coefficient of performance (COP) enhancements up to 11% clearly revealed the potential of biocoated surfaces for energy saving purpose and reduction in greenhouse gasses. Furthermore, coated evaporators reduced the exergy destruction rate up to 8%. This study not only offers a new type of coating morphology, but the applicability of the proposed bio-coating is also proven in a miniature air conditioning system.

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Optimum ratio of hydrophobic to hydrophilic areas of biphilic surfaces in thermal fluid systems involving boiling

Cited by 110 publications

References 33 publications

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Pool Boiling of Nanofluids on Biphilic Surfaces: An Experimental and Numerical Study

Effect of Surface Biphilicity on FC-72 Flow Boiling in a Rectangular Minichannel

Bio-coated surfaces with micro-roughness and micro-porosity: Next generation coatings for enhanced energy efficiency

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