Enhancement Of Evaporation Rate Research Articles

3D structural-engineering evaporator integrating light-space-heat omnibearing regulation

Interfacial solar evaporators designed with sophisticated 3D structure hold the potentiality for ameliorating the evaporation rate through expanding the surface area for evaporation, facilitating water movement and bolstering air convection. However, the most current 3D evaporators are stalemated of constrained light absorption, circumscribed evaporative surface or thermal dissipation which collectively result in the curtailment of evaporation rate escalation. In this work, an omnibearing convergence of new cup-like 3D solar steam generator (C-3D SSG) based on MoS2/C and PVA materials with integrated coordination of light-space-heat is constructed. The innovative cup-like structural design of C-3D SSG successfully embodies the convergence of light, space and heat management through the strategic integration of photothermal materials (PTM), substrate materials and evaporative elements across multiple scales, demonstrating a compelling advancement in light absorption, copious heat diffusion space and prodigious energy-harvesting zone and water evaporation rate enhancement. The omnibearing regulation attains a premium evaporation rate of 3.89 kg m-2 h−1 under 1 Sun illumination with recycle energy of 1.71 W. By incorporating the C-3D SSG for practical application, it can function as an evaporator within a cup, thereby enhancing its practical utility. And C-3D SSG with panoramic convergence provides a broad range of research avenues and methodologies for addressing the water crisis and the development of ISSG technology.

Spatiotemporal variability identification and analysis for non-stationary climatic trends for a tropical river basin of India

The non-stationary behavior of climatic variables has been increasingly recognized as a challenge that disrupts the equilibrium of human-defined climate-based stationary processes, including hydrological and agricultural practices, and irrigation systems. This study aims to investigate long-term trends and non-stationarity in climatic variables across 23 stations of the Krishna River basin, India. Prominent trends in rainfall, temperature, and their extreme indices were identified using the Modified Mann-Kendall (MMK), Bootstrapped Mann-Kendall (BMK), and Sen's Slope Estimator tests, while the Innovative Trend Analysis (ITA) test uncovered hidden trends and potential shifts in climatic patterns. This study addresses a critical research gap by exploring both significant and hidden trends in climatic variables, providing a better understanding of future dynamics. Traditional methods like MMK and Sen's Slope were insufficient to reveal these hidden trends, but ITA offered a more comprehensive analysis. The findings revealed an increase in total annual rainfall for almost 50% of the basin, which aligns with rising maximum temperatures, suggesting enhanced evaporation rates and subsequent fluctuations in rainfall patterns. Seasonal analysis indicated a shift towards decreased rainfall during winter and pre-monsoon seasons, contrasted by increased precipitation during the monsoon and post-monsoon periods, highlighting a clear alteration in rainfall distribution. The Simple Daily Intensity Index (SDII) and other indices suggest intensified rainfall events despite a decrease in the number of rainy days, indicating fewer but more intense events. Temperature analysis showed an overall increase in maximum temperatures, with the Diurnal Temperature Range (DTR) significantly increasing across all stations, implying greater daily temperature variations and potential for intensified water cycles and extreme climatic events. Furthermore, the study simplifies these trends by classifying them into two attributes: intensity and frequency, aiding policymakers in site-specific management of water resources and planning for future climatic scenarios. The presence of non-stationarity in extreme rainfall was confirmed by the Augmented Dickey-Fuller (ADF), Phillips-Perron (PP), and Kwiatkowski-Phillips-Schmidt-Shin (KPSS) tests. These findings are significant as they conclude how climate change is altering hydrological patterns at each station. The study emphasizes the necessity for adaptive management strategies to mitigate the adverse impacts on agriculture, infrastructure, and human safety.

Enhancing Solar Steam Generation of Hydrogels via Silver Nanoparticle-Doped Cellulose Nanofibers.

