Correlation of Surface and Interfacial Energies on Enhanced Pool Boiling Heat Transfer

Volume 3 ◽  
2004 ◽  
Author(s):  
Elva Mele´ndez ◽  
Rene´ Reyes
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Surface Energy ◽  
Interfacial Energy ◽  
Boiling Heat Transfer ◽  
Contact Angles ◽  
Lauryl Sulfate ◽  
Surface Energies ◽  
Interfacial Energies ◽  
Set Up

The surface energy of the material used in the construction of capillary covers is an important element to increase the boiling heat transfer on the coverings. There are a variety of methodologies for measuring the surface energy of solids, but few could be used with the construction materials tested. The sessile drop methodology allows the evaluation of either the surface energy of solids or the interfacial energy of liquids. The methodology uses an image digitalization system for measuring the contact angle of liquids on the solid’s surface. The contact angles thus measured are used to calculate the superficial and interfacial energies. This methodology was tested with an experimental set up built for this study. The accuracy of the set up was obtained with clean and greased surfaces of high heat conductivity metals. The surface energies calculated were in accordance with previous experimental results. The surface energies of metal foils used for construction of capillary coverings were similar to the values calculated for the parental solid metal. The surfaces with different grease thickness get values of surface energy close to the value for the adhered hydrocarbons. The same methodology is used for measuring interfacial energies of pure and mixtures of liquids. The liquids studied include those used for increasing boiling heat transfer. Ethanol-water mixtures were analyzed. The mixture with 16% ethanol by weight had the lowest contact angle (associated to the lowest interfacial energy) and produced the highest convective heat transfer coefficient, h. A minimum in the value of the contact angle around the 16% weight ethanol mixtures follows the maximum in the value of h around this composition, and a maximum in the wettability. Similarly, the surfactant sodium-lauryl-sulfate (SLS) produced an increment of the wettability of the mixture on the solid surface. The reduction of the contact angle is obtained with the addition of 100 ppm of SLS or less, depending on the base metal, but above this concentration, the surfactant does not modify the value of the contact angle. The h values increased with the addition of surfactant up to 100 ppm but do not change if the concentration of surfactant is higher than that value.

scholarly journals On the limitations of the applicability of Young’s equations temperature

2021 ◽  
Vol 23 (2) ◽  
pp. 218-222
Author(s):  
Magomed Pashevich Dokhov
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Interfacial Energy ◽  
Contact Angles ◽  
Surface Phenomena ◽  
Surface Energies ◽  
Three Phase ◽  
Production Techniques ◽  
The Difference ◽  
Solid Liquid

The article uses the thermodynamics of interfacial phenomena to justify the fact that Young’s equations can correctly describe the three-phase equilibrium with any type of interatomic bonds. Wetting, adhesion, dissolution, surface adsorption, and other surface phenomena are important characteristics, whichlargely determine the quality and durability of materials, and the development of a number of production techniques, including welding, soldering, baking of metallic and non-metallic powders, etc. Therefore, it is important to study them.Using experimental data regarding surface energies of liquids (melts) and contact angles available in the literature, we calculated the surface energies of many solid metals, oxides, carbides, and other inorganic and organic materials without taking into account the amount of the interfacial energy at the solid-liquid (melt) interface. Some researchers assumed that in case of an acute contact angle the interfacial energy is low. Therefore, they neglected it and assumed it to be zero.Others knew that this value could not be measured, that is why they measured and calculated the difference between the surface energy of a solid and the interfacial energy of a solid and a liquid (melt), which is equal to the product of the surface energy of this liquid by the cosine of the contact angle. It is obvious that these methods of determining the surface energy based on such oversimplified assumptions result in poor accuracy.Through the use of examples this paper shows how the surface energies of solids were previously calculated and how the shortcomings of previous calculations can be corrected

Experimental Verification of Analytical Prediction of Pool Boiling CHF Incorporating the Effects of EHD and Contact Angle

2015 ◽  
Author(s):  
Ichiro Kano ◽  
Takahiro Sato ◽  
Naoki Okamoto
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Electric Field ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Contact Angles ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Analytical Prediction ◽  
Compound Effect

