Hydrophobic Conditions Research Articles

Modeling Water Clusters: Spectral Analyses, Gaussian Distribution, and Linear Function during Time

Our experimental and theoretical studies have consistently revealed the presence of water clusters in various environments, particularly under hydrophobic conditions, where slower hydrogen ion interactions prevail. Crucial methods like Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) method have played a pivotal role in our understanding of these clusters, unveiling their potential medical applications. The stability and behavior of these clusters can be influenced by factors such as metal ions’ presence, leading to stable clusters’ formation. This potential for medical applications should inspire hope and further research. Moreover, our research has revealed that water clusters exhibit characteristics of dissipative structures, demonstrating the self-organization under physical, chemical, or thermal changes akin to Rayleigh–Benard convection cells. This dynamic and significant behavior supports the notion that water’s role transcends simple chemistry, potentially influencing biological processes at a fundamental level. The interaction of water clusters with their environment and the ability to maintain non-equilibrium states through the energy exchanges further underscores their complexity and significance in both natural and technological contexts. Water filtration is a process for improving water quality. The effect is re-structuring hydrogen bonds and structuring water clusters, most of which are hexagonal. In our research, we applied filtered water using patented EVOdrop Swiss technology.

Multistability of a long droplet in a capillary tube under transverse body force

Bistable states for a sufficiently large amount of liquid can appear in an eccentric capillary due to the eccentricity effect under zero gravity (J. Fluid Mech, vol. 863, 2019, pp. 364–385). A transverse body force, which can lead to rich physical phenomena of a droplet, may lead to multistable states (bistability, tristability and the likes) of a sufficiently large amount of liquid in a capillary. We theoretically investigate this situation in a circular or annular capillary tube under a transverse body force. The results show that there can be tristable (bistable) states in an annular (circular) capillary tube: an occluding configuration and two (one) non-occluding configurations. In the annular tube, for one of the non-occluding configurations, the gas–liquid interface in the middle cross-section of the droplet meets both the inner and outer walls of the tube (bridging configuration); for the other non-occluding configuration, the gas–liquid interface in the middle cross-section of the droplet does not meet the inner wall (non-bridging configuration). The multistability is dependent on the Bond number, the contact angle and the cross-sectional shape. The multistability cannot occur for a zero or very large Bond number. A hydrophilic condition (the contact angle smaller than 90°) contributes to the non-occluding non-bridging configuration, while the hydrophobic condition (the contact angle larger than 90°) contributes to the non-occluding bridging configuration (only for the annular capillary). For the annular capillary with a not-so-large contact angle, increasing the inner-to-outer radius ratio can lead to a larger range of Bond numbers, in which the multistability occurs.

Importance of isoleucine residue in ion channel formation ability of 11-residue peptaibols

Peptaibols are a class of short peptides, typically 7 to 20 amino acids long, characterized by noncanonical amino acid residues such as aminoisobutyric acid (Aib). Although the helix length is shorter than the membrane thickness, the 11-residue peptaibol trichorovin-XII (TV-XII) can form ion channels in membranes. Assuming that a higher proportion of isoleucine (Ile) relative to leucine (Leu) residues is crucial for maintaining the ion channel activity of TV-XII, peptide analogs of TV-XII with varying Ile content were designed, synthesized, and evaluated. The secondary structure of all derivatives under hydrophobic conditions was confirmed by CD measurement as an α-helix-like β-bend ribbon spiral structure. The most stable ion channel activity was found in compound 4a with maximum Ile. Furthermore, the C-terminal Ile analog showed greater ion channel activity compared to the Leu analog. This suggests that the choice between Leu and Ile can influence the expression of ion channel activity, which will be crucial for the de novo designed functional peptides.

Simulating Two-Phase Seepage in Undisturbed Soil Based on Lattice Boltzmann Method and X-ray Computed Tomography Images.