Solar steam generation (SSG) is regarded as an efficient approach for harnessing solar energy to purify polluted or saline water. Herein, we demonstrate a hydrogel composed of cellulose nanofibers (CNFs), polyethylenimine (PEI), and reduced graphene oxide (rGO) that functions as an independent solar steam generator, which shows enhanced solar water evaporation efficiency by incorporating silver nanoparticles (AgNPs). It presented that the presence of AgNPs increases the photothermal conversion efficiency and thermal conductivity of the evaporator and reduces the enthalpy of evaporation. As a result, an outstanding water evaporation rate of 3.62 kg m-2 h-1 and a photothermal conversion efficiency of 96.25% are successfully obtained under one sun illumination. Also, the resulting hydrogel exhibits exceptional mechanical properties, as well as outstanding desalination and salt-resistant abilities during prolonged seawater desalination. In oil/water mixtures, the evaporation of the hydrogel decreases to 2.94 kg m-2 h-1, owing to the oil layer barrier. This work paves a reference approach to produce easily addressed cellulose nanofiber (CNF)-based hydrogel evaporators with significantly enhanced evaporation rates.

Halfa grass assembled double-layered hydrogel evaporator for sunlight-driven steam generation and selective uranium extraction

Fresh drinking water and energy are crucial for the human society to live in a sustainable way, and both of these could be attained from the seawater. Herein, we designed a double-layered hydrogel evaporator (PCG@FCG) by using calcined carbon fiber derived from halfa grass (Desmostachya bipinnata) as a light absorbing photothermal material. The bottom hydrophilic layer composed of chitosan (CS), carboxy methyl cellulose (CMC), and amidoxime-modified chitosan (AOC), which helps in water transport to the upper surface of evaporator. The amidoxime modified chitosan helps in selective binding and recovery of uranium from the seawater. Such a judiciously designed PCG@FCG evaporator shows light absorbance of 96 %, stable evaporation rate of 2.0 kg m−2 h−1, having an outstanding selective uranium recovery of 325 mg g−1 under one sun irradiation. These outcomes result from the inherent structural porosity, enhanced evaporation rate, and selectively designed uranium binding sites. In addition, excellent salt-mitigating ability to promote uninterrupted evaporation, ability to purify the organic-contaminated wastewater/seawater endow the PCG@FCG evaporator with efficient seawater desalination ability and selective adsorption of uranium from the seawater. Overall, this innovatively-designed floating evaporator offers a sustainable approach to utilize the lavish resources in the seawater.

Enhanced solar-driven evaporation and mineral extraction from hypersaline produced water using low-cost microporous photothermal foam

The beneficial reuse of produced water (PW) holds significant promise to alleviate water scarcity. However, it still suffers major limitations associated with the high cost of treatment due to energy consumption, economics of scale, and the complex physiochemical constituents. PW is a hypersaline (TDS ∼ 250,000 mg/l) oilfield water with bio-species, organic matter, anions, divalent cations, and radioactive elements. A sustainable treatment option is solar-driven floating photothermal evaporation (PTE), a desalination technology implemented for seawater characterized by simpler chemical compositions and low salinity.In this work, the photothermal evaporator for PW was fabricated using low-cost commercially available charcoal polyurethane foam. The engineered macrochannels and structural alterations created unique pathways for salt extraction and evaporation; and ensured hydrodynamic balance between the rates of capillary flow and evaporation. This novel design mitigated flooding or dry out on the evaporating surface and kept the system running steadily while simultaneously harvesting freshwater and valuable salts.The key findings from this work are (a) the development of a novel temperature ratio-based method to determine optimum PTE thickness that results in maximum evaporation and thermal localization, (b) the development of the empirical correlation between the rate of thermal localization, evaporation rate, and PTE thickness. It combines the interplay of convection, evaporative flux, conduction, heat capacitance, and thickness on the thermal response of PTE foam to incident solar flux, and (c) experimental evidence revealing efflorescence and subflorescence salt on the evaporating surface and pore, and (d) enhanced evaporation rate of 118 % or 71.6 kg/day-m2 of clean water from chemically complex hypersaline produced water. These findings are significant for the engineering design and estimation of the performance of a PTE in a solar-driven evaporation system.

