Pure Evaporation Research Articles

A numerical framework for modeling evaporation and combustion of isolated, spherically-symmetric, multi-component fuel droplets

This paper presents a comprehensive numerical framework for simulating the evaporation and combustion of isolated, spherically-symmetric, multi-component fuel droplets. The framework incorporates a detailed description of chemical reactions in the gaseous phase and is capable of modeling pure evaporation, autoignition, and hot-wire ignition scenarios.The transport equations for mass, species, and energy are solved in both the liquid (droplet) and gaseous (surrounding atmosphere) phases. Diffusion in the liquid phase is described using the Stefan–Maxwell theory, while in the gaseous phase, both molecular and thermal diffusion are considered. The model also includes the thermophoretic effect for carbonaceous particles and accounts for gas radiation through various models, ranging from optically-thin approximations to more complex methods like the P1 and discrete ordinate methods. Non-gray radiative effects are handled using the Weighted-Sum-of-Gray-Gases Model (WSGGM). Liquid/gas interface conditions are evaluated by imposing flux continuity of mass and energy, along with thermodynamic equilibrium for species. Deviations from ideal thermodynamic behavior in the liquid droplet are managed by incorporating a suitable activity coefficient or by using a proper cubic equation of state. Additionally, the presence of supporting fibers is modeled using a simplified one-dimensional approach. The transport equations are solved using the method of lines, with spatial discretization performed via the finite difference method on a body-fitted grid. The resulting system of Differential–Algebraic Equations (DAEs) is then solved using a fully-coupled approach.Thanks to its generality in terms of kinetic and thermodynamic descriptions and the reduced computational time, the proposed framework offers significant potential for advancing our understanding of the complex combustion processes of multi-component liquid fuels and for enhancing the planning and execution of experiments involving isolated fuel droplets.

Localized Evaporative Cooling Explains Observed Ocular Surface-Temperature Patterns.

We determined interblink corneal surface-temperature decline and tear-film evaporation rates of localized tear breakup cold regions (LCRs) and localized tear unbroken warm regions (LWRs) of the corneal surface, as well as that of the overall average corneal surface. Each subject underwent 4 inter-day visits where the interblink corneal surface-temperature history of the right eye was measured using a FLIR A655sc infrared thermographer. Corneal surface temperature history was analyzed to determine the overall, LCR, and LWR temperature-decline rates. Evaporation rates of LCR and LWR regions were determined from the measured LCR and LWR temperature data using the physical model of Dursch et al. Twenty subjects completed the study. Mean (SD) difference of LCR temperature-decline rate was -0.08 (0.07)°C/s faster than LWR (P < 0.0001). Similarly, evaporation rates of LCR and LWR were statistically different (P < 0.0001). At ambient temperature, mean LCR and LWR evaporation rates were 76% and 27% of pure water evaporation flux, respectively. There was no statistically significant difference between the inter-day measured temperature-decline rates and the interblink starting temperature. Significant differences in corneal temperature-decline rate and evaporation rate between LCR and LWR were quantified using infrared thermography. In agreement with literature, LCRs and LWRs correlate directly with fluorescein break-up areas and unbroken tear areas, respectively. Because lipid-evaporation protection is diminished in breakup areas, higher local evaporation rates and faster local cooling rates occur in LCRs relative to LWRs. Our results confirm this phenomenon clinically for the first time.