Boiling heat transfer enhancement via compound effect of Electro-Hydro-Dynamic (EHD) and contact angle has been experimentally and analytically investigated. A fluorinated dielectric liquid (Asahi Glass Co. Ltd, AE-3000) was selected as the working fluid. Pool boiling heat transfer in the saturated liquid was measured at atmospheric pressure. In order to change the contact angle between the boiling surface and the dielectric liquid, the different materials Cu, Cr, NiB, Sn, and mixture of 5 and 1.5 micro meter diamond particles were electrically deposited on a boiling surface. The critical heat flux (CHF) for different contact angles showed 20.5 ∼ 26.9 W/cm2 which was −7 ∼ 25 % of that for a non-coated Cu surface (21.5 W/cm2). Upon application of a −5 kV/mm electric field to the micro structured surface (the mixture of 5 and 1.5 micro meter particles), a CHF of 99 W/cm2 at a superheat of 33.5 K was obtained. The previous theoretical equation of pool boiling predicted the CHF with the electric field and without the electrode.

The Measurement of Surface Energy by Video Analysis of Captive-Bubble Contact-Angles

1995 ◽  
Vol 75 (3) ◽  
pp. 763-766 ◽  
Author(s):  
Jeremy C. Thomas ◽  
John Davenport
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Video Analysis ◽  
Sea Water ◽  
Contact Angles ◽  
Marine Organisms ◽  
Surface Energies ◽  
Cyanea Capillata ◽  
Ptfe Sheet ◽  
Non Destructive

Surface energy has been demonstrated to have a significant effect upon the settlement and growth of many marine organisms. However, the measurement of surface energy has either been too expensive for most marine laboratories to consider its use, or the methods used have relied upon classical contact-angle theory. Modern contact-angle theory and a video-based technique using captive bubbles are described. The technique is non-destructive, inexpensive, rapid and accurate enough to compare living and man-made surfaces. A precision of ~5° has been achieved and rapidly-changing angles can be quantified. Data for PTFE sheet, Parafilm, acetate sheet, Geltek gel, sea-water-conditioned slate, Porphyra umbilicalis (L.) Agardh, Ciona intestinalis (L.), and Cyanea capillata (L.) are presented. The contact angles for the living surfaces are smaller (31–44°) than for all the non-living surfaces (73–112°), suggesting overall higher surface energies for the biological materials studied.

Synergism of Binary Mixtures Wettability and Cover Porosity on Enhanced Pool Boiling Heat Transfer

2004 ◽  
Author(s):  
Elva Mele´ndez ◽  
Rene´ Reyes
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Interfacial Energy ◽  
Boiling Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Water Mixture ◽  
Lauryl Sulfate ◽  
Maximum Heat ◽  
Maximum Heat Transfer

The wettability of the system in capillary covers is an important element to increase the boiling heat transfer on the coverings. The sessile drop methodology allows the evaluation of either the surface energy of solids or the interfacial energy of liquids, and from both the system’s wettability. This methodology was tested with an experimental set up built for this study. The surface energies calculated for solids and metal foils used for construction of capillary coverings were in accordance with previous experimental results. The same methodology is used for measuring interfacial energies of the liquids used for increasing boiling heat transfer like ethanol-water mixtures. The mixture with 16% ethanol by weight had the lowest contact angle (associated to the lowest interfacial energy) and produced the highest convective heat transfer coefficient, h. Thus, the maximum for h correlates with an increase in the wettability of this system. This behavior is related to that observed as the critical micelial concentration (cmc) for surfactants, that produce the lowest interfacial energy of the liquid. Thus a set of experiments was developed to correlate the binary mixture behavior around the concentration with maximum heat transfer coefficient with the cmc boiling behavior. The surfactant sodium lauryl sulfate (SLS) produced an increase of the wettability of the solid surface with the addition of 100 ppm (or less) that is its cmc. The h values increase with the addition of SLS up to 100 ppm but do not change if the concentration of surfactant is higher than that value. The maximum heat transfer coefficient is obtained with the cmc of SLS in water, and with the 16% by weight ethanol-water mixture, both having the highest wettability. Porous coverings were tested with two covering’s thickness. A synergistic effect is found for the appropriate cover thickness combined with either a 16% by weight ethanol-water mixture or water with the cmc of SLS.

scholarly journals Free Energy Balance of Polyamide, Polyester and Polypropylene Surfaces

2012 ◽  
Vol 7 (4) ◽  
pp. 155892501200700 ◽  
Author(s):  
Marcela Bachurová ◽  
Jakub Wiener
Keyword(s):  
Contact Angle ◽  
Free Energy ◽  
Energy Balance ◽  
Surface Energy ◽  
Solid Surface ◽  
Contact Angles ◽  
Surface Energies ◽  
Receding Contact ◽  
Smooth Plate

