Surface Condensation Research Articles

Actin polymerization counteracts prewetting of N-WASP on supported lipid bilayers

Cortical condensates, transient punctate-like structures rich in actin and the actin nucleation pathway member Neural Wiskott-Aldrich syndrome protein (N-WASP), form during activation of the actin cortex in the Caenorhabditis elegans oocyte. Their emergence and spontaneous dissolution is linked to a phase separation process driven by chemical kinetics. However, the mechanisms that drive the onset of cortical condensate formation near membranes remain unexplored. Here, using a reconstituted phase separation assay of cortical condensate proteins, we demonstrate that the key component, N-WASP, can collectively undergo surface condensation on supported lipid bilayers via a prewetting transition. Actin partitions into the condensates, where it polymerizes and counteracts the N-WASP prewetting transition. Taken together, the dynamics of condensate-assisted cortex formation appear to be controlled by a balance between surface-assisted condensate formation and polymer-driven condensate dissolution. This opens perspectives for understanding how the formation of complex intracellular structures is affected and controlled by phase separation.

Comportamento higrotérmico de tijolo cerâmico de olaria do sul do Brasil

Abstract The presence of moisture in buildings can lead to pathological manifestations, and the behavior of materials when exposed to various conditions can be predicted through computational simulations. For this purpose, the hygrothermal characteristics of building elements are paramount. In Brazil, there is a gap in studies on the hygrothermal properties of materials, compromising simulations. This article discusses the possibilities of using European data in simulating moisture transport in ceramic brick walls in the southern region of Rio Grande do Sul, Brazil. The results were generated by comparing hygrothermal simulations with WUFI Pro 6.5 using the simulation program database with data collected from laboratory tests on ceramic bricks from a southern Brazilian brickyard. Tests for water vapor diffusion resistance, water absorption, and hygroscopic curves were conducted. Although both situations led to the growth of filamentous fungi, experimental data led to3% lower values compared to database results. Regarding surface condensation, a likely higher occurrence was observed when using laboratory test data.

Pyramid floating solar still with enhanced condensation surfaces operating under actual weather conditions

The potential solution offered by floating solar still (FSS) to water scarcity confronts challenges associated with condensate droplet loss and structural instability under oceanic and swaying condition. A novel pyramid FSS with reduced wettability surfaces (silicon nano-coated) was proposed, utilizing central symmetry structure of pyramid to reinforce the stability and adopting nano-coated surfaces to enhance the condensation. A 4-day outdoor experiment was conducted to evaluate the performance. The highest yield of nano-coated FSS was 1.017 kg/m2/d under an accumulated irradiation of 15.166 MJ/m2/d, which was 16.76% higher than that of uncoated FSS. Furthermore, the yield of nano-coated FSS was 0.949 kg/m2/d in the river experiment, showing a significant improvement. Next, the enhancement of nano-coated surface on droplet collection was numerically analyzed, showing that the condensation droplets could retain their complete shape until detachment. In contrast, the detachment process on the uncoated surface involved a separation of neck, leaving a residue of liquid behind. Quantitative analysis showed longer movement distances and faster travel velocities for droplets on the nano-coated surface, and these two improvements could facilitate condensate collection. Furthermore, the cost analysis reveals a CPL of 0.129 $/L for the proposed FSS, suggesting its affordability for off-grid communities.

Charge‐Mediated Interactions Affect Enzymatic Reactions in Peptide Condensates

AbstractBiomolecular condensates, formed through liquid‐liquid phase separation (LLPS), serve as enzymatic reaction centers in cells by increasing local concentrations of enzymes and substrates, thereby facilitating reaction kinetics and regulatory mechanisms. Inspired by these natural systems, synthetic condensates are being developed for diverse applications, including payload delivery, sensing, and as microreactors where enzymatic reaction kinetics can be modulated by factors like pH, viscosity, and enzyme‐substrate co‐localization. Here, we investigate how the physicochemical properties of enzymes and substrates influence condensate formation and function as microreactors. Focusing on cellulase and alkaline phosphatase, which differ in molecular weight and isoelectric point, we employed a minimalistic complex coacervation system of oppositely charged LLPS‐promoting peptides. Our findings show how electrostatic forces within condensates influence their role as microreactors. Specifically, the ability of condensates to encapsulate or exclude phosphatase, cellulase, and their substrates, which is pivotal for the regulation of reaction kinetics, is determined by the enzyme surface charge, substrate charge, and condensate charge stoichiometry. These results highlight the potential of utilizing electrostatic forces within condensates to modulate enzymatic reactions, providing critical insights for developing synthetic condensates as microreactors in biotechnology and materials science.