Boosting solar vapor generation and desalination by low-cost reduced graphene oxide/cellulose aerogel and multiple energy utilization

Solar interfacial vapor generation provides one of promising pathways for seawater desalination and wastewater treatment with minimized carbon footprint. There are still great challenges in architecting low-cost solar evaporators for rapid water transfer channels and high-throughput evaporation rate. Herein, an aerogel with reduced graphene oxide and cellulose nanofibers (rGC) was fabricated by one step self-assembly method. The rGC possessed excellent light absorption, superhydrophilic ability, and reduced energy requirement of water evaporation. The evaporation rate of rGC-3 (height of 3 cm) achieved 3.19 kg m−2 h−1 with the evaporation efficiency of 114.3% under 1 sun irradiation. The suspended vapor was timely diffused by directional convection, so as to minimize the stagnation of vapor in openly channels and continuously harvest additional environmental energy. The water evaporation behavior was improved to 9.40 kg m−2 h−1 under a convective flow of 2.5 m s−1, well beyond 200.3% of non-convective condition. Additionally, the three-dimensional rGC-3 consistently evaporated in 3.5 wt% brine and the evaporation rate kept at 8.61 - 9.39 kg m−2 h−1. In the outdoor solar water desalination, rGC-3 had excellent desalination behavior and evaporative performance in weak sunlight and relative low temperature. The realization of enhanced evaporation rate, overall seawater purification capability, and high cost-effectiveness of the nanofiber aerogel provide a new inspiration for designing high-throughput solar interfacial evaporator.

Liquid-Liquid Phase Separation Induced by Vapor Transfer in Evaporative Binary Sessile Droplets.

Drying of binary sessile droplets consisting of ethanol and octamethyltrisiloxane on a high-energy surface is investigated. During the process of evaporation, the droplets undergo liquid-liquid phase separation, resulting in the appearance of microdroplets at the liquid-air interface, which subsequently violently burst. This phase separation is attributed to water vapor transfer into the droplet, which modifies the solubility and leads to the formation of a ternary mixture. The newly formed ternary mixture may undergo nucleation and growth or spinodal decomposition, depending on the droplet composition path. By control of the relative humidity of air, phase separation can be mitigated or even eliminated. The droplets also display high mobility and complex wetting behavior due to phase separation, with two contracting and two spreading stages. The mass loss experiments reveal that the droplets undergo three distinct drying stages with an enhanced evaporation rate observed during the phase separation stage. A modified diffusion-limited model was employed to predict the evaporation rate, accounting for the physiochemical changes during evaporation and proved to be consistent with experimental observations. The findings of this work enhance our understanding of a coupled fundamental process involving the evaporation of multicomponent mixtures, wetting, and phase separation.

Photothermal Janus fabrics enabling persistent directional sweat-wicking in personal wet-thermal management

Directional sweat-wicking by Janus fabrics has gained substantial attention in promoting personal wet-thermal management for optimal human comfort. During intense physical exercise, excessive sweating can cause the flooding of fabrics and weaken their wicking capabilities once the inner capillary channels are saturated. To address this issue, we develop a photothermal Janus fabric through a facile polydopamine (PDA) deposition followed by single-sided spray-coating of hydrophobic polydimethylsiloxane (PDMS). Such innovative fabrics enable directional sweat-wicking through a Janus structure and persistent removal of excessive sweat by solar-powered evaporation. Under sunlight, our photothermal Janus fabrics exhibit an enhanced evaporation rate, approximately twice compared with that of conventional Janus fabrics (∼1.143 ± 0.027 kg m-2h−1), making them suitable for high sweating rates during vigorous exercise. Furthermore, these fabrics help to maintain the skin temperature within the normal range, preventing hypothermia caused by profuse sweating. In addition, our photothermal Janus fabrics exhibit excellent washing durability even after multiple washing cycles, ensuring prolonged performance and safety.