The wettability of a solid surface is often characterized by the contact angle of liquid on the solid surface. The wettability is pertinent to surface energy, which is an important parameter. The wettability can be affected, for example, by the roughness of the solid surface. In our work textiles are used as macroscopic roughness surfaces, and smooth plate surfaces are used as well to determine surface energies. For the calculation of surface energies it is fundamental to know the contact angle. The advancing and receding contact angles are measured, and the relation between the hysteresis and surface energy is monitored.

scholarly journals Surface energies emerging in a microscopic, two-dimensional two-well problem

2017 ◽  
Vol 147 (5) ◽  
pp. 1041-1089 ◽  
Author(s):  
Georgy Kitavtsev ◽  
Stephan Luckhaus ◽  
Angkana Rüland
Keyword(s):  
Surface Energy ◽  
Two Dimensional ◽  
Direct Control ◽  
First Order ◽  
Surface Energies ◽  
Energy Scaling ◽  
Continuous Analogue ◽  
Dimensional Shape ◽  
Set Up ◽  
Microscopic Modelling

In this paper we are interested in the microscopic modelling of a two-dimensional two-well problem that arises from the square-to-rectangular transformation in (two-dimensional) shape-memory materials. In this discrete set-up, we focus on the surface energy scaling regime and further analyse the Hamiltonian that was introduced by Kitavtsev et al. in 2015. It turns out that this class of Hamiltonians allows for a direct control of the discrete second-order gradients and for a one-sided comparison with a two-dimensional spin system. Using this and relying on the ideas of Conti and Schweizer, which were developed for a continuous analogue of the model under consideration, we derive a (first-order) continuum limit. This shows the emergence of surface energy in the form of a sharp-interface limiting model as well the explicit structure of the minimizers to the latter.

Surface energy effect on boiling heat transfer

2005 ◽  
Vol 41 (12) ◽  
pp. 1043-1047 ◽  
Author(s):  
Atul P. Patil ◽  
Vijaya C. B. Vittala
Keyword(s):  
Heat Transfer ◽  
Surface Energy ◽  
Boiling Heat Transfer ◽  
Energy Effect ◽  
Surface Energy Effect

Comparative Study of Surface Energies of Native Oxides of Si(100) and Si(111) via Three Liquid Contact Angle Analysis

MRS Advances ◽  
2018 ◽  
Vol 3 (57-58) ◽  
pp. 3379-3390 ◽  
Author(s):  
Saaketh R. Narayan ◽  
Jack M. Day ◽  
Harshini L. Thinakaran ◽  
Nicole Herbots ◽  
Michelle E. Bertram ◽  
...  
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Sessile Drop ◽  
Surface Composition ◽  
Ion Beam ◽  
Contact Angles ◽  
Van Der Waals Interactions ◽  
Native Oxides ◽  
Relative Errors ◽  
Contact Angle Analysis

ABSTRACTThe effects of crystal orientation and doping on the surface energy, γT, of native oxides of Si(100) and Si(111) are measured via Three Liquid Contact Angle Analysis (3LCAA) to extract γT, while Ion Beam Analysis (IBA) is used to detect Oxygen. During 3LCAA, contact angles for three liquids are measured with photographs via the “Drop and Reflection Operative Program (DROP™). DROP™ removes subjectivity in image analysis, and yields reproducible contact angles within < ±1°. Unlike to the Sessile Drop Method, DROP can yield relative errors < 3% on sets of 20-30 drops. Native oxides on 5 x 1013 B/cm3 p- doped Si(100) wafers, as received in sealed, 25 wafer teflon boats continuously stored in Class 100/ISO 5 conditions at 24.5°C in 25% controlled humidity, are found to be hydrophilic. Their γT, 52.5 ± 1.5 mJ/m2, is reproducible between four boats from three sources, and 9% greater than γT of native oxides on n- doped Si(111), which averages 48.1 ± 1.6 mJ/m2 on four 4” Si(111) wafers. IBA combining 16O nuclear resonance with channeling detects 30% more oxygen on native oxides of Si(111) than Si(100). While γT should increase on thinner, more defective oxides, Lifshitz-Van der Waals interactions γLW on native oxides of Si(100) remain at 36 ± 0.4 mJ/m2, equal to γLW on Si(111), 36 ± 0.6 mJ/m2, since γLW arises from the same SiO2 molecules. Native oxides on 4.5 x 1018 B/cm3 p+ doped Si(100) yield a γT of 39 ± 1 mJ/m2, as they are thicker per IBA. In summary, 3LCAA and IBA can detect reproducibly and accurately, within a few %, changes in the surface energy of native oxides due to thickness and surface composition arising from doping or crystal structure, if conducted in well controlled clean room conditions for measurements and storage.