Large eddy simulation of soot formation in a turbulent lifted flame with a discretized population balance and a reduced kinetic mechanism

This article presents simulations of a turbulent lifted flame using the large eddy simulation-transport probability density function-discretized population balance equation approach. This approach takes into account the interaction between turbulent reacting flow and soot particle formation. A reduced chemical kinetics mechanism including a series of polycyclic aromatic hydrocarbons (PAHs) species linked to soot formation is generated employing the approach of the directed relation graph error propagation and is tested on a perfectly stirred reactor under varying equivalent ratio conditions and premixed flames. The soot kinetics model includes the PAH-based nucleation and surface condensation, the hydrogen abstraction acetylene addition surface growth and oxidation mechanism, and the size-dependent aggregation. The soot morphology considers the surface area and other geometrical properties for both spherical primary particles and fractal aggregates. The simulation results show, in general, reasonably good agreement with experimental measurements in terms of lifted height, flame shape, flow-field velocity, the hydroxyl radical, and soot volume fraction. A discussion of micromixing and its modeling in the context of the Interaction by Exchange with the Mean model is also presented. To investigate the effect of the soot micromixing frequency factor on soot particles, an additional simulation is conducted where this factor is reduced by a factor of 10 for the soot particles. The maximum soot volume fraction is observed to increase slightly. However, compared with the impact of kinetics on soot modeling, this effect is a minor one.

Frost crystal growth behavior on a hydrophilic surface over a wide range of cold surface temperature

The initial frosting phenomenon is a discontinuous phase nucleation process, the cold surface temperature and properties have a decisive influence on this phenomenon, especially in the initial frosting stage. With the development of aerospace and energy transportation technology, frost formation at low temperatures (-100 °C∼-30 °C) and ultra-low temperatures (-273 °C∼-100 °C) has gradually attracted the attention of researchers. In this paper, the initial frosting phenomena on hydrophilic surfaces with a contact angle of 10° (CA= 10°) and ordinary (CA= 95°) surfaces are studied experimentally in a wide range of cold surface temperatures (-190 °C∼-30 °C). Four modes are confirmed: cold surface condensation frosting, cold surface sublimation frosting, air boundary layer condensation frosting and air boundary layer sublimation frosting. It is also found that the four frosting modes do not appear in turn with the decrease of the cold surface temperature, but two or more frosting modes appear at the same time. And the surface contact angle has an important influence on the frosting mode. The initial frost crystal morphology mainly depends on the cold surface temperature and the corresponding frosting mode. Four different forms of frost crystals are observed: hexagonal prism (feather), branch (pine needle), cluster (shrub) and floc (grape), in which the cluster frost crystal is more sensitive to the surface contact angle and can appear in different temperature ranges due to different contact angles. Based on the statistics of the size, quantity, and distribution of the initial frost crystals, it is found that -70 °C is a major turning point for frost formation from the cold surface sublimation frosting to the air boundary layer sublimation frosting, and an important change has taken place near this point. Furthermore, it affects the shape and size distribution of frost crystals. These findings are of great significance for the study and understanding of frost crystal growth mechanism in the initial stage of frost formation at low and ultra-low temperatures.

Micrometer Groove Array Structures Inspired by Desert Grasses on Curved Substrates for Enhanced Surface Condensation Efficiency.

Drawing inspiration from the microstructures on biological surfaces to create highly efficient water-collecting surfaces is an effective way to address water scarcity. Inspired by the role of the convex and concave grooves on the surface of Namib desert grass in promoting condensation, we show that optimizing the curvature radius improves the condensation rate of droplets. This convex-concave geometry, combined with nanoneedle structures on the groove ridges, facilitates droplet merging and self-removal through jumping, refreshing the condensation site and further enhancing condensation efficiency. Meanwhile, reducing the adhesive resistance in the groove valleys accelerates droplet migration and removal. We believe this design strategy can be applied to a wide range of water collection and phase change heat transfer applications.

