Modeling of Sessile Droplet Evaporation on Engineered Surfaces

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Jyoti Prakash ◽  
Basant Singh Sikarwar
Keyword(s):  
Experimental Study ◽  
Relative Humidity ◽  
Evaporation Rate ◽  
Sessile Drop ◽  
Droplet Evaporation ◽  
Contact Angles ◽  
Surface Wettability ◽  
Aluminum Surface ◽  
Complex Nature ◽  
Wide Range

The evaporation of sessile drop has a wide range of application that includes printing, washing, cooling, and coating. Due to the complex nature of drop evaporation process, this phenomenon is reliant on several parameters such as ambiance and physiochemical properties of liquid and surface. In the present study, a mathematical model of water droplet evaporation on an engineered aluminum surface is developed. Experimental study is carried out for the validation of code. The data obtained from the simulation is validated against the data obtained from an experimental study as well as the data available in the literature and good agreement was found among them. Post-validation, the effect of surface wettability and environment conditions on a droplet evaporation rate is estimated. It is inferred from the outcomes that the temperature at the apex of the drop varies linearly with the increasing relative humidity. Droplet volume has a significant impact on the evaporation rate and comparatively higher evaporative flux for a smaller volume of the drop with large contact angles. This unveils the possibility of achieving the required evaporation rate by controlling surface wettability and relative humidity conditions near the drop.

Air-Side Surface Wettability Effects on the Performance of Slit-Fin-and-Tube Heat Exchangers Operating Under Wet-Surface Conditions

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
L. Liu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Side Surface ◽  
Contact Angles ◽  
Surface Wettability ◽  
Retention Data ◽  
New Approach ◽  
Surface Conditions ◽  
Wide Range

A study of condensate retention and the attendant thermal-hydraulic effect associated with changes in air-side surface wettability is presented for a series of slit-fin-and-tube heat exchangers of identical geometry with controlled wettability covering a wide range of contact angles. An experiment in which the retained mass of air-side condensate was measured under dynamic conditions is described, and the results are analyzed using conventional thermal-hydraulic measurements of j and f. The data demonstrate that for the heat exchangers used in this study, the j factor is not strongly influenced by condensate retention, but the friction factor is significantly reduced for surfaces of increased wettability. Hydrophilic heat exchangers retain much less air-side condensate than do the hydrophobic heat exchangers, and the amount of retention is found to depend on the air-side Reynolds number (Redh) and the rate of latent heat transfer (Ql). Based on an assumption of filmwise condensation, a new model for predicting the mass of retained condensate is described and compared with the steady-sate retention data. The model is successful in predicting retained condensate over a wide range of tested conditions. The potential of this new approach and possible refinements that will add engineering value are discussed.

Experimental Study on Contact Angle of Water Droplet in High-Temperature Condition

2006 ◽  
Author(s):  
Yoshinori Hirose ◽  
Tsukasa Hayashi ◽  
Tatsuya Hazuku ◽  
Tomoji Takamasa
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Water Droplet ◽  
Contact Angles ◽  
Point Of View ◽  
Surface Wettability ◽  
Atmospheric Gases ◽  
Two Phase ◽  
Test Plate ◽  
High Temperature Condition

In recent decades, a number of reports have pointed out the importance of the influence of wall wettability on gas-liquid two-phase flow with a gas-liquid or liquid-gas phase change. However, very limited experimental data can be obtained about the wall surface wettability in BWRs high-temperature condition, or in the range from 250 to 300°C. From this point of view, we conducted an experimental study of surface wettability of droplet using a pressure vessel, we measured contact angles of water droplet under various ambient pressures (7.7, 14 and 15 MPa), atmospheric gases (nitrogen and argon), and test plate materials (aluminum, stainless 304, Zircaloy). In addition, experimental correlation was derived based on energy balance. The data obtained in this study will provide more accurate assessment of heat transfer in subchannels of BWRs.

scholarly journals The Effect of Exposed Glass Fibers and Particles of Bioactive Glass on the Surface Wettability of Composite Implants

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Aous A. Abdulmajeed ◽  
Lippo V. Lassila ◽  
Pekka K. Vallittu ◽  
Timo O. Närhi
Keyword(s):  
Bioactive Glass ◽  
Sessile Drop ◽  
Glass Fibers ◽  
Contact Angles ◽  
Surface Wettability ◽  
Reinforced Composites ◽  
Predictive Index ◽  
Plane Distribution ◽  
Composite Substrates ◽  
Hydrophilic Materials

Measurement of the wettability of a material is a predictive index of cytocompatibility. This study was designed to evaluate the effect of exposed E-glass fibers and bioactive glass (BAG) particles on the surface wettability behavior of composite implants. Two different groups were investigated: (a) fiber reinforced composites (FRCs) with different fiber orientations and (b) polymer composites with different wt. % of BAG particles. Photopolymerized and heat postpolymerized composite substrates were made for both groups. The surface wettability, topography, and roughness were analyzed. Equilibrium contact angles were measured using the sessile drop method. Three liquids were used as a probe for surface free energy (SFE) calculations. SFE values were calculated from contact angles obtained on smooth surfaces. The surface with transverse distribution of fibers showed higher () polar () and total SFE () components (16.9 and 51.04 mJ/m2, resp.) than the surface with in-plane distribution of fibers (13.77 and 48.27 mJ/m2, resp.). The increase in BAG particle wt. % increased the polar () value, while the dispersive () value decreased. Postpolymerization by heat treatment improved the SFE components on all the surfaces investigated (). Composites containing E-glass fibers and BAG particles are hydrophilic materials that show good wettability characteristics.

scholarly journals Thermodynamics of Oils of Nutritional/Cosmetic Use: Bertholletia excelsa, Cocos nucifera, and Pterodon emarginatus Vogel

2020 ◽  
Vol 3 (4) ◽  
pp. 347-353
Author(s):  
Marta A. Pires ◽  
Rebecca S. Andrade ◽  
Miguel Iglesias
Keyword(s):  
Fatty Acids ◽  
Experimental Study ◽  
Temperature Effect ◽  
Ultrasonic Velocity ◽  
Cocos Nucifera ◽  
Complex Nature ◽  
Brazil Nut ◽  
Bertholletia Excelsa ◽  
Molecular Group ◽  
Wide Range

This paper contains the results of a new experimental study about the temperature effect on density and ultrasonic velocity for Brazil nut (Bertholletia excelsa), coconut (Cocos nucifera), and sucupira (Pterodon emarginatus Vogel) oils. Isentropic compressibilities and isobaric expansibilities were computed from the experimental magnitudes as a function of temperature. Halvorsen’s model (HM), and Collision Factor Theory (CFT) were selected for the prediction of these properties due to their wide range of application and easy computation. An accurate response was observed, despite the use of several simplifications as molecular group contribution procedures for estimation of theoretic criticals points of the fatty acids and the complex nature of the studied fluids.  

Experimental Investigation on Silver-Graphene Hybrid Nanofluid Droplet Evaporation and Wetting Characteristics of its Nanostructured Droplet Residue

2019 ◽  
Author(s):  
Farooq R. Siddiqui ◽  
Edwin C. Y. Tso ◽  
Sau C. Fu ◽  
Christopher Y. H. Chao ◽  
Huihe Qiu
Keyword(s):  
Evaporation Rate ◽  
Volume Fraction ◽  
Spray Cooling ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Nanoporous Structure ◽  
Hybrid Nanofluid ◽  
Mixing Ratios ◽  
Static Contact ◽  
Wide Range

Abstract Droplet evaporation is a complex phase change process with a wide range of cooling applications, such as spray cooling and dropwise hotspot cooling in microelectronics, to name a few. The hybrid nanofluid droplet evaporation and its residue effects on evaporation of the subsequent hybrid nanofluid droplet is investigated in this research. Silver-graphene (Ag-GNP) hybrid nanofluid exhibiting synergistic thermal properties is investigated and prepared by dispersing silver nanoparticles along with graphene nanoplatelets in water at 0.1% volume fraction and with different mixing ratios, followed by ultrasonication. The evaporation rate and wetting characteristics of a 3 μl volume of Ag-GNP hybrid nanofluid droplet on a copper surface were studied using an optical tensiometer. Once dried, the nanoporous structure of the residue surface was examined using a scanning electron microscope, while the surface roughness was measured using an optical profiler. Experiments were continued to further investigate the evaporation rate and wetting effects of the subsequent Ag-GNP hybrid nanofluid droplet over the residue surface. The results showed improved wetting characteristics, with 88% reduction in initial static contact angle and 163–196% enhancement in evaporation rate of the subsequent Ag-GNP hybrid nanofluid droplets over the residue surfaces as compared to the copper surface.

Surface Wettability Effects in Heat and Fluid Flow

2006 ◽  
Author(s):  
Yasuyuki Takata
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Two Phase Flow ◽  
Contact Angles ◽  
Bubble Nucleation ◽  
Surface Wettability ◽  
Water Repellent ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range

Effects of surface wettability on liquid-vapor phase change phenomena and single- and two-phase flow in tube have been studied in wide range of contact angles using superhy drophilic (SH) and super-water-repellent (SWR) surfaces. Heat transfer in falling film evaporation on a TiO2-coated SH surface is tremendously enhanced due to very thin stable film. In pool bioling, critical heat flux (CHF) and minimum heat flux (MHF) increase with the decrease in contact angle. Wetting limit temperature of water drop on heated surface increases with the decrease in contact angle. In pool boiling on SWR surface, bubble nucleation and film boiling occur in extremely small superheating. Drag reduction was observed in water flow in tube with SWR coating in laminar flow region, and on the other hand, in two-phase flow pressure drop for the SH wall is smaller than that for the SWR wall.

Experimental Study of Brine Droplet Evaporation and Crystallization at Various Temperatures and Humidity Using EDB Method and Pendant Droplet Method

2019 ◽  
Author(s):  
Jie Qu ◽  
Luis Escobar ◽  
Zhonghao Rao ◽  
Ben Xu
Keyword(s):  
Relative Humidity ◽  
High Speed ◽  
Evaporation Rate ◽  
Crystallization Process ◽  
Dynamic Balance ◽  
Pure Water ◽  
Test Chamber ◽  
Droplet Evaporation ◽  
Water Molecules ◽  
Droplet Method

Abstract In this study, both electro-dynamic balance (EDB) method and pendant droplet method were employed to study the evaporation and crystallization process of brine droplet. The EDB setup was used to levitate the charged micrometer sized droplets to study the evaporation process. The pendant droplet method could hang millimeter sized droplet to study the crystallization process. The evaporation of brine droplets with different mass concentrations was visualized by a high speed camera under different temperatures and relative humidity in the test chamber. The results showed that EDB method could get the accurate droplet evaporation results which obeyed the classic D2-law. It was found that the evaporation was increased with the decrease of relative humidity. Due to the attractive force provided by sodium and chloride ion on water molecules, evaporation rate of brine droplet was smaller than pure water, therefore the evaporation rate decreased with the increase of mass concentration by showing a linear relationship. In addition, a salt shell could be formed at the outside of droplet which still contained some amount of salt solution inside. Consequently, the water molecules need to overcome the pressure difference inside and outside the salt shell, and diffuse through the shell for further evaporation. For a higher relative humidity, a more round shell would be formed during the evaporation, and the growth of crystallization along the filament is weaker than that of smaller relative humidity. We hope this study can provide a different perspective to the heat transfer community about the evaporation of brine droplet.

Temperature Dependence of the Contact Angle of Water on a Hydrophobic Surface at Pressurized Condition

2020 ◽  
Author(s):  
Jia-Wen Song ◽  
Meng-Chen Ma ◽  
Li-Wu Fan
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Temperature Dependence ◽  
Sessile Drop ◽  
Hydrophobic Surface ◽  
Contact Angles ◽  
Surface Wettability ◽  
Surface Thermodynamics ◽  
Temperature Spectrum ◽  
Phase Change Heat Transfer

Abstract It is of both practical and scientific significance to study the temperature dependence of contact angles, towards development of surface wettability manipulation techniques for enhanced phase change heat transfer as well as the theoretical estimation of solid interfacial energy. However, the variations of surface wettability of a hydrophobic solid with altering temperature remain unclear. In this work, in situ characterizations of the contact angle of water on Teflon (PTFE) surfaces as well as the surface tension of water over a temperature spectrum from ∼25 °C to 160 °C at pressurized condition (2 MPa) were conducted by employing the sessile drop and pendant drop methods, respectively. A nearly invariant trend of the contact angle of water was observed over the entire temperature range. Moreover, it was shown that the surface tension of water linearly declines with raising the temperature. Based on the theory of surface thermodynamics, the effects of temperature on the contact angles were analyzed with the variations of interfacial tensions.

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