Water Collection Efficiency Research Articles

A Pragmatic Device Based on a Double-Sided Functional Structure for Efficient Water Harvesting.

Water collection from fog has received much attention to meet the challenges of scarcity of clean drinking water in desert and arid regions. Currently, solar‐thermal technology is being used as an efficient, sustainable, and low‐cost method for water desalination to produce clean water. To collect the clean water, in recent years, most researchers have designed the structure of water collection surfaces. However, the heat released during the liquefaction process of droplets has an adverse effect on the condensation of droplets, and thus affecting the water collection efficiency. Here, in order to improve water collection efficiency, a radiative cooling layer is introduced on the back of the collection surface to dissipate the heat released during droplet liquefaction. The radiative cooling layer, consisting of poly(vinylidene fluoride‐co‐hexafluoropropene) embedded with SiO2 and CaMoO4 nanoparticles, can theoretically cool 18.1 °C below the ambient temperature in the daytime. With the addition of cooling coating on the back of the water collection surface, the water harvesting efficiency can be increased by 43–52%. The developed water harvesting device may provide a new pathway to the efficient collection of fresh water.

Optimal Design of Multilayer Fog Collectors.

The growing concerns over desertification have spurred research into technologies aimed at acquiring water from nontraditional sources such as dew, fog, and water vapor. Some of the most promising developments have focused on improving designs to collect water from fog. However, the absence of a shared framework to predict, measure, and compare the water collection efficiencies of new prototypes is becoming a major obstacle to progress in the field. We address this problem by providing a general theory to design efficient fog collectors as well as a concrete experimental protocol to furnish our theory with all the necessary parameters to quantify the effective water collection efficiency. We show in particular that multilayer collectors are required for high fog collection efficiency and that all efficient designs are found within a narrow range of mesh porosity. We support our conclusions with measurements on simple multilayer harp collectors.

A fog-collecting surface mimicking the Namib beetle: its water collection efficiency and influencing factors.

Shortage of water resources and deterioration of water quality are becoming more and more serious today. Inspired by Namib Desert beetles, scientists designed biomimetic fog collection materials to obtain fresh water. The overview of this field is limited and mainly concerned with the preparation and application. In this paper, we focused on the water collection efficiency of surfaces inspired by beetles and discussed their influence on the water collection efficiency from three aspects: surface wettability, surface structure and surface pattern distribution.

Mechanically durable and long-term repairable flexible lubricant-infused monomer for enhancing water collection efficiency by manipulating droplet coalescence and sliding

Lubricant-infused surfaces have attracted widespread attention due to their excellent liquid and organic solution repellency. On account of their high condensation heat transfer coefficient and low nucleation energy barrier, many lubricant-infused surfaces have been applied in water collection. However, they have a number of shortcomings, such as an unstable lubricating layer, poor mechanical/chemical stability and hard shedding, which severely limit the application of slippery surfaces. In this work, the silicone oil was infused into a superhydrophobic monomer (SHM) to form a flexible lubricant-infused monomer (FLIM) with outstanding sliding ability and omniphobicity for low surface energy liquids. Because the silicone oil is similar to the base molecule, there is a strong interacting force to hold the lubricant layer to the surface of the SHM. In addition, the high viscosity of the silicone oil further strengthens the lubricant layer adhesion. Therefore, the FLIM could resist hot liquid and high shear stress (up to 5000 rpm). In addition, the FLIM substrate possessed a self-similar low surface energy structure, which could endure various physical and chemical damages, such as abrasion, scratching, stretching, strong acid and alkali. Finally, pinned droplets could coalesce into large droplets to slide down its surface, resulting from the strain/release due to the high degree of deformation of the surface, which highly enhanced water/liquid coalescence and collection. The preparation of the FLIM was green and the chemicals involved were inexpensive and environmentally friendly, and thus it can be applied for large-scale water collection.

Textured materials with extreme wettability for water harvesting from aerosols

The creation of methods for complete and cost-effective collection of water droplets from an aerosol which arises as a by-product of the low-potential heat uptake from industrial devices, is one of the key tasks of rational use of water resources contributing to the improvement of the environment near large industrial enterprises. This paper shows how the application of materials with extreme wettability and a specific surface topography in spray separators can significantly increase the efficiency of water collection.

Extreme-Wettability Textured Materials for Water Collection from Aerosols

Creation of methods for complete and cost-effective collection of water droplets from an aerosols arising as a by-product of the low-potential heat uptake from industrial equipment is one of the key tasks of rational use of water resources contributing to the improvement of the environment near large industrial enterprises. This paper shows how the application of materials with extreme wettability and a specific surface topography in spray separators can significantly increase the water collection efficiency.