The two-phase seepage fluid (i.e., air and water) behaviors in undisturbed granite residual soil (U-GRS) have not been comprehensively studied due to a lack of accurate and representative models of its internal pore structure. By leveraging X-ray computed tomography (CT) along with the lattice Boltzmann method (LBM) enhanced by the Shan-Chen model, this study simulates the impact of internal pore characteristics of U-GRS on the water-gas two-phase seepage flow behaviors. Our findings reveal that the fluid demonstrates a preference for larger and straighter channels for seepage, and as seepage progresses, the volume fraction of the water/gas phases exhibits an initial increase/decrease trend, eventually stabilizing. The results show the dependence of two-phase seepage velocity on porosity, while the local seepage velocity is influenced by the distribution and complexity of the pore structure. This emphasizes the need to consider pore distribution and connectivity when studying two-phase flow in undisturbed soil. It is observed that the residual gas phase persists within the pore space, primarily localized at the pore margins and dead spaces. Furthermore, the study identifies that hydrophobic walls repel adjacent fluids, thereby accelerating fluid movement, whereas hydrophilic walls attract fluids, inducing a viscous effect that decelerates fluid flow. Consequently, the two-phase flow rate is found to increase with then-enhanced hydrophobicity. The apex of the water-phase volume fraction is observed under hydrophobic wall conditions, reaching up to 96.40%, with the residual gas-phase constituting 3.60%. The hydrophilic wall retains more residual gas-phase volume fraction than the neutral wall, followed by the hydrophobic wall. Conclusively, the investigations using X-ray CT and LBM demonstrate that the pore structure characteristics and the wettability of the pore walls significantly influence the two-phase seepage process.

Molecular Dynamics Simulation of Dual Nanodroplet Impacts on a Cylindrical Surface.

Droplet impact behavior is ubiquitous in various fields. However, the dynamics and spreading mechanisms of micro- and nanoscale droplet impact on curved surfaces, particularly in the case of multiple droplets, have yet to be fully elucidated. In this study, molecular dynamics (MD) methods are employed to investigate the dynamic evolution of double nanodroplet impact on a nano cylindrical wall. The effects of droplet spacing, initial impact velocity, and wall wettability on droplet impact characteristics are analyzed. The results demonstrate that there are five impact modes of nanoscale double-droplet impacts with nanocylinders: spreading-partial wrapping-splitting-complete detachment (SPSC), spreading-complete wrapping-complete attachment (SCC), spreading-partial wrapping-complete attachment (SPC), spreading-partial wrapping-partial attachment (SPP), and spreading-partial wrapping-fragmentation-partial attachment (SPFP). The droplet spacing has an insignificant effect on the impact modes but affects the droplets' spreading shape in both the axial and radial directions. The initial velocity and wall wettability have significant impacts on the droplet impact modes and liquid film spreading characteristics. As the initial velocity increases, the liquid film's radial and axial spreading distances gradually increase. Under hydrophobic conditions, the spreading of the droplet is dominant in the radial direction, while under hydrophilic conditions, the spreading is dominant in the axial direction. Properly reducing the droplet spacing, increasing the impact velocity, and enhancing the wall hydrophobicity can promote detaching the droplet from the cylindrical wall.

Multicomponent image-based modeling of water flow in heterogeneous wet shale nanopores

Shale contains abundant multicomponent nanopores with different wettability. Water flow in multicomponent nanoporous systems is still unclear due to the effects of mineral composition, complex pore-throat topology, and heterogeneous wettability. This work develops a contact angle-dependent numerical model for nanoconfined water flow considering heterogeneous wettability, slip effect, and effective viscosity. Water flow in single-component (i.e., clay, organic, inorganic) and multicomponent nanoporous media reconstructed utilizing image fusion techniques is systematically investigated. Results show that the enhancement factor increases exponentially, and the tortuosity increases with increasing contact angle. Water flow is inhibited under strongly hydrophilic conditions, with the enhancement factor linearly negatively correlated with specific surface area. Under hydrophobic conditions, the throat aspect ratio is inversely related to the enhancement factor, which is suppressed in quasi-circular pores. Water flow is restricted in clay pores and enhanced in organic pores due to the differences in pore-throat size and wettability. For the heterogeneous wetting system, the global flow is enhanced compared to no slip and homogeneous wetting conditions. Affected by clay and organic pores with different wettability, the velocity is non-uniformly enhanced, and the effect diminishes as water flows. This work provides a numerical perspective for water flow in heterogeneous wet nanoporous systems.