Molecular dynamics simulation of argon pool boiling: A comparative study of employing nanoparticles and creating tree-root type nanostructures

This paper is aimed to investigate the effectiveness of innovative nanostructured surfaces in terms of heat transfer and evaporation rate enhancement during the pool boiling process of argon atoms by employing molecular dynamics simulation. LAMMPS software and Lennard-Jones potential are used for the simulation and determination of the force field. The fundamental thought of creating these novel geometries (tree-root type nanostructures) is to use the branches as a barrier against liquid cluster separation, which leads to fluid temperature enhancement. First, the framework of simulation is validated, and then the results of creating two types of copper tree-root nanostructures are presented and compared with three cases which include: adding platinum, aluminum, and copper nanoparticles to the argon fluid on the plain copper substrate. The results revealed that creating tree-root type nanostructures postponed the separation of the liquid cluster in comparison with adding nanoparticles. In addition, the tree-root type nanostructures can enhance the evaporation rate and the argon temperature up to 60.05% and 17.13% more than adding nanoparticles, respectively. On the other hand, these nanostructures improve the maximum heat flux and corresponding convective heat transfer coefficient by 15.46% and 26.86% compared to the cases of adding nanoparticles, respectively.

3D Graphene Composite Foams for Efficient and Stable Solar Desalination of High‐Salinity Brine

Solar‐driven interfacial evaporation (SIE) is a promising desalination technology that utilizes solar energy and seawater. However, most SIE systems are limited by high cost, complex fabrication, and low salt tolerance. Herein, a simple method is presented for preparing a 3D graphene/carbon nanotubes/polypyrrole foam (GCPF) evaporator that exhibits high evaporation efficiency, excellent mechanical performance, and stable solar desalination of high‐salinity brine. The excellent processability of melamine foam enables the easy preparation of the 3D GCPF, which exhibits an enhanced evaporation rate of 4.012 kg m−2 h−1 and a photothermal conversion efficiency of 97.8% under one sun irradiation. Compared with the 2D sample, the GCPF‐3 evaporator utilizes solar energy more efficiently and maintains higher evaporation performance even when the light angle changes. Moreover, the 3D GCPF shows remarkable salt tolerance and durability, achieving a stable evaporation rate of 4.005 kg m−2 h−1 for 30 h with a salinity of 25 wt%, which is the best‐reported result among solar desalination systems. This work provides new insights into the design of 3D graphene composite foams and demonstrates their potential applications in continuous solar desalination.

Enhancement of evaporation rate in subcooled nucleate pool boiling with suspended hydrophilic particles

Enhancement of evaporation rate in subcooled nucleate pool boiling with suspended hydrophilic particles

Biomass-Printed Hybrid Solar Evaporator Derived from Bio-polluted Invasive Species, a Potential Step toward Carbon Neutrality.

Biomass-based photothermal conversion is of great importance for solar energy utilization toward carbon neutrality. Herein, a hybrid solar evaporator is innovatively designed via UV-induced printing of pyrolyzed Kudzu biochar on hydrophilic cotton fabric (KB@CF) to integrate all parameters in a single evaporator, such as solar evaporation, salt collection, waste heat recovery for thermoelectricity, sieving oil emulsions, and water disinfection from microorganisms. The UV-induced printed fabric demonstrates stronger material adhesion as compared to the conventional dip-dry technique. The hybrid solar evaporator gives an enhanced evaporation rate (2.32 kg/m2 h), and the complementary waste heat recovery system generates maximum open-circuit voltage (Vout ∼ 143.9 mV) and solar to vapor conversion efficiency (92%), excluding heat losses under one sun illumination. More importantly, 99.98% of photothermal-induced bacterial killing efficiency was achieved within 20 min under 1 kW m-2 using the hyperthermia effect of Kudzu biochar. Furthermore, numerical heat-transfer simulations were performed successfully to analyze the enhanced interfacial heat accumulation (75.3 °C) and heat flux distribution of the thermoelectric generators under one sun. We firmly believe that the safe use of bio-polluted invasive species in hybrid solar-driven evaporation systems eases the environmental pressure toward carbon neutrality.

Rocket drops: The self-propulsion of supercooled freezing drops

Supercooled water drops move spontaneously while freezing in vacuum. This self-propulsion phenomenon is caused by an enhanced evaporation rate from the frozen regions of the drops. The evaporating molecules carry momentum, and the drops acquire an opposite momentum, the same as in rocket propulsion.

Evaporative and Wicking Functionalities at Hot Airflows of Laser Nano-/Microstructured Ti-6Al-4V Material.

A novel multifunctional material with efficient wicking and evaporative functionalities was fabricated using hierarchical surface nano-/microstructuring by femtosecond laser micromachining. The created material exhibits excellent multifunctional performance. Our experiments in a wind tunnel demonstrate its good wicking and evaporative functionalities under the conditions of high-temperature airflows. An important finding of this work is the significantly enhanced evaporation rate of the created material compared with the free water surface. The obtained results provide a platform for the practical implementation of Maisotsenko-cycle cooling technologies for substantially increasing efficiency in power generation, thermal management, and other evaporation-based technologies. The developed multifunctional material demonstrates long-lasting wicking and evaporative functionalities that are resistant to degradation under high-temperature airflows, indicating its suitability for practical applications.

Counter-Intuitive Evaporation in Nanofluids Droplets due to Stick-Slip Nature.

We experimentally investigate the evaporation characteristics of a sessile ethanol droplet containing Al2O3 and Cu nanoparticles of sizes 25 and 75 nm on a heated substrate using shadowgraphy and infrared imaging techniques. Our results demonstrate that the droplet contact line dynamics resulting from the presence of various nanoparticles plays a dominant role in the evaporation process. This is in contrast to the widely held assumption that the enhanced evaporation rate observed in sessile nanofluid droplets is due to the higher thermal conductivity of the added nanoparticles. We observe that even though the thermal conductivity of Al2O3 is an order of magnitude lower than that of Cu, droplets containing 25-nm-sized Al2O3 exhibit pinned contact line dynamics and evaporate much more rapidly than droplets containing Cu nanoparticles of both sizes and 75 nm Al2O3 nanoparticles that exhibit stick-slip behavior. We also found that the droplets with different nanoparticles display distinct thermal patterns due to the difference in contact line behavior, which alters the heat transfer inside the droplets. We establish this counter-intuitive observation by analyzing the temporal variations of the perimeter, free surface area, and deposition patterns on the substrate.

One-step synthesis of Enteromorpha graphene aerogel modified by hydrophilic polyethylene glycol achieving high evaporation efficiency and pollutant tolerance

Photothermal evaporation using solar energy is a sustainable way to produce fresh water from seawater. Aiming to explore functional materials as a solar-energized evaporator with enhanced evaporation rate and pollutant tolerance, this study was to synthesize a self-floating composite graphene aerogel (GA) doped with Enteromorpha and modified polyethylene glycol (PEG), named as PEGA using solar energy for desalination. Physio-chemical properties and evaporative mechanism of PEGA were experimentally investigated and analyzed with respect to molecular weight, PEG dosage, and ratio of Enteromorpha and graphene oxide. Experimental data revealed that the modification of PEG improved hydrophilic functional ability of PEGA, resulting in increasing the evaporation rate and photothermal conversion efficiency up to 2.55 kg/(m2·h) and 105.71 %, respectively. The ion removal rate of seawater exceeds 99.99 % via the PEGA conducted solar evaporation. Furthermore, PEGA possessed an excellent property of salinity emulsion pollution tolerance. Particularly, the evaporation rate of the PEG-modified biomass-based aerogel was 2.84 kg/(m2·h) in a 15 wt% NaCl solution (1 sun, 6 h) and 2.50 kg/(m2·h) at 1 h. The formation of hydrogen bonds between –OH of PEG and water molecules assist to conduct water along the graphene matrix to improve water evaporation. The cost of the graphene aerogel modified by Enteromorpha was reduced by 38.88 % less than the original graphene aerogel. The results from this study will greatly promote the application of graphene aerogel for desalination via solar evaporation.

Biomass‐Inspired Solar Evaporator for Simultaneous Steam and Power Generation Enhanced by Thermal‐Electric Effect

Solar‐driven interfacial evaporation systems have been considered to achieve broad application prospects in the field of cogeneration of steam and electricity. However, the electricity generated is often independent of the photothermal system, hindering their integration. Compared with traditional materials such as metals and semiconductors, the application of biomass materials can solve the problems of high cost and environmental pollution in the expansion and relevance of interfacial evaporation technology. Herein, the solar evaporator composed of carbonized sphagnum palustre with cellulose fabric (CSPF) is fabricated for simultaneous steam production and power generation. Additionally, a device consisting of the CSPF and other accessories such as heating wires is designed to enhance steam production by self‐driven electrothermal heating. The self‐driven solar evaporator endows enhanced evaporation rates to 2.12 kg m−2 h−1 under electrothermal effect and the high electrical energy outputs of 520 mV. The solar evaporator has good salt tolerance and excellent cycle stability, maintaining a high evaporation rate in high‐salt solutions and after 24 cycles of testing. The outdoor evaporation tests reveal the encouraging performance of the steam and energy generators in real environment. Such superior performance of comprehensive device has great potential for integrated and sustainable application in cogeneration systems.

An Enhanced Evaporation Rate Water-Cycle Algorithm for Global Optimization

Water-cycle algorithm based on evaporation rate (ErWCA) is a powerful enhanced version of the water-cycle algorithm (WCA) metaheuristics algorithm. ErWCA, like other algorithms, may still fall in the sub-optimal region and have a slow convergence, especially in high-dimensional tasks problems. This paper suggests an enhanced ErWCA (EErWCA) version, which embeds local escaping operator (LEO) as an internal operator in the updating process. ErWCA also uses a control-randomization operator. To verify this version, a comparison between EErWCA and other algorithms, namely, classical ErWCA, water cycle algorithm (WCA), butterfly optimization algorithm (BOA), bird swarm algorithm (BSA), crow search algorithm (CSA), grasshopper optimization algorithm (GOA), Harris Hawks Optimization (HHO), whale optimization algorithm (WOA), dandelion optimizer (DO) and fire hawks optimization (FHO) using IEEE CEC 2017, was performed. The experimental and analytical results show the adequate performance of the proposed algorithm.

Bio-inspired salt-fouling resistant graphene evaporators for solar desalination of hypersaline brines

Solar seawater desalination may provide an economical and environmentally friendly means to address the global freshwater crisis. However, salt crystals can precipitate and accumulate on evaporator surfaces during solar seawater desalination, leading to significant deterioration of the performance. Current anti-salt fouling strategies generally suffer from low evaporation rates particularly during the desalination of hypersaline brines. In this paper, we propose bio-inspired graphene evaporators with well-aligned tubular channels to achieve effective solar desalination of hypersaline brines with simultaneously enhanced evaporation rate and long-term anti-salt fouling performance. The unique hierarchical large and small channels inside the evaporators not only increase evaporating surface area, but also provide low-tortuosity pathways for fast salt ion diffusion from the evaporation surfaces to bulk brine. Consequently, the proposed device achieves a high evaporation rate of 2.60 kg m−2 h−1 during a 24-h continuous evaporation test in a hypersaline brine (20 wt% NaCl solution) under one-sun irradiation, among the best values reported in previous studies. Meanwhile, salt precipitation is observed to preferentially occur at the edges of the top surface, leaving the main evaporation area clean during the desalination process. The bio-inspired graphene evaporators with well-aligned tubular channels exhibit great potential for practical solar seawater desalination applications.

Evaporation and liquid-phase separation of ethanol–cyclohexane binary drops under acoustic levitation

Evaporation of cyclohexane and ethanol binary drops under acoustic levitation was investigated. The aim was to understand the effect of acoustic levitation on the evaporation dynamics and involved physical processes of the binary drops. We report the occurrence of liquid-phase separation of the binary drop during evaporation under acoustic levitation. Through systematic experiments, it was found that the enhanced evaporation rate of the drop under acoustic levitation led to a significant temperature decrease. In addition, driven by external acoustic streaming, water vapor tended to be enriched and condensed on the drop surface. Because ethanol is extremely soluble in water, tiny cyclohexane droplets were extracted from ethanol owing to water condensation. In addition, driven by the internal flow of the acoustically levitated drop, the extracted cyclohexane droplets coalesced, eventually resulting in macro-segregation in the drop. These findings provide new insights into the evaporation dynamics of acoustically levitated drops, thus, shedding light on industrial purification and separation of volatile liquids with opposite water solubilities, such as cyclohexane and ethanol.