Multibioinspired slippery surfaces with wettable bump arrays for droplets pumping

Droplet manipulation is playing an important role in various fields, including scientific research, industrial production, and daily life. Here, inspired by the microstructures and functions of Namib desert beetles, Nepenthes pitcher plants, and emergent aquatic plants, we present a multibioinspired slippery surface for droplet manipulation by employing combined strategies of bottom-up colloidal self-assembly, top-down photolithography, and microstructured mold replication. The resultant multilayered hierarchical wettability surface consists of hollow hydrogel bump arrays and a lubricant-infused inverse opal film as the substrate. Based on capillary force, together with slippery properties of the substrate and wettability of the bump arrays, water droplets from all directions can be attracted to the bumps and be collected through hollow channels to a reservoir. Independent of extra energy input, droplet condensation, or coalescence, these surfaces have shown ideal droplet pumping and water collection efficiency. In particular, these slippery surfaces also exhibit remarkable features including versatility, generalization, and recyclability in practical use such as small droplet collection, which make them promising candidates for a wide range of applications.

Durable Lubricant-Impregnated Surfaces for Water Collection under Extremely Severe Working Conditions.

It is worth noting that the multifunctional surfaces are highly desirable for water collection applications on droplet nucleation and removal. Although the superhydrophobic surfaces is beneficial to water collection due to easily shed liquid drops and favorable heat-transfer performance, the pinned condensed water droplets within the rough structure and a high thermodynamic energy barrier for nucleation severely limit the water collection efficiency. Recently, the liquid-infused surfaces have been significant for condensation heat transfer and droplet nucleation but have poor durability. In this work, under the UV light, polydimethylsiloxane was grafted onto ZnO nanorods (through Zn-O-Si bond), and the residual unbonded silicone oil was used as the lubricant, so that it form a hierarchical lubricant-impregnated surfaces. Because of high viscosity of silicone oil and strong intermolecular force between silicone oil and PDMS brush, the lubricant can be firmly fixed in micronanostructure to form a durable lubricant layer. For example, the LISs have outstanding properties such as boiling water repellency, omniphobicity of various liquid, and hot water resistance. Under a self-made hot vapor collection device, the surface can maintain good water collection capacity and there is no obvious change in the lubrication layer. After exposing in sunlight for 7 days and subjecting them to 25 times heating/cooling cycles (heating at 150 °C), the LISs exhibit excellent water collection and repairability. After measurement, the oil content in the water is 43 mg/L, which is harmless to the human body. Through the high-water collection efficiency and durable lubricant layer, the LISs can be applied on a large scale in the water collection industry.

Water Harvesting of Bioinspired Microfibers with Rough Spindle-Knots from Microfluidics.

Heterostructure rough spindle-knot microfibers (HRSFs) are fabricated via a flexible parallel-nozzle microfluidic method. In this method, the bioinspired HRSF with a roughness gradient between spindle-knots and joints, can be manufactured in large-scale, and with which the size of the spindle-knots and joints can be precisely adjusted by regulating flow rates. The HRSFs, fabricated with chitosan and calcium alginate, have strong mechanical properties and corrosion resistance in acid environment (pH = 5) and alkaline environment (pH = 9), respectively. More attractively, under controlled treatment conditions, the morphology of the spindle-knots on the HRSFs can be effectively managed by changing the composite content of calcium chloride in the fluid. During the water collection process, tiny droplets of moisture can be captured on the surface of the HRSFs, subsequently, the droplets can coalesce and be transported from joint to spindle-knot sections. It is demonstrated that the surface morphology of spindle-knots directly influences the water collection efficiency, where a higher roughness gradient generates higher water collection efficiency. This parallel-nozzle microfluidic technology provides a low-cost and flexible method to manufacture high biocompatibility bioinspired rough spindle-knot microfibers, which has many potential applications in large-scale water collection, sustained drug release, and directional water collection.