Hydrophobicity classification of polymeric insulators using a masked autoencoder model in vision transformer

The loss of hydrophobicity on the polymeric insulator’s surface leads to a continuous water channel formation. This water channel formation can initiate dry band arcing and subsequent flashover. Therefore, accurately identifying the hydrophobicity class is crucial as it provides the surface ageing information of the polymeric insulators. This study proposed a novel approach utilizing a masked autoencoder-based vision transformer image classifier to classify the hydrophobic condition of polymeric insulators accurately. A comprehensive series of tests were conducted on deep learning image classifier models to assess robustness. The experimental findings demonstrated that the vision transformer model exhibited a significant recognition accuracy of 99.69%, surpassing the performance of the CNN, pre-trained CNN, and ViT models.

Toward Effects of Hydrophobicity on Biosurfactant Production by Bacillus subtilis Isolates from Crude-Oil-Exposed Environments

Background: Due to their structural features, biosurfactants reveal promising physicochemical properties, making them interesting for various applications in different fields, such as the food, cosmetics, agriculture, and bioremediation sectors. In particular, the bioproduction of surfactin, one of the most potent microbially synthesized biosurfactant molecules, is of great interest. However, since the wild-type productivities are comparably low, stimulatory environmental conditions have to be identified for improved bioproduction This study aims to find a correlation between the hydrophobicity and production of the biosurfactant surfactin by B. subtilis isolates from crude-oil-contaminated soil and water. Methods: The surfactin production yield was characterized in adapted batch cultivations using high-performance thin-layer liquid chromatography (HPTLC). Defined hydrophobic environmental conditions were achieved by supplementation with hexadecane or polystyrene beads, and the effects on biosurfactant production were measured. Adaptations at the protein level were analyzed using mass spectrometry measurements. Results: The correlation between hydrophobicity and surfactin production was characterized using Bacillus subtilis strains ZH1 and P7 isolated from crude-oil-contaminated soil and water. Since these isolates show the biodegradation of crude oil and hexadecane as hydrophobic substrates, respectively, a first-time approach, using polystyrene beads, was applied to provide a hydrophobic environment. Interestingly, contrary to popular opinion, reduced biosurfactant production was determined. Using mass spectrometric approaches, the physiological effects of co-cultivation and the cellular response at the protein level were investigated, resulting in altered quantities of stress proteins and proteins involved in the carbon metabolism counter to polystyrene beads. Conclusions: Contrary to common opinion, increasing hydrophobicity does not have a stimulating effect, and even reduces the effect on the bioproduction of surfactin as the main biosurfactant using selected B. subtilis strains.

Retention mechanism on phosphodiester stationary phases in hydrophilic interaction liquid chromatography and purely aqueous mobile phase part II: Overloading with limited soluble samples

The adsorption behaviour of caffeine and theophylline under hydrophilic interaction chromatography and purely aqueous conditions was investigated on four phosphodiester stationary phases. Solute adsorption isotherms were determined by frontal analysis or inverse method. The bi-Langmuir model was found to be the best choice to describe the behaviour of caffeine and theophylline adsorption in purely aqueous conditions, whereas the bi-Moreau model describes the adsorption phenomena in HILIC conditions. The results obtained demonstrate that the interaction of caffeine and theophylline with the stationary phase surface varies depending on the mobile phase composition. Both in pure aqueous mobile phase and in HILIC mode, the heterogeneity of the surface of the studied stationary phases is confirmed. In hydrophilic solutions, the sample molecules interact with the stationary phase only. In hydrophobic conditions, a lateral interaction occurs between caffeine or theophylline molecules, which are poorly soluble in acetonitrile-rich solvents. This confirms that the same compound on the same stationary phase can behave rather differently, depending on the mobile phase composition. Thus, the mobile phase may govern and control the retention mechanism.