Spongy polyelectrolyte hydrogel with Janus porous for solar-driven interfacial evaporation and sustainable seawater desalination

Janus-structured hydrogels exhibit excellent advantages in interfacial solar desalination due to their hydrophilicity and low evaporative enthalpy of evaporation, as well as the better salt resistance and mechanical properties. In this research, a simple one-step self-stratification foaming technique is employed to transform hydrogels into Janus structured for seawater desalination. Polyvinyl alcohol (PVA), poly (diallyldimethylammonium chloride) (PDADMAC), and a photothermal material (carbon black, CB) are mechanically stirred with a foaming agent (sodium dodecyl sulfate, SDS), allowing for full mixing and air incorporation, ultimately forming a sponge-like polymeric electrolyte hydrogel with abundant Janus pore structures (PANS-J). The formation of Janus pores in the hydrogel is attributed to the flocculation and high density of hydrophilic PDADMAC, causing it to sink during gelation while hydrophobic PVA floats to the surface. The Janus structure produced by this method reduces heat loss and enhances evaporation performance, achieving a pure water evaporation rate of 3.35 kg m−2 h−1 under sunlight (1 kW m−2). Moreover, quaternary ammonium ions on PDADMAC effectively separate anions and cations in saltwater, reducing salt ion diffusion into the evaporator, preventing premature pore structure blockage, and thus improving long-term evaporator performance which can improve the salt resistance and mechanical properties. By combining these advantages, Janus evaporators hold significant promise for solar-driven water purification and other applications.

"Coir Raincoat"-Boosted Biomimetic Hydrogel for Efficient Solar Desalination and Wastewater Purification.

Solar-driven interfacial evaporation is an efficient method for purifying contaminated or saline water. Nonetheless, the suboptimal design of the structure and composition still necessitates a compromise between evaporation rate and service life. Therefore, achieving efficient production of clean water remains a key challenge. Here, a biomimetic dictyophora hydrogel based on loofah/carbonized sucrose@ZIF-8/polyvinyl alcohol is demonstrated, which can serve as an independent solar evaporator for clean water recovery. This special structural design achieves effective thermal positioning and minimal heat loss, while reducing the actual enthalpy of water evaporation. The evaporator achieves a pure water evaporation rate of 3.88kg m-2 h-1 and a solar-vapor conversion efficiency of 97.16% under 1 sun irradiation. In comparison, the wastewater evaporation rate of the evaporator with ZIF-8 remains at 3.85kg m-2 h-1 for 30 days, which is 16.3% higher than the light irradiation without ZIF-8. Equally important, the evaporator also showcases the capability to cleanse water from diverse sources of contaminants, including those with small molecules, oil, heavy metal ions, and bacteria, greatly improving the lifespan of the evaporator.

Janus structured photothermal conversion materials prepared from carbonized corn straw particles for portable air water extraction devices

The utilization of photothermal conversion materials to enhance the desorption performance of hygroscopic salt solutions through interfacial photothermal effects presents a promising approach for the continuous extraction of water from the atmosphere. To improve the desorption efficiency of hygroscopic salt solutions, the objective of this research is to employ agricultural and forestry residues, such as corn straw, in conjunction with polyurethane sponges, for the production of an innovative Janus structure carbonized biomass photothermal conversion material. Compared to single-layer structured photothermal conversion materials, the pure water evaporation rate increased from 2.42 kg m-2 h-1 to 3.20 kg m-2 h-1 when utilizing the Janus structured photothermal conversion material. Remarkably, this material demonstrates outstanding resistance to salt, allowing it to endure 8 h evaporation cycles with 30 wt% NaCl without salt crystallization. Therefore, it is well-suited for the continuous desorption of liquid hygroscopic agents. Moreover, the portable air–water extraction device, which incorporates Janus structural photothermal conversion material to enhance the performance of 30 % LiCl, has been shown to effectively extract water in practical settings. It achieves a water intake rate of 1.74 L m-2 d-1 at 50 % humidity. This approach is distinguished by its simplicity, cost-effectiveness, and efficient utilization of solar energy resources, providing a promising solution to mitigate the shortage of fresh water resources.

Recent Advances in High-Rate Solar-Driven Interfacial Evaporation.