Assessing the Influence of Microphysical and Environmental Parameter Perturbations on Orographic Precipitation

AbstractMicrophysical (MP) schemes contain parameters whose values can impact the amount and location of forecasted precipitation, and sensitivity is typically explored by perturbing one parameter at a time while holding the rest constant. Although much can be learned from these “one-at-a-time” studies, the results are limited as these methods do not allow for nonlinear interactions of multiple perturbed parameters. This study applies the Morris one-at-a-time (MOAT) method, a robust statistical tool allowing for simultaneous perturbation of numerous parameters, to explore orographic precipitation sensitivity to changes in microphysical and environmental parameters within an environment characteristic of an atmospheric river. Results show parameters associated with snow fall speed coefficient As and density ρs, ice-cloud water collection efficiency (ECI), rain accretion (WRA), relative humidity, zonal wind speed, and surface potential temperature cause the largest influence on simulated precipitation. MP and environmental parameter perturbations can cause precipitation changes of similar magnitude, but results vary by location on the mountain. Different environments are also tested, with As being the most influential MP parameter regardless of environment. Fewer MP parameters influence precipitation in a faster-wind-speed environment, possibly due to the stronger dynamical forcing upwind and different wave dynamics downwind, compared to a slower-wind-speed environment. Finally, perturbing MP parameters within a single scheme can result in precipitation variations of similar magnitude compared to using entirely different microphysics schemes. MOAT results presented in this study have implications for Bayesian parameter estimation methods and stochastic parameterization within ensemble forecasting.

Experimental Study on the Wet Electrostatic Precipitator for Purifying Converter Gas

Converter gas must be purified by the wet electrostatic precipitator for the combined cycle power plant because of its high dust concentration. However, most of the electrostatic precipitator is placed after the gas tank in order to operate safely. This will result in larger amounts of dust entering into the gas tank or the atmosphere. It causes the gas tank’s seal damaged and air pollution. Based on the above reasons, the authors put forward a new process which places the wet electrostatic precipitator before the gas tank for purifying the converter gas, and analyzed the feasibility of this process. The research on corona discharge of converter gas in electrostatic precipitator, V-I characteristics affected by the water pressure and collection efficiency of the dust particles was carried out at an experimental system. The results show that corona discharge performance of converter gas was good and the V-I characteristic curve gradually moves down when the gas pressure increases. Spraying water can promote the collection efficiency of the dust particles. When the water pressure is 0.3MPa, the collection efficiency is 97.4%. The optimal water pressure in wet electrostatic is 0.3~0.5 MPa. From the results and analysis, it is feasible to purify converter gas by using the wet ESP which is placed before the gas tank.

Constructing hierarchically hydrophilic/superhydrophobic ZIF-8 pattern on soy protein towards a biomimetic efficient water harvesting material

Inspired by the Stenocara beetle that can collect water from moist air in the Namib desert, here, we propose a simple dynamic control of crystal growth of ZIF on a natural polymer, soy protein. By adjusting the precursor concentration as well as the crystal growth time, hierarchical micro-/nano-crystals are constructed on the protein film surface. Taking advantage of the size difference of such crystals, selectively hydrophobic modification with a low surface-energy agent, stearic acid, can be performed on the surface, creating controllably hydrophilic/superhydrophobic patterns in favor of efficient water harvesting from fog. The effects of the as-prepared patterns on the water condensation behavior and collection efficiency are investigated; the maximum water collection efficiency, notably, can reach as high as 917.6 mg·cm−2·h−1. The results suggest that the biomimetic films hold a potential application in atmospheric water collection and the simple pattern-constructing approach is helpful to develop functional surface-patterned materials.

Bioinspired Hierarchical Surfaces Fabricated by Femtosecond Laser and Hydrothermal Method for Water Harvesting.

The world is facing a global issue of water scarcity where two-thirds of the population does not have access to safe drinking water. Water harvesting from the ambient environment has a potential equivalent to ∼10% of the fresh water available on the earth's surface, but its efficiency requires a special control of surface morphology. We report a novel facile physicochemical hybrid method that combines femtosecond laser structuring with hydrothermal treatment to create a surface with a well-arranged hierarchical nanoneedle structures. Polydimethylsiloxane treatment of the thus-produced hierarchical structures nurtured superhydrophobic functionality with a very low water sliding angle (∼3°) and a high water adhesion ability. About 2.2 times higher water-collection efficiency was achieved using hierarchical structures over untreated flat Ti surfaces of the same area under a given experimental condition. The comparison of water-collection behavior with other samples showed that the improved efficiency is due to the structure, and wettability induced superior water attraction and removal ability. Moreover, a uniform water condensation under low humidity (28%) is achieved, which has potential applications in harvesting water from arid environments and in high-precision drop control.

Calculation of Water Collection Efficiency Using a Multiphase Flow Solver

This paper reports a new method to calculate