Vanillin derived partially bio-based benzoxazine resins for hydrophobic coating and anticorrosion applications: Studies on syntheses and thermal behavior

ABSTRACT The study mainly focuses on the synthesis, thermal, hydrophobic, and anticorrosion properties of environmentally friendly polybenzoxazines based on vanillic acid for applications such as water repellent coatings and anticorrosion. Vanillic acid (VA) was individually reacted with cyclohexylamine (cha), dodecylamine (dda), furfurylamine (ffa), and 3-trifluoromethylaniline (tfma) in order to develop structurally distinct benzoxazines. The synthesized monomers molecular structure was examined using ATR-FTIR and 1H-NMR. Thermal characteristics were also described using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polymerization temperature (Tp) of benzoxazines synthesized was observed in the range of 203–245°C from DSC analysis. The polymerization temperature of VA-ffa was found to be 203°C, which has lower than that of other benzoxazine monomers. Typically, the early decomposition temperatures of all the developed polybenzoxazines were over 250°C, demonstrating remarkable thermal stability. Poly(VA-tfma), one of the polybenzoxazines, exhibits highest value of char yield of 43% at 850°C. Additionally heat resistance index obtained for all the polybenzoxazines was ranged between 147 and 158°C. The value of water interface angle noticed for polybenzoxazine ranges from 142° to 145°. Among the synthesized polybenzoxazines, poly(VA-tfma) showed excellent hydrophobicity with highest value of 145°. In addition, hydrophobicity of the benzoxazine coated cured cotton fabric was analyzed for its durability at various time intervals. SEM analysis was performed for all the four VA-based polybenzoxazines. Benzoxazines were coated on mild steel (MS) plates to study the corrosion resistant property. Poly(VA-tfma) has better corrosion resistant behavior than that of poly(VA-cha), poly(VA-dda) and poly(VA-ffa) according to electrochemical impedance measurements. Further, salt spray test was conducted on polybenzoxazine coated MS for 96 h, minimum weight loss was observed for initial and after 96 h. Data from several studies indicate that benzoxazine, which is based on vanillic acid, can be utilized for applications demand hydrophobic condition with corrosion protection.

Computational study of bubble, thin-film dynamics and heat transfer during flow boiling in non-circular microchannels

Flow boiling in multi-microchannel evaporators is one of the most efficient thermal management solutions for high-power-density applications. However, there is still a lack of understanding of the governing two-phase heat and mass transfer processes that occur in these devices, which has resulted in a limited availability of applicable boiling heat transfer prediction methods based on first principles, and of reliable thermal design tools. This article presents a systematic analysis of the dynamics of bubbles and the surrounding liquid film during flow boiling in three-side-heated non-circular microchannels. The study is performed using a custom version of ESI OpenFOAM v2106 with a geometric volume-of-fluid method to capture the interface dynamics, also incorporating conjugate heat transfer through the evaporator walls. The hydraulic diameter of the channel is fixed to Dh=0.229mm and the range of width-to-height aspect ratios ϵ=0.25−4 is examined. We investigate different fluids, namely water, HFE7100, R1233zd(E), R1234ze(E), and evaporator materials, namely copper, aluminium, silicon, stainless steel, with base heat fluxes in the range qb=50−200kW/m2. The results show that conjugate heat transfer acts to make the temperature distributions around the perimeter of the channel cross-section more uniform, and that the topography of the lubricating film and the extension of the dry vapour patches that develop while the film is depleted both depend on the cross-sectional channel shape and influence the heat transfer performance significantly. For highly wetting conditions, channels with ϵ=0.25 tend to allow enhanced heat transfer rates, with a spatially-averaged Nusselt number that is 50% higher than that obtained for ϵ=1 (square channels) and 10% higher than that for ϵ=4. This arises thanks to an extended evaporating film that covers the vertical walls which, owing to the three-side-heated configuration, contribute twice to the spatially-averaged heat transfer performance. For more hydrophobic conditions, large dry patches develop over the vertical walls for ϵ=0.25 due to the lower evaporator temperatures, leading to reduced heat transfer, with thermal performance weakly dependent on ϵ in the range ϵ=0.5−2.