Recent advances in solar-driven interfacial evaporation (SDIE) have led to high evaporation rates that open promising avenues for practical utilization in freshwater production and industrial application for pollutant and nutrient concentration, and resource recovery. Breakthroughs in overcoming the theoretical limitation of 2D interfacial evaporation have allowed for developing systems with high evaporation rates. This study presents a comprehensive review of various evaporator designs that have achieved pure evaporation rates beyond 4kgm-2h-1, including structural and material designs allowing for rapid evaporation, passive 3D designs, and systems coupled with alternative energy sources of wind and joule heating. The operational mechanisms for each design are outlined together with discussion on the current benefits and areas for improvement. The overarching challenges encountered by SDIE concerning the feasibility of direct integration into contemporary practical settings are assessed, and issues relating to sustaining elevated evaporation rates under diverse environmental conditions are addressed.

Effective solar-driven evaporators with urchin-like CuO particles and directional polyvinylidene fluoride scaffolds via directional dimethyl sulfoxide crystallization and non-solvent induced phase separation

Solar-driven evaporators with vertical channels usually exhibit excellent desalination due to the fast water transportation and excellent salt tolerance, which are often fabricated via a directional liquid nitrogen-assisted ice templating method and freeze-drying process. However, they are reliant on a very limited number of water-soluble polymers and hydrophilic inorganic materials, and the freeze-drying process costs a long time and much energy. A highly efficient and straightforward process for the fabrication of solar-driven evaporators with directional channels from water-insoluble materials is urgent. Here, water-insoluble polyvinylidene fluoride was dissolved in dimethyl sulfoxide (DMSO), and then the solution was engineered to PVDF scaffolds by the combination of directional DMSO crystallization with the commonly porous membrane formation method of non-solvent (water) induced phase separation. The result is the creation of oriented perpendicular pores to the surfaces and framberry-like microparticles on the pore walls. After the in situ deposition of urchin-like CuO particles with high solar adsorption on PVDF scaffolds, PVDF/CuO solar-driven evaporators have been successfully constructed. The evaporate rate depends on the PVDF content and CuO loading. Briefly, PVDF/CuO evaporators fabricated from high PVDF content of more than 3 wt% have low porosity, slow water supply, and poor hydrophilicity, resulting in a low evaporate rate and high evaporation enthalpy. The optimized 3D PVDF/CuO evaporator (V3-9 h) with a PVDF content of 3 wt% and CuO loading of 31.3 ± 1.6 wt% has a high pure water evaporation rate of 3.2 ± 0.2 and 3.5 ± 0.3 kg m-2h−1 under sun illumination at 1 and 2 kW m−2, respectively. And the evaporation enthalpy is as low as 1083.8 ± 25.5 J/g, 55 % lower than pure water. Moreover, the sample exhibits a similar evaporation rate in 3.5 wt% NaCl solution because the verticle channels endow the evaporator with excellent salt tolerance. The facile and scalable fabrication process of solar-driven evaporators with directional channels will greatly boost the development of cost-effective desalination.

Salt-resistant and antibacterial polyvinyl alcohol/chitosan/silver-loaded graphene oxide electrospun nanofiber membrane for high-efficiency solar-driven desalination

To address the issues of low photothermal conversion efficiency, salt deposition and biological contamination in solar-powered desalination, we have developed nanofibrous membranes composed of an optimized ratio of silver-loaded graphene oxide (GO-Ag) composites and polyvinyl alcohol/chitosan (PVA/CS), using a simple and productive electrospinning technique. The synergistic effect of GO and Ag significantly enhanced the photothermal conversion efficiency of the dual-photothermal PVA/CS/GO-Ag-4% electrospun nanofiber membranes (EFMs), which achieved the pure water evaporation rate of 1.67 kg m−2 h−1 and photothermal conversion efficiency of 93.3% under 1 sun (1 kW m−2). Notably, 97% of optical energy is converted to heat when the PVA/CS/GO-Ag-4% EFMs were placed on a homemade evaporation device, achieving up to a simulated seawater evaporation rate of 1.64 kg m−2 h−1 under 1sun, with a desalination rate of 99.99%. More importantly, larger area EFMs are easier to prepare compared to other morphologies of solar evaporators, and larger membranes can be placed on outdoor evaporation units for large-scale effective desalination of seawater used to collect fresh water under natural light. Furthermore, PVA/CS/GO-Ag-4% EFMs exhibited outstanding antibacterial performance against Escherichia coli and Staphylococcus aureus. Considering these strengths, the PVA/CS/GO-Ag-4% EFMs has considerable application potential in solar-driven desalination to solve water crises.