Biomimetic fractal pillars for the thermal–hydraulic enhancement of a vapor chamber

Owing to their remarkable thermal–hydraulic performance, vapor chambers have diverse applications, especially for cooling electronic devices. However, the performances of circular and noncircular pillars throughout the entire vapor chamber under identical wick volume conditions have been compared in very few studies. In this study, a series of noncircular pillar arrays featuring biomimetic tree-like fractal networks is introduced. The incorporation of fractal pillars significantly enhances the thermal–hydraulic performance of the vapor chamber because the gas–liquid interface area is extended. Compared to a vapor chamber with circular pillars, the maximum condensation surface temperature difference, total thermal resistance, and liquid pressure drop of this vapor chamber with fractal pillars are reduced by up to 57.8 %, 13.8 %, and 10.9 %, respectively. In particular, with large branch levels and pillar diameters, the fractal structure is pivotal for boosting the overall performance. When the number of pillars is increased, the fractal structure's impact on the thermal performance reaches a limit, whereas its boosting effect on the flow performance weakens. This study is a pioneering exploration of the application of stretched geometries in pillar-type vapor chambers, with fractal pillars utilized in showcase demonstrations.

Thermal performance and energy efficacy of membrane-assisted radiant cooling outdoors

Membrane-assisted radiant cooling systems offer a promising solution for directly cooling human bodies in outdoor settings. In this study a prototype system is experimentally assessed, which comprised of two wall-mounted panels and one ceiling-mounted panel with the cooling provided by a water chiller system. Three different radiant panel surface temperatures (Tsur =14.3°C, 17.8°C, 21.9°C) were tested to observe possible condensation and to measure the heat flux, and a thermal comfort survey was conducted in combination to analyze the system energy efficacy. The results indicate that selecting appropriate panel surface temperatures under different ambient universal thermal climate index (UTCI) conditions can not only effectively avoid energy surplus but also improve thermal comfort for people. When the ambient UTCI is 38.1°C, the panel surface temperature needs to be lowered to 14.3°C to achieve neutral thermal sensation while 333.7 W of cooling energy is required; but when the ambient UTCI is 29.9°C, a panel surface temperature of 21.9°C would suffice with a much lower energy demand. It is also concluded that the surface condensation may occur but can be controlled. This experimental study provides solid data for the further development of radiant cooling technology for open-space applications.

Corrosion at Top-of-the-Line in High Pressure and Dense CO2 Environments

This study presents unique data on top-of-the-line corrosion (TLC) occurring in high-pressure environments where CO2 was in the gaseous, liquid, or supercritical state. While CO2 is traditionally in a gaseous phase, this form of degradation is referred to as TLC. In this study, similar phenomena with different mechanisms were observed in liquid CO2 and supercritical states all of which are referred to as TLC due to the location of specimens and ease of comprehension. Experiments were conducted to investigate the effect of CO2 partial pressure (ranging from 20 bar to 100 bar) with temperatures (30°C to 50°C) relating to different water condensation rates (0.001 mL/m2/s to 0.1 mL/m2/s). Uniform and localized TLC rates increased with a higher water condensation rate and surface temperature. As long as CO2 remained gaseous, its partial pressure (pCO2) showed a negligible influence on both uniform and localized TLC rates. At the highest gaseous CO2 content tested, the formation of a protective iron carbonate (FeCO3) layer decreased the TLC rate, with this effect being more pronounced at lower water condensation rates. The risk of localized corrosion for specimens exposed to this environment at high and medium water condensation rates remained an issue. In the dense phase CO2 environment, the difference in temperature between the bulk environment and the specimen’s surface caused a similar phenomenon to water condensation, termed water drop-out, which resulted in corrosion. The rate of water drop-out could not be measured experimentally or estimated theoretically but is a complex function of temperature, pCO2, and CO2 physical state. The interplay between high pCO2 and low pH of the dropped-out water led to elevated uniform and localized corrosion rates. The depth of localized corrosion, at the high and medium water drop-out conditions, reached its maximum at the surface temperature of ca. 45°C. At a lower surface temperature of ca. 25°C and a higher surface temperature of ca. 65°C, the maximum penetration rate was decreased due to slower kinetics of reactions and the formation of a more protective FeCO3 layer, respectively. The results presented in this study highlight the significant difference between corrosion rates, especially in the form of localized damage, in gaseous and dense-phase CO2 environments.