Pool Boiling Heat Transfer of Water on Hydrophilic Surfaces With Different Wettability

2016 ◽  
Author(s):  
Adam R. Girard ◽  
Jinsub Kim ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Copper Surface ◽  
Contact Angles ◽  
Copper Surfaces ◽  
Nanoscale Structures ◽  
Flat Surfaces ◽  
Hydrophilic Surfaces ◽  
Alkali Solutions

The effect of wettability on boiling heat transfer (BHT) coefficient and critical heat flux (CHF) in pool boiling of water on hydrophilic surfaces having different contact angles was investigated. Hot alkali solutions were utilized to promote cupric and cuprous oxide growth which exhibited micro and nanoscale structures on copper surfaces, with thicknesses on the order of a couple of micrometers. These structure and surface energy variations result in different levels of wettability and roughness while maintaining the effusivity of the bare copper surface. The study showed that the BHT coefficient has an inverse relationship to wettability; the BHT coefficient decreases as wettability increases. Furthermore, it was shown that this dependency between BHT coefficient and wettability is more significant than the relationship between BHT coefficient and surface roughness. The CHF was also found to increase with increases in wettability and roughness. For the most hydrophilic surface tested in this study, CHF values were recorded near the 2,000 kW/m2 mark. This value is compared with maximum values reported in literature for water on non-structured flat surfaces without area enhancements. Based on these results it is postulated that there exists a true hydrodynamic CHF limit for pool boiling with water on flat surfaces, very near 2,000 kW/m2, independent of heater material, representing an 80% increase in the limit suggested by Zuber [1].

Study of the Combined Contributions of Porous Coverings and Mixture Surface Energies in Enhancing Pool Boiling

2006 ◽  
Author(s):  
Eric Siqueiros ◽  
Rene Reyes
Keyword(s):  
Heat Transfer ◽  
Binary Mixture ◽  
Convective Heat Transfer Coefficient ◽  
Boiling Water ◽  
Lauryl Sulfate ◽  
Surface Energies ◽  
Enhancing Heat Transfer ◽  
Aqueous Mixture ◽  
Covering Design ◽  
Comparison Of The Results

Factors as the boiling fluid surface tension and the characteristics of the solid surface where the heat transfer takes place could be modulated for increasing the boiling heat flux. In this work was observed the increase in the boiling convective heat-transfer coefficient (h) from the participation of: (a) the use of a binary mixture at its critical micelle concentration (16% w/w ethanol-water); (b) the addition of the surfactant sodium-lauryl-sulfate (SLS) to this aqueous mixture; and (c) the use of a porous covering fabricated from stainless steel bands with void volume 0.25, pore diameter 0.8 mm and covering thickness 8 mm. The sequence of results allowed the calculation of the relative participation of these factors in h (and the related values of excess temperature), for power supply from 100 to 1000 W on the same heater cartridge for all the experiments. For boiling water on the bare heater, hmax bare heater = 8.27 W/cm2 K; for boiling water on the porous covering, hmax covering = 19.36 W/cm2 K; the boiling of the water-ethanol (16%) mixture on the porous covering produced hmax covering+cmc = 31.72 W/cm2 K; and the binary mixture with 100 ppm of SLS, hmax covering+cmc+surfactant = 38.07 W/cm2 K. Considering this value of hmax covering+cmc+surfactant as the sum of the contributions, the relative participation of the mechanical forces breaking the escaping bubbles through the covering is 29.13%; the surface energies associated to the formation of micelle structures 32.47%; and the surface energies from the surfactant 16.67%. Thus, the search of enhancing heat transfer should consider the boiling mixture composition as well as the porous covering design. A comparison of the results obtained with the covering developed in this work with some coverings developed in a previous work reveals that the geometry of the covering material could be the base for heat transfer enhancement.

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