Studies on enhancement of solubility and dissolution properties of rosiglitazone hydrochloride by solid dispersion technique

Rosiglitazone HCl, a member of thiazolidinedione class of antidiabetic agent, improves glycemic control by improving insulin sensitivity. The maximum solubility of rosiglitazone was found at pH 1.2 and solubility decreases up to pH 4.0. At a pH 6.0 and higher pH, solubility reduces drastically. Suitable solid dispersion systems of rosiglitazone with maltodextrin and poloxamer were prepared by solvent evaporation and kneading methods at 1:1 and 1:3 drug: carrier. Drug content, saturation solubility, FTIR, XRD, DSC and In-vitro dissolution were studied. The drug content was uniform, solubility of the drug increased linearly as a function of the carrier concentration and method. The FTIR studies suggest possible interaction at molecular level further justified by XRD and DSC studies. The dissolution study suggests, the increase in drug release was dependent on type of method of preparation. The DP60 and DE60 values were significantly higher (P&lt;0.05) in solid dispersion systems prepared by kneading method when compared to pure rosiglitazone, physical mixture and solvent evaporation method. The dissolution follows first order model and obeyed Hixson- Crowell’s cube root law.

Experimental study on bubbles behaviors in pure water flash evaporation process

Experimental observations were conducted on the phenomenon of flash evaporation. The bubbles appear and grow due to the liquid becomes superheated by a sudden decrease in pressure. During experiments the pure water is flashed at an initial temperature range of 55–90 ℃, an initial liquid film height range of 10–60 mm, and a superheat range of 2–22 K. The spatial and temporal distribution of the bubbles are analyzed during the flashing. And the distribution of bubbles under different superheat and the photo of the behaviors of bubbles were studied. The flashing evaporation can be divided into three stages according to the rate of the bubbles number change and the NEF(non-equilibrium fraction) can express the rate of bubble number at different stages. The number of bubbles is affected by the difference of enthalpy under the same volume of the liquid.

Full-field vapor concentration and temperature field measurement of an evaporating ethanol–water binary sessile drop by tomographic laser absorption spectroscopy

Quantitative measurement of full-field, spatially resolved temperature and concentration field of pure water and ethanol–water binary evaporating drop is realized, in which the gas-phase and interfacial temperature and concentration are accurately captured. By studying the vapor field of evaporating drop under different heating temperatures, it is demonstrated that the method can achieve a spatial resolution below 100 μm and a time resolution of &amp;lt;10 s. Simultaneous gas-phase temperature and concentration field measurements reveal the occurrence of buoyancy convection in the gas phase. Through the analysis of interfacial temperature and concentration distribution, it is observed that in the process of pure water drop evaporation, both buoyancy-driven convection and thermal Marangoni convection exist, while in the ethanol–water binary drop evaporation, the solutal Marangoni flow convection and thermal Marangoni convection are coupled, and the buoyancy convection is suppressed. The interfacial temperature and gas-phase water vapor concentration can be obtained from the water vapor measurement, and combined with the activity coefficient models. The liquid-phase mole fraction of water at the interface and its distribution are also obtained, such that the liquid-phase mole fraction distribution of ethanol at the interface can be obtained, and finally, the concentration of ethanol vapor near the interface is obtained. The full-field, high-resolution measurement of evaporated drops is of substantial significance for in-depth understanding of the evaporation process. The measurement of ethanol–water binary drop evaporation provides a new research perception and method exploiting the spectral dimension, providing both quantitative and qualitative observations for the study of multi-component drop evaporation.