Interplay of condensate material properties and chromatin heterogeneity governs nuclear condensate ripening.

Nuclear condensates play many important roles in chromatin functions, but how cells regulate their nucleation and growth within the complex nuclear environment is not well understood. Here, we report how condensate properties and chromatin mechanics dictate condensate growth dynamics in the nucleus. We induced condensates with distinct properties using different proteins in human cell nuclei and monitored their growth. We revealed two key physical mechanisms that underlie droplet growth: diffusion-driven or ripening-dominated growth. To explain the experimental observations, we developed a quantitative theory that uncovers the mechanical role of chromatin and condensate material properties in regulating condensate growth in a heterogeneous environment. By fitting our theory to experimental data, we find that condensate surface tension is critical in determining whether condensates undergo elastic or Ostwald ripening. Our model also predicts that chromatin heterogeneity can influence condensate nucleation and growth, which we validated by experimentally perturbing the chromatin organization and controlling condensate nucleation. By combining quantitative experimentation with theoretical modeling, our work elucidates how condensate surface tension and chromatin heterogeneity govern nuclear condensate ripening, implying that cells can control both condensate properties and the chromatin organization to regulate condensate growth in the nucleus.

Theoretical and experimental analysis of evaporative cooling with hydrophilic screen mesh on condenser surface

In this study, we theoretically and experimentally analyzed the effect of evaporative cooling on the external thermal resistance of a condenser with a water-filled hydrophilic screen mesh. To calculate the external thermal resistance of the condenser theoretically, the external thermal resistance model was developed, considering evaporative cooling in the screen mesh. The evaporative mass flow rate in the screen mesh was calculated using the Lewis number, which can convert heat transfer to mass transfer. Especially, the maximum flow rate absorbed by the screen mesh was theoretically determined by the capillary limit. In experimental approach, hydrophilic screen meshes with mesh numbers M100, M150, and M200 were manufactured and attached to an aluminum plate simulating the condenser surface. The external thermal resistance of the condenser was measured. Based on the results, the theoretical model was well matched with experimental results. The effects of the air velocity, mesh number, and heat flux on the external thermal resistance of the condenser with evaporative cooling in the water-filled hydrophilic screen mesh were investigated. Finally, it is shown that the external thermal resistance of the condenser with evaporative cooling using the water-filled hydrophilic screen mesh can be reduced up to an average of 92 %.

Heat transfer performance of the vapor chamber with spiral support-composite wick

Inefficient heat dissipation in vapor chambers (VCs) is a major challenge for their development and application. To investigate the effect of supports on VCs’ maximum thermal power and thermal resistance, the relationship between the number of supports and the vapor channel pressure drop is studied through pressure drop measurement. Composite Wick Vapor Chambers (CWVCs) with various supports are fabricated and tested with a constructed thermal performance test platform. The results indicate that the heat transfer performance of CWVC is related to the number of supports and the liquid filling ratio. The optimum filling ratio of the composite wick with 3-6 spiral supports (SS3-SS6) is 60%, 70%, 90%, and 70%, with corresponding maximum thermal power of 19.25 W, 25.61 W, 25.97 W, and 21.22 W. The thermal resistance of SS4-CWVC is lower overall. Additionally, when the power is 21 W, the surface temperature difference of the condenser of SS3-CWVC and SS6-CWVC is 2.3 °C and 1.3 °C, respectively. However, the condenser surface temperature difference of SS4-CWVC is 66.5% lower than that of SS3-CWVC and 40.8% lower than that of SS6-CWVC at the same power. Therefore, SS4-CWVC exhibits better temperature uniformity and has better heat transfer performance.

Laser Interference Additive Manufacturing: Mask Bundle Shape Bionic Shark Skin Structure.

Here, we explored a new manufacturing strategy that uses the mask laser interference additive manufacturing (MLIAM) technique, which combines the respective strengths of laser interference lithography and mask lithography to efficiently fabricate across-scales three-dimensional bionic shark skin structures with superhydrophobicity and adhesive reduction. The phenomena and mechanisms of the MLIAM curing process were revealed and analyzed, showing the feasibility and flexibility. In terms of structural performance, the adhesive force on the surface can be tuned based on the growth direction of the bionic shark skin structures, where the maximum rate of the adhesive reduction reaches about 65%. Furthermore, the evolution of the directional diffusion for the water droplet, which is based on the change of the contact angle, was clearly observed, and the mechanism was also discussed by the models. Moreover, no-loss transportations were achieved successfully using the gradient adhesive force and superhydrophobicity on the surface by tuning the growth direction and modifying by fluorinated silane. Finally, this work gives a strategy for fabricating across-scale structures on micro- and nanometers, which have potential application in bioengineering, diversional targeting, and condenser surface.

Maximizing the wetting resistance of fluorine-free omniphobic membranes for hypersaline wastewater desalination

Membrane distillation (MD) equipped with omniphobic (non-wetting) membranes has found a niche in water reclamation from hypersaline industrial wastewater. Here, we examined the efficacy of non-fluorinated materials as surface coating agents for omniphobic MD membrane fabrication, and identified necessary mechanisms to attain a maximized wetting resistance using fluorine-free materials. We first prepared MD membranes with different surface chemistries using a series of linear alkylsilanes and polydimethylsiloxane (PDMS) as representative fluorine-free, low surface energy materials. Membranes modified with a longer chain alkylsilane exhibited a lower surface energy and demonstrated a greater wetting resistance in direct contact MD experiments using feedwaters of various surface tensions. Despite the nearly identical surface energy measured for the longest alkylsilane and PDMS, PDMS-modified membrane exhibited an extended antiwetting performance as compared to the membrane treated with the longest alkylsilane. To elucidate the source of the distinctive wetting resistance, we examined the nucleation and condensation kinetics on the surfaces with the different surface chemistries via environmental scanning electron microscopy. Our analysis suggests that the membranes treated with long chain alkylsilanes contain surface defects (i.e., hydrophilic regions) whereas the high mobility of the PDMS effectively minimizes the defect exposure, slowing down the condensation and subsequent surface wetting.

Investigating condensation from humid air under mixed convection regime

A wide range of industrial applications rely heavily on heat transfer during vapor condensation from a mixture of water vapor and noncondensable gases (NCG). For a vertically-mounted condenser plate, the vapor-diffusion boundary-layer thickness is influenced by the interplay of the thermogravitational and forced flow fields, eliciting classical mixed convection scenario. This thickness in turn dictates the condensation heat and mass transfer rates. While condensation in presence of NCG under free and forced convection scenarios are well-characterized in the literature, its counterpart in the mixed convection regime is relatively uncharted. Herein, condensation from an upward stream of humid air over a vertically mounted mild steel condenser surface is characterized under different flow velocities. The free-stream flow is thus directed opposite to the thermogravitational flow induced next to the plate. We observe that with increasing the magnitude of the upward flow velocity of the free stream, the condensation heat transfer coefficient (CHTC) initially decreases until it reaches a minimum at 0.4 m/s, beyond which the CHTC rises again with the flow velocity. Using the Nusselt analogy for mixed convection for the relevant flow regimes we substantiate our experimental findings and extend the observation for predicting condensation behavior under different experimental ambient conditions.

Preparation of a moisture-permeable glazed tile to prevent indoor floor condensation

Condensation would occur on smooth tiled floors during the period from winter to spring after rainy or continuous wet days in the hot-humid climate. It is an effective passive approach to use moisture-permeable tiles for mitigating surface condensation on indoor floors. This study proposes a moisture-permeable glazed tile prepared by the conventional tile-making process. The base tile of the proposed glazed tile is primarily composed of kaolin, quartz and feldspar, with addition of soluble starch as a pore-forming agent before firing. The glaze layer is formed by spraying a slurry which is a mixture of a low-temperature glaze and the pore-forming agent (soluble starch). The present study investigated the impact of the pore-forming agent ratio on tile porosity, wet capacity, breaking strength, moisture permeability, and abrasion resistance. It was found that the increase of the pore-forming agent ratio in the base tile can enhance the porosity and moist capacity of the base tile, and weaken the breaking strength. Moreover, the increase of the pore-forming agent in the glaze can improve moisture permeability of the glaze and reduce abrasion resistance. Through iterative experiments, the ratio of the pore-forming agent was optimized as 7.5 wt% for the base tile and 10 wt% for the glaze layer under consideration of the balance between mechanical properties and moisture absorption/permeability. Moisture capacity, water absorption and porosity of the prepared glazed tile are 0.469 g/cm³, 25.7 % and 37.7 %, respectively. The compressive breaking strength is more than 600 N (the standard for floor tiles), and the abrasion resistance of the glazed surface reaches Level 2 (meeting the standard for indoor use). Furthermore, the observation in a high-humidity environment reveals that the moisture-permeable glazed tile is capable of controlling condensation on its surface throughout a 24 h-period.

Modeling of a hybrid stirling engine/desalination system using an advanced machine learning approach

In this study, the performance of a hybrid power/freshwater generation system is modeled using a coupled artificial neural network (ANN) model with a pelican algorithm (PA). The proposed system is composed of a Stirling engine fixed to a solar dish, a desalination unit, and a thermoelectric cooler. The Stirling engine is used to generate the electricity required to operate the electrical-powered components of the system as well as to preheat the saline water. The thermoelectric cooler is used to supply the saline water with additional heat as well as to cool the condensation surface of the desalination unit. The performance of the proposed system in terms of water yield, generated power, and system efficiency was considered as the model's output; while the solar irradiance and dish diameter were considered as the model's inputs. In addition to the pelican algorithm, a conventional gradient descent optimizer was employed as an internal optimizer of the ANN model. The prediction accuracy of the two models was compared based on different accuracy measures. The ANN-PA outperformed the conventional ANN model in predicting the water yield, generated power, and system efficiency. The computed root mean square errors of the ANN and ANN-PA models were (1.982 L, 104.863 W, and 1.227 %) and (0.019 L, 1.673 W, and 0.047 %) for water yield, generated power, and system efficiency, respectively.

Research on Metal Corrosion Behaviour of Indirect Air-cooled Circulating Water System

Abstract The indirect air cooling system of an air-cooled power plant consists of a surface condenser and an aluminum radiator. The radiator is usually made of 1050A pure aluminum, and the circulating water pipe connecting the radiator is made of Q235B carbon steel. This article simulates and controls typical water quality parameters such as dissolved oxygen and pH value in indirect air cooling systems using a self-designed simulation device, and studies the influence of various water quality parameters on material corrosion behavior in intercooled circulating water systems when aluminum and carbon steel coexist. The results indicate that factors such as dissolved oxygen, conductivity, pH value, temperature, and redox potential can all affect the corrosion rate of carbon steel and aluminum materials; The increase in temperature and dissolved oxygen leads to an increase in corrosion rate; The main way carbon steel corrodes the system is by consuming dissolved oxygen; The corrosion behaviour in the water circuit will lead to an overall decrease in pH value. In the presence of multiple metals, the influence of iron ions in the solution significantly increases the corrosion rate of aluminum.

The improvement mechanism of styrene grafted nano-Al2O3 on the hydrophobicity of epoxy resin composites: Based on molecular dynamics and experimental research

In the environment with high humidity, water will penetrate into the epoxy resin, resulting in the deterioration of the electrical properties and the decreasing resistance for the heat and corrosion. This study aims to utilize styrene grafted Al2O3 to improve the wettability of the epoxy resin surface and reduce the infiltration of water molecules into the epoxy resin interior. Firstly, the effects of doping PS/Al2O3 on the internal structure of epoxy resin and the diffusion process of water molecules within it are analyzed through the method of molecular dynamics (MD). Subsequently, epoxy resin samples with mass fractions of 1%, 3%, and 5% are prepared, followed by testing for hydrophobicity, water absorption, and the quality of surface condensation under different temperature differentials. The results indicate that the PS/Al2O3 and epoxy resin exhibit a strong interaction, reducing the proportion of free volume fraction of epoxy resin, which lowers the diffusion rate of water molecules. To be specific, the nanoparticles capture water molecules by forming hydrogen bonds with them, limiting the displacement of water molecules and reducing the water absorption of the epoxy resin (maximum reduction of 87%). Moreover, the addition of PS/Al2O3 decreases the adhesion energy of the material surface to water molecules, increasing the static contact angle from 103.58 ° to 125.42 °. Additionally, the total weight of condensation droplets on the material surface is reduced (maximum reduction of 26.02%). These findings serve as a reference for modifying epoxy resin materials in hygrothermal environments.