A biomimetic design for efficient petrochemical spill disposal: CoFe-PBA modified superhydrophobic melamine sponge with mechanical/chemical durability and low fire risk

Due to frequent petrochemical spills, environmental pollution and the threat of secondary marine fires have arisen, necessitating an urgent need for petrochemical spill treatment strategies with high-performance oil-water separation capabilities. To address the challenges of poor durability, instability in hydrophobic conditions, and difficulty in absorbing high-viscosity crude oil associated with hydrophobic absorbent materials, the authors of this study took inspiration from the unique micro and nanostructures of springtails' water-repellent skin. We engineered a superhydrophobic melamine sponge using interfacial assembly techniques designated as Si@PBA@PDA@MS. This material demonstrated improved mechanical and chemical durability, enhanced photothermal performance, and reduced fire risk. The metal-organic framework (MOF)-derived cobalt-iron Prussian blue analog (CoFe-PBA) was firmly anchored to the sponge framework by the chelation of cobalt ions using polydopamine (PDA). The results demonstrated that Si@PBA@PDA@MS demonstrated excellent superhydrophobicity (WCA=163.5°) and oil absorption capacity (53.4–97.5 g/g), maintaining high durability even after 20 cycles of absorption-squeezing. Additionally, it could still exhibit excellent mechanical properties, hydrophobic stability, and absorption performance across a wide temperature range (0–100 °C), pH range (1−14), and high compression strength (ε = 80%), with excellent mechanical/chemical durability. Furthermore, Si@PBA@PDA@MS demonstrated remarkable photothermal performance and low fire risk, offering efficient, safe, and sustainable practical value for effective petrochemical spill treatment.

Influence of vibration on droplet dynamics in a three-dimensional porous medium

In this study, the effects of vibration on droplet dynamics inside a three-dimensional (3D) porous medium are investigated with a focus on frequency, amplitude, and surface wettability. A lattice Boltzmann method based on the Allen–Cahn equation (A-C LBM) is used. The results show that the volume of the drained drop and drainage duration of the droplet are significantly affected by the contact angle. The hydrophilic nature of the pores causes the droplet to spread inside the medium and resist the vibration force, resulting in a lower discharged liquid volume and delayed drainage. In contrast, a hydrophobic surface repels the droplet and leads to quicker drainage. It is also observed that the speed of droplet drained from the porous medium is higher for hydrophobic conditions, causing the separated drop to rebound and jump back toward the medium after impacting the surrounding wall boundaries. A thorough investigation is conducted on the combined implication of the surface adhesion, amplitude, and frequency of vibration on the first separation time of the droplet from the porous medium and full drainage duration. The results show that with increasing the hydrophobicity, the required vibration amplitude for complete drainage has decreased. In this way, the interplay between the adhesive force and the vibration force impedes the liquid phase separation from the hydrophilic porous medium at a low vibration amplitude. However, the results demonstrate that even in these conditions, an increase in the vibration frequency can enhance the separation and improve the drainage of the liquid phase from the pores.

Purification of antibacterial attacins induced in Hyalophora cecropia pupae immunized with Enterobacter cloacae C7‐501 using ion‐exchange chromatography, hydrophobic interaction chromatography, and Rotofor® isoelectric focusing

AbstractHyalophora cecropia pupae were infected by Enterobacter cloacae C7‐501 to induce antibacterial attacins for purification. The induction of attacins in immunized pupae was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Ion‐exchange chromatography (IEC), hydrophobic interaction chromatography (HIC), and Rotofor® isoelectric focusing (ISEF) were applied to isolate attacins from the hemolymph. IEC separated attacins from most hemolymph proteins, but the fractions containing attacins also had other proteins of 20 and 64 kDa in length. In IEC, attacin was eluted with ~0.2 M NaCl. The best conditions for IEC were pH 9, flow rate of 2 mL/min, with step elution (0.025, 0.05, 0.075, 0.1, 0.2, 0.4 and 1.0 M NaCl). In HIC, most other proteins were eluted with the ammonium persulfate treatment. HIC isolated attacin proteins under hydrophobic conditions, at ~50% EtOH. However, the fraction with attacins also contained other proteins. The Rotofor® ISEF produced fractions containing attacins at isoelectric points ranging between 5.7 and 8.3. However, non‐specific proteins were detected in the fraction samples, and the recovery of attacins was low. The purification efficiency of ISEF was lower than IEC and HIC. In this study, the expression of attacins was induced in H. cecropia pupae infected with E. cloacae C7‐501, and attacins could be purified by IEC and ISEF. Overall, IEC provided better separation of attacins from the hemolymph of H. cecropia pupae immunized with E. cloacae bacteria than HIC and Rotofor® ISEF.