Simultaneous Solar-Thermal Desalination and Catalytic Degradation of Wastewater Containing Both Salt Ions and Organic Contaminants.

Although solar steam generation is promising in generating clean water by desalinating seawater, it is powerless to totally degrade organic contaminants in the seawater. Herein, solar steam generation and catalytic degradation are integrated to generate clean water by simultaneous solar-driven desalination and catalytic degradation of wastewater containing both salt ions and organic contaminants. Stepwise decoration of three-dimensional nickel foam with polypyrrole, reduced graphene oxide (RGO), and cobalt phosphate is realized to obtain polypyrrole/RGO/cobalt phosphate/nickel foam (PGCN) hybrids for solar-driven desalination and catalytic degradation of wastewater containing antibiotics and salt ions. The oxygen-containing groups of the RGO integrated with the porous nickel foam make the porous PGCN hybrid hydrophilic and ensure the upward transport of water to the evaporation surface, and the oxygen vacancies of the cobalt phosphate allow the PGCN to generate abundant highly active singlet oxygen that could still exhibit excellent catalytic degradation performances in the high salinity and highly alkaline environment of seawater. In addition to the high solar light absorbance and satisfactory solar-thermal conversion efficiency of polypyrrole and RGO, the thermally conductive nickel foam skeleton can effectively transfer the heat generated by the solar-thermal energy conversion to the adjacent cobalt phosphate catalyst and nearby wastewater, achieving a solar-thermal-promoted catalytic degradation of organic contaminants. Therefore, a high pure water evaporation rate of 2.08 kg m-2 h-1 under 1 sun irradiation and 100% catalytic degradation of Norfloxacin and dyes are achieved. The PGCN hybrid is highly efficient in purifying seawater containing 10 ppm Norfloxacin and simultaneously achieves a high purification efficiency of 100 kg m-2 h-1.

Biomimetic hydrogel with directional heat regulation for efficient solar desalination

Solar-driven interfacial evaporation desalination has emerged as a promising strategy for alleviating the water scarcity crisis. However, the design of evaporators with excellent heat management and minimal heat loss to achieve high-efficiency clean water production remains a crucial challenge. Herein, inspired by the transpiration of mushrooms in nature, we demonstrated a bionic-structured hydrogel evaporator, fabricated with biomass lotus root starch (LR), polyvinyl alcohol (PVA), and ink-modified carbon quantum dots and TiO2 (i-CQDs-TiO2). The evaporated water can be instantly replenished during evaporation through the internal water circulation of the “stipe”, and the special structural design reduces the transfer of heat to the water. Therefore, the evaporator demonstrates excellent performance, with a pure water evaporation rate of up to 3.78 kg·m−2·h−1 and an efficiency of 98% (1 kW·m−2). More importantly, the evaporator has excellent salt resistance with an average evaporation rate of 3.49 kg·m−2·h−1 in 1–25 wt% brine. In addition, without salt scaling on the evaporation surface in 10 wt% brine for continuous 5 h of illumination. Furthermore, due to the coordinated photocatalysis of i-CQDs and TiO2, the catalytic degradation rates of TB and CR were up to 91.8% and 88.9%, respectively. With an efficient and stable desalination capacity, this solar evaporator with a bionic design offers a new pathway for sustainable solar desalination.

