In this paper, pool boiling heat transfer from smooth surfaces with mixed wettability is investigated based on a recently developed phase-change lattice Boltzmann method, which is capable of ...simulating the entire ebullition cycle beginning from the bubble nucleation process. It is demonstrated that addition of hydrophobic spots on smooth hydrophilic surfaces promotes bubble nucleation, enhancing boiling heat transfer and reducing nucleation time drastically. The mixed wettability surface is also expected to enhance critical heat flux (CHF) by regulating vapor spreading behaviors over the heater surface. Temperature variations beneath the growing vapor bubble and total boiling heat flux variations during bubble growth process are also investigated. The ebullition cycle is found to have a dominant effect on temporal variations of temperature and total boiling heat flux. Local heat flux distributions on the hydrophobic and the hydrophilic regions are analyzed, and the three-phase contact line (TCL) region is found to have the highest local heat flux. Effects of the size of the hydrophobic spots and pitch distance between these hydrophobic spots on boiling heat transfer are illustrated.
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Thermo gravimetric analysis for pure dolomite and treated surfaces with different surfactant solutions at 0.3wt.%. Display omitted
► A mechanistic study on wettability alteration during surfactant ...flooding was presented. ► This study was implemented on carbonate rocks with different analytical instruments. ► The role of surfactants’ structure in wetting change process was reported. ► Cationic surfactant is more effective in changing the wettability of dolomite rock. ► C12TAB irreversibly desorbs stearic acid from dolomite surface via ionic interaction.
A considerable quantity of the world's oil reserve is located in naturally fractured carbonate reservoirs, with very low oil recovery efficiency, due to their wettability and tightness of matrixes. Recovery efficiency can be improved considerably, if the reservoir rock wettability is changed from mostly oil-wet to water-wet, thus enhancing water imbibition into the oil saturated rock. In this experimental work, an extensive mechanistic study is performed utilizing different analytical tools to study the effects of surfactants on the sample rock's wettability. The results indicate that the surfactants act in different manners according to their structure. Cationic surfactant C12TAB, tends to irreversibly desorb stearic acid from the dolomite surface via ionic interaction. Nonionic surfactant TritonX-100 is adsorbed on the surface by the polarization of π electrons and ion exchange, releasing more stearic acid from the solid surface. The released stearic acid is then adsorbed as a new layer on the surface, through hydrophobic interaction between the tail of adsorbed surfactants and the non-polar part of the stearic acid. Anionic surfactants, such as SDS, are adsorbed on the surface via hydrophobic interaction between the tail of surfactant and the adsorbed acid, thus changing the wettability of the surface to a neutral wet condition.
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Large-scale underground hydrogen storage (UHS) appears to play an important role in the hydrogen economy supply chain, hereby supporting the energy transition to net-zero carbon emission. To ...understand the movement of hydrogen plume at subsurface, hydrogen wettability of storage rocks has been recently investigated from the contact angles rock-H2-brine systems. However, hydrogen wettability of shale formations, which determines the sealing capacity of the caprock, has not been examined in detail. In this study, semi-empirical correlations were used to compute the equilibrium contact angles of H2/brine on five shale samples with various total organic content (TOC) at various pressures (5–20 MPa) and at 343 K. The H2 column height that can be securely trapped by the shale and capillary pressures were calculated. The shale's H2 sealing capacity decreased with increasing pressure, increasing depth and TOC values. The CO2/brine equilibrium contact angles were generally higher than H2/brine equilibrium, suggesting that CO2 could be used as favorable cushion gas to maintain formation pressure during UHS. The utmost height of H2 that can be safely trapped by shale 3 (with TOC of 23.4 wt%) reduced from 8950 to 8750 M while that of shale 5 (with TOC of 0.081 wt%) reduced slightly from 9100 M to 9050 M as the pressure was increased from 5 to 20 MPa. The capillary entry pressure decreased with increasing depth and shale TOC, implying that the capillary trapping effect, as well as the over-pressure required to move brines from the pores by hydrogen displacement, reduces with increasing depth, and shale TOC. However, the shales remained at strongly water-wet conditions, having an equilibrium contact angles of not more than 17° at highest pressure and TOC. The study suggests that the increasing contact angles with increasing pressure and shale TOC, as well as decreasing column height and capillary pressure with increasing depth for H2-brine-shale systems might not be sufficient to exert significant influence on structural trapping capacities of shale caprocks due to low densities of hydrogen.
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•Hydrogen wettability of cap-rock (shale) was studied.•H2 column height that can be securely trapped by the shale was calculated.•Sealing capacity decreased with increasing pressure and TOC values.•The shales remained at strongly water-wet conditions, with contact angle < 17°.•Hydrogen wettability of shale is lower than CO2 wettability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The practical applications of skin‐interfaced sensors and devices in daily life hinge on the rational design of surface wettability to maintain device integrity and achieve improved sensing ...performance under complex hydrated conditions. Various bioinspired strategies have been implemented to engineer desired surface wettability for varying hydrated conditions. Although the bodily fluids can negatively affect the device performance, they also provide a rich reservoir of health‐relevant information and sustained energy for next‐generation stretchable self‐powered devices. As a result, the design and manipulation of the surface wettability are critical to effectively control the liquid behavior on the device surface for enhanced performance. The sensors and devices with engineered surface wettability can collect and analyze health biomarkers while being minimally affected by bodily fluids or ambient humid environments. The energy harvesters also benefit from surface wettability design to achieve enhanced performance for powering on‐body electronics. This review first summarizes the commonly used approaches to tune the surface wettability for target applications toward skin‐interfaced sensors and devices. By considering the existing challenges, one also discusses the opportunities as a small fraction of potential future developments, which can lead to a new class of skin‐interfaced devices for use in digital health and personalized medicine.
The surface wettability design can provide skin‐interfaced sensors and devices with unique functions to collect and analyze health biomarkers while being minimally affected by bodily fluids or ambient aqueous environments. This review summarizes commonly used approaches to prepare varying surface wettability and resulting skin‐interfaced devices for target applications. The prospects for future developments toward stretchable self‐powered devices are also discussed.
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Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation and efficient ...droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, these properties have conflicting requirements on the structural roughness and surface chemistry of the condensing surface or condensation modes (e.g., filmwise vs dropwise). Despite intensive efforts over the past few decades, almost all studies have focused on the dropwise condensation enabled by superhydrophobic surfaces. In this work, we report the development of a bioinspired hybrid surface with high wetting contrast that allows for seamless integration of filmwise and dropwise condensation modes. We show that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient. Moreover, we propose an analytical model to optimize the surface morphological features for dramatic heat transfer enhancement.
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•For the first time, we experimentally quantify the intrinsic contact angle of H2/Brine/Sandstone Rock.•The studies are done by developing a Captive-Bubble setup at high-pressure and elevated ...temperatures.•The measurements are done for different T, P, salinity, and rock type representing in-situ conditions.•With the results presented in this paper one can quantify relative permeability (Kr) and capillary pressure (Pc) curves for accurate reservoir-scale modeling and simulation.
Subsurface porous formations provide large capacities for underground hydrogen storage (UHS). Successful utilization of these porous reservoirs for UHS depends on accurate quantification of the hydrogen transport characteristics at continuum (macro) scale, specially in contact with other reservoir fluids. Relative-permeability and capillary-pressure curves are among the macro-scale transport characteristics which play crucial roles in quantification of the storage capacity and efficiency. For a given rock sample, these functions can be determined if pore-scale (micro-scale) surface properties, specially contact angles, are known. For hydrogen/brine/rock system, these properties are yet to a large extent unknown. In this study, we characterize the contact angles of hydrogen in contact with brine and Bentheimer and Berea sandstones at various pressure, temperature, and brine salinity using captive-bubble method. The experiments are conducted close to the in-situ conditions, which resulted in water-wet intrinsic contact angles, about 25 to 45 degrees. Moreover, no meaningful correlation was found with changing tested parameters. We monitor the bubbles over time and report the average contact angles with their minimum and maximum variations. Given rock pore structures, using the contact angles reported in this study, one can define relative-permeability and capillary-pressure functions for reservoir-scale simulations and storage optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A novel silver nanoparticles (AgNPs)/chitosan composite dressing with asymmetric wettability surfaces was successfully prepared via a simple two-step method for biomedical applications as wound ...healing materials. First, AgNPs were assembled into the chitosan sponge which was prepared by lyophilization process. Then one side of the sponge was modified by a thin layer of stearic acid. The incorporation of AgNPs into chitosan dressing could enhance the antibacterial activity against drug-sensitive and drug-resistant pathogenic bacteria. The asymmetric surface modification endows the dressing with both highly hydrophobic property and inherent hydrophilic nature of chitosan. The hydrophobic surface of the dressing shows waterproof and antiadhesion for contaminant properties, whereas the hydrophilic surface preserves its water-absorbing capability and efficiently inhibits the growth of bacteria. Furthermore, the AgNPs/chitosan composite dressing displays improved moisture retention and blood clotting ability compared to the unmodified dressings. Cytocompatibility test evaluated in vitro and in a wound infection model illustrates the nontoxic nature of the composite dressing. More importantly, the in vivo wound healing model evaluation in mice reveals that the asymmetric AgNPs/chitosan dressing promotes the wound healing and accelerates the reepithelialization and collagen deposition. The silver accumulation in mice body treated by the composite dressing is far lower than that of the clinically used Acasin nanosilver dressing treated mice. This work indicates the huge potential of the novel AgNPs/chitosan wound dressing with asymmetrical wettability for clinical use.
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Actualization of the hydrogen (H
) economy and decarbonization goals can be achieved with feasible large-scale H
geo-storage. Geological formations are heterogeneous, and their wetting ...characteristics play a crucial role in the presence of H
, which controls the pore-scale distribution of the fluids and sealing capacities of caprocks. Organic acids are readily available in geo-storage formations in minute quantities, but they highly tend to increase the hydrophobicity of storage formations. However, there is a paucity of data on the effects of organic acid concentrations and types on the H
-wettability of caprock-representative minerals and their attendant structural trapping capacities.
Geological formations contain organic acids in minute concentrations, with the alkyl chain length ranging from C
to C
. To fully understand the wetting characteristics of H
in a natural geological picture, we aged mica mineral surfaces as a representative of the caprock in varying concentrations of organic molecules (with varying numbers of carbon atoms, lignoceric acid C
, lauric acid C
, and hexanoic acid C
) for 7 days. To comprehend the wettability of the mica/H
/brine system, we employed a contact-angle procedure similar to that in natural geo-storage environments (25, 15, and 0.1 MPa and 323 K).
At the highest investigated pressure (25 MPa) and the highest concentration of lignoceric acid (10
mol/L), the mica surface became completely H
wet with advancing (θ
= 106.2°) and receding (θ
=97.3°) contact angles. The order of increasing θ
and θ
with increasing organic acid contaminations is as follows: lignoceric acid > lauric acid > hexanoic acid. The results suggest that H
gas leakage through the caprock is possible in the presence of organic acids at higher physio-thermal conditions. The influence of organic contamination inherent at realistic geo-storage conditions should be considered to avoid the overprediction of structural trapping capacities and H
containment security.
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•Anionic and natural surfactants used to investigate reservoir rocks mineralogy.•SDBS provided the maximum wettability changes for quartz surface.•Zizyphus Spina Christi decreases the wettability in ...dolomite core and quartz core.•SDBS decreases the wettability in quartz core.
Minerals surface properties have played a substantial to predict the rock mineralogy and chemical materials interactions, especially in chemical flooding (e.g., polymers, surfactant). In this paper, two different surfactants; nonionic surfactant (Zizyphus Spina Christi) and anionic surfactant (henceforth; SDBS) were used to experimentally investigate the minerals of reservoir rocks especially carbonate reservoirs and measure wettability changes accordingly. The contact angle evaluations have depicted that utilized surfactants change the wettability of pellet surfaces of calcite, dolomite, quartz, and anhydrite to neutral-wet or slightly water-wet. As it was observed, SDBS provided the maximum wettability changes for quartz surface. Moreover, the Zizyphus Spina Christi and SDBS have provided efficient performances on the decrease of wettability changes and residual oil saturation in dolomite core and quartz core, respectively. According to the results of this study, the oil recovery factor with anionic SDBS surfactant for calcite, dolomite, and quartz plugs are 66%, 41%, and 93%, respectively. This increase is more visualized for quartz cores that indicated the compatibility of this surfactant with quartz core samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study explored the feasibility of biosurfactant amendment in modifying the interfacial characteristics of carbon dioxide (CO
) with rock minerals under high-pressure conditions for GCS. In ...particular, while varying the CO
phase and the rock mineral, we quantitatively examined the production of biosurfactants by
and their effects on interfacial tension (IFT) and wettability in CO
-brine-mineral systems. The results demonstrated that surfactin produced by
caused the reduction of CO
-brine IFT and modified the wettability of both quartz and calcite minerals to be more CO
-wet. The production yield of surfactin was substantially greater with the calcite mineral than with the quartz mineral. The calcite played the role of a pH buffer, consistently maintaining the brine pH above 6. By contrast, an acidic condition in CO
-brine-quartz systems caused the precipitation of surfactin, and hence surfactin lost its ability as a surface-active agent. Meanwhile, the CO
-driven mineral dissolution and precipitation in CO
-brine-calcite systems under a non-equilibrium system altered the solid substrates, produced surface roughness, and caused contact angle variations. These results provide unique experimental data on biosurfactant-mediated interfacial properties and wettability in GCS-relevant conditions, which support the exploitation of
biosurfactant production for biosurfactant-aided CO
injection.
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