Optimization of concentration and exposure time of polytetrafluoroethylene (PTFE) for the development of hydrophobic coating of drying chamber of spray dryer

Modelling was applied using response surface methodology (RSM) and central composite rotatable design (CCRD) in order to establish the optimum conditions for applying PTFE on borosilicate glass to create a hydrophobic surface coating. Two experimental operating conditions of concentration and exposure time of polytetrafluoroethylene (PTFE) were optimized, obtaining high contact angle value, and showed high hydrophobic characteristics for PTFE-coated plate. Multiple linear regression analysis was implemented to develop a second-order polynomial model for the response. Results indicated that the most significant (p<0.05) factors influencing the contact angle value of the PTFE-coated plate were the main effect of concentration of PTFE. When the PTFE concentration increases, the plate’s contact angle also increases. The optimum conditions to maximize the value of contact angle (113.23°) for hydrophobic characteristics were a PTFE concentration of 9.17% and a PTFE exposure time of 6 minutes. The experimental results met what was predicted, indicating the model suitability for hydrophobic conditions optimization for the plate. This research indicated a good optimization of a PTFE solution in developing hydrophobic surface on a PTFE-coated plate.

Interfacial thermal resistance calculations for weak solid–liquid atom interactions using equilibrium molecular dynamics

ABSTRACT This study investigates the use of equilibrium molecular dynamics (EMD) simulations for determining interfacial thermal resistance (ITR) at solid-liquid interfaces. The Green-Kubo theorem is typically used for this purpose, but it may not be suitable for hydrophobic conditions where the interaction between liquid and solid atoms is weak. Two EMD simulation methods were used to calculate ITR at interfaces under different wetting conditions: one using instantaneous temperature differences and the other using instantaneous heat flux. The data derived from the EMD simulation using instantaneous temperature difference could not converge due to weak intermolecular interactions, leading to inaccurate ITR calculations. To address this issue, a method for calculating ITR in the frequency domain is proposed. Results showed that both EMD methods produced different results from non-equilibrium molecular dynamics (NEMD), with the ITR of EMD using instantaneous heat flux being higher than that of NEMD, while the ITR of EMD using instantaneous temperature was lower, and in good agreement with NEMD. Overall, this study highlights the limitations of using EMD simulations for calculating ITR at solid-liquid interfaces in hydrophobic conditions and proposes a new method for improving accuracy in these situations.

Pore-scale modeling of pore structure properties and wettability effect on permeability of low-rank coal

Permeability is a key parameter for coalbed methane development. Although the absolute permeability of coal has been extensively studied, wettability and pore structure properties continue to challenge the microscopic description of water-gas flow in coal. For this purpose, we reconstructed the microstructures of low-rank coal using micro-computed tomography (micro-CT) images. Pore geometry and pore-throat parameters are introduced to establish a relationship with absolute permeability. A dual-porosity pore network model is developed to study water-gas displacement under different wetting and pore structure properties. Results show that absolute permeability is significantly affected by pore geometry and can be described using a binary quadratic function of porosity and fractal dimension. Water-gas relative permeability varies significantly and the residual gas saturation is lower; the crossover saturation first decreased and then increased with increasing porosity under hydrophobic conditions. While the water relative permeability is lower and a certain amount of gas is trapped in complex pore-throat networks; the crossover saturation is higher under hydrophilic conditions. Models with large percolating porosity and well-developed pore networks have high displacement efficiency due to low capillary resistance and avoidance of trapping. This work provides a systematic description of absolute permeability and water-gas relative permeability in coal microstructure for enhanced gas recovery.