Combustion and Evaporation of Deformable Fuel Droplets

Abstract This study focuses on combustion and evaporation of an isolated freely deforming fuel droplet under convective flow. The droplet shape is modified by varying Weber number at moderate Reynolds numbers. A simplified chemical reaction mechanism is used for combustion modeling. The Direct Numerical Simulation (DNS) results show a net positive effect of Weber number on total evaporation rate (m˙) for both pure evaporation and combustion cases. The enhancement in m˙ for higher Weber number reaches up to 9% for combustion. A nonspherical envelope flame is observed which grows with time. The Damköhler number is higher than 1 for this flame type which leads to faster reaction rates in comparison to evaporation. Hence, the combustion process is seen to be unaffected by droplet shape. An additional comparison between 3-D and 2-D combustion results is performed to understand if 2-D studies can reflect the right physical aspects of this problem. It is found that local evaporation flux in 2-D is 42.5% lower due to lower temperature gradients near the droplet surface for the same inflow velocity. The deformation of droplet is significantly different in 2-D which affects the boundary layer development and the wake flow. This is seen to affect the flame shape at the downstream of droplet. Hence, the 2-D simulations do not recover the correct behaviors.

Fabrication of ATP/PEG/MnO2NWs composite for solar steam generation with high conversion efficiency

Solar steam generation is widely used in seawater desalination because of its high efficiency and environmental protection. However, using low-cost materials to produce efficient solar evaporators is a severe challenge. In this study, a porous carbon material was prepared by combining Attapulgite (ATP), Polyethylene glycol (PEG) and Manganese dioxide nanowires (MnO2NWs) composite, through freeze-drying and high-temperature carbonization. The prepared CAPM aerogel shows a three-dimensional porous structure, which has high evaporation properties in pure water and simulated seawater. Under 1 sun simulated illumination, the pure water evaporation is 1.4574 kg m-2h−1 and the corresponding energy conversion efficiency is 85.94%. The prepared CAPM aerogel showed excellent durability and salt tolerance in 20%Nacl solution, indicating that the CAPM has excellent desalinization performance. In addition, CAPM aerogel has and exhibits super hydrophilic properties, which can transfer water molecules quickly. Due to the advantages of low cost, simple preparation method, and high solar energy conversion efficiency, the CAPM has excellent potential as a photothermal material for solar energy generation.

An Improved Craig–Gordon Isotopic Model: Accounting for Transpiration Effects on the Isotopic Composition of Residual Water during Evapotranspiration

Evapotranspiration (ET) is a crucial process in the terrestrial water cycle, and understanding its stable isotopic evolution is essential for comprehending hydrological processes. The Craig–Gordon (C-G) model is widely used to describe isotopic fractionation during pure evaporation. However, in natural environments, ET involves both transpiration (T) and evaporation (E), and the traditional C-G model does not account for the effect of transpiration on isotopic fractionation. To address this gap, we propose the evapotranspiration-unified C-G (ET-UCG) model, which extends the C-G model by incorporating transpiration’s effect on water isotopes. We verified the validity of the ET-UCG model by comparing its simulation results with the traditional C-G model’s discrete results for a special scenario that simulated the isotopic evolution of residual water after daily transpiration consumption. Further, we simulated two different ET process scenarios using the ET-UCG model to investigate transpiration’s effect on the residual water’s isotopic composition. Our numerical experiments show that transpiration indirectly affects the degree of water isotope fractionation by reducing the true evaporation ratio, even though it does not directly produce isotope fractionation. Therefore, the isotopic composition of residual water estimated by the ET-UCG model is consistently lighter than that estimated using the traditional C-G model in the simulation of ET. Despite different T/ET conditions, the isotopic evolution process follows the same evaporation line. These results highlight the importance of considering transpiration effects when using the C-G model and provide valuable insights into ET processes with potential applications in the field.

Gas-phase transient effects on droplet evaporation and ignition

In order to achieve high efficiency and power density, modern combustors are generally operated at elevated pressures. As the pressure and gas-phase density increase, classical quasi-steady (QS) models of droplet evaporation, ignition, and burning introduce non-negligible errors. In this paper, we extend the QS model to incorporate the gas-phase transient (GT) effect by examining the development of the evaporating boundary layer near the droplet surface. Specifically, the evaporation and ignition of single droplets in an infinite, hot, and oxidizing environment are analyzed. The theoretical result agrees well with the transient numerical simulation for an extensive range of parameters. The proposed theory successfully predicts the GT effect on evaporation lifetime and critical ignition limit of droplets. It is demonstrated that the GT effect increases the droplet evaporation rate while tends to suppress ignition. In comparison with pure evaporation, the ignition of droplets is more severely affected. Additionally, the GT effect increases as the liquid-to-gas density ratio decreases or evaporation intensity increases.