Experimental investigation of the effect of hydrophobic coating on heat transfer and gasketed plate heat exchanger performance

In this study, the effect of hydrophobicity on the plate surface on heat transfer, pressure drop, and pump power was investigated without changing the existing designs of gasketed plate heat exchangers (GPHEs). The wet surfaces of the plate were coated with carbon-based polymer solutions with four different hydrophobic groups, that is, FEP, FH3, FH7, and FH10. To increase the hydrophobicity of the FEP material, a new coating solution was synthesized by adding 3, 7, and 10 wt.% h-BN nanoparticles. Heat transfer, pressure loss, and pump power performances of heat exchangers with hydrophobic surface coating were tested at five different Reynolds numbers and compared with the uncoated heat exchanger performance. Also, the efficiency analysis of the GPHE under different hydrophobic conditions was carried out. As a result, the addition of 3 and 7 wt.% h-BN nanoparticles increased the contact angle. However, the addition of 10 wt.% h-BN decreased the contact angle as it increased the rough structure and film thickness on the surface. It was determined that the heat exchanger efficiency increased proportionally with the increase in hydrophobicity. While the highest heat exchanger efficiency value was 0.525 in FH7 coated. However, it was found that there was a 25.6% decrease in heat transfer of FH7 coating compared to uncoated exchanger. The pressure drop of the FH7 surface-coated heat exchanger with the highest hydrophobicity was 207.6% lower than that of uncoated heat exchanger. Energy savings of approximately 41% were achieved in FH7 coated compared to uncoated heat exchangers. It has been emphasized that heat transfer in GPHE systems should be evaluated together with pressure drops and local losses. It was found that the use of hydrophobic surface coating on plates in heat exchangers will contribute to the development of heat exchanger designs, reducing pump costs, and energy consumption.

Entropy generation and forced convection analysis of ethylene glycol/MWCNTs-Fe3O4 non-Newtonian nanofluid in a wavy microchannel with hydrophobic surfaces

BackgroundA three-dimensional simulation has been conducted to study the impact of the hydrophobicity of surfaces on heat transfer, hydrodynamics, and entropy generation of a non-Newtonian nanofluid in a wavy microchannel. MethodsThe hybrid nanofluid is composed of ethylene glycol/MWCNTs-Fe3O4, and the wavy surface is under a constant heat flux. The main parameters that have been studied in this research are 10≤ Re ≤150, 1.25% ≤ φ ≤1.8%, and 0 ≤ β* ≤0.1. The effects of the mentioned parameters during the research on velocity and temperature distribution, forced convection, pressure drop, and entropy generation have been investigated in detail. The outcomes indicated that using hydrophobic boundary conditions leads to an increase in heat transfer and a decrease in pressure losses, which is useful for the efficiency of cooling systems. The results also show that although increasing the volume fraction of nano-additives and Reynolds number leads to an increment in cooling, they also increase the pressure drop. Significant findingsThe PEC and relative entropy generation results are studied for finding the optimized points.

Naturally Derived Cements Learned from the Wisdom of Ancestors: A Literature Review Based on the Experiences of Ancient China, India and Rome.

For over a thousand years, many ancient cements have remained durable despite long-term exposure to atmospheric or humid agents. This review paper summarizes technologies of worldwide ancient architectures which have shown remarkable durability that has preserved them over thousands of years of constant erosion. We aim to identify the influence of organic and inorganic additions in altering cement properties and take these lost and forgotten technologies to the production frontline. The types of additions were usually decided based on the local environment and purpose of the structure. The ancient Romans built magnificent structures by making hydraulic cement using volcanic ash. The ancient Chinese introduced sticky rice and other local materials to improve the properties of pure lime cement. A variety of organic and inorganic additions used in traditional lime cement not only changes its properties but also improves its durability for centuries. The benefits they bring to cement may also be useful in enzyme-induced carbonate precipitation (EICP) and microbially induced carbonate precipitation (MICP) fields. For instance, sticky rice has been confirmed to play a crucial role in regulating calcite crystal growth and providing interior hydrophobic conditions, which contribute to improving the strength and durability of EICP- and MICP-treated samples in a sustainable way.