Accurate Measurements and Simulations of the Evaporation and Trajectories of Individual Solution Droplets

A refined numerical model for the evaporation and transport of droplets of binary solutions is introduced. Benchmarking is performed against other models found in the literature and experimental measurements of both electrodynamically trapped and freefalling droplets. The model presented represents the microphysical behavior of solutions droplets in the continuum and transition regimes, accounting for the unique hygroscopic behavior of different solutions, including the Fuchs-Sutugin and Cunningham slip correction factors, and accounting for the Kelvin effect. Simulations of pure water evaporation are experimentally validated for temperatures between 290 K and 298 K and between relative humidity values of approximately 0% and 85%. Measurements and simulations of the spatial trajectories and evaporative behavior of aqueous sodium chloride droplets are compared for relative humidity values between 0 and 40%. Simulations are shown to represent experimental data within experimental uncertainty in initial conditions. Calculations of a time-dependent Péclet number, including the temperature dependence of solute diffusion, are related to morphologies of sodium chloride particles dried at different rates. For sodium chloride solutions, dried particles are composed of collections of reproducibly shaped crystals, with higher evaporation rates resulting in higher numbers of crystals, which are smaller.

Degree of stochastic asymmetry in the tidal tails of star clusters

Context. Tidal tails of star clusters are commonly understood to be populated symmetrically. Recently, the analysis of Gaia data revealed large asymmetries between the leading and trailing tidal tail arms of the four open star clusters Hyades, Praesepe, Coma Berenices, and NGC 752. Aims. As the evaporation of stars from star clusters into the tidal tails is a stochastic process, the degree of stochastic asymmetry is quantified in this work. Methods. For each star cluster, 1000 configurations of test particles were integrated in the combined potential of a Plummer sphere and the Galactic tidal field over the lifetime of the particular star cluster. For each of the four star clusters, the distribution function of the stochastic asymmetry was determined and compared with the observed asymmetry. Results. The probabilities for a stochastic origin of the observed asymmetry of the four star clusters are ≈1.7σ for Praesepe, ≈2.4σ for Coma Berenices, ≈6.7σ for Hyades, and ≈1.6σ for NGC 752. Conclusions. In the case of Praesepe, Coma Berenices, and NGC 752, the observed asymmetry can be interpreted as a stochastic evaporation event. However, for the formation of the asymmetric tidal tails of the Hyades, additional dynamical processes beyond a pure statistical evaporation effect are required.

Adobe bricks as zero-material-cost solar evaporators for water-scarce regions

Consistent access to clean water is amongst the most pressing of global crises, particularly in less developed and off-grid communities. We present a high-efficiency solar evaporation device perfectly suited to address this crisis. Composed solely of soil, the adobe brick is a material that is easy to fabricate, and whose raw constituents are widely available at no cost. Once prepared, these bricks exhibit superb water absorption properties, excellent solar absorption, and efficient photothermal conversion, all of which contribute to a pure water evaporation rate of 2.52 kg m−2 h−1 (77 % evaporation efficiency) and a salt water evaporation rate of 2.16 kg m−2 h−1 under an irradiance of one sun. Suitable pore sizes allow salt water to be converted to fresh water with only minimal salt buildup over 6 h and rapid rejection of particulates to the reservoir below. Variations in soil makeup and inclusion materials are characterized in detail, and evaporation rates are compared. This enables recommendations for the composition of an ideal adobe brick evaporator and important conclusions for the study of solar evaporation materials. While soil composition may be optimized for performance, the high evaporation rates of all samples indicate opportunities for adobe brick desalination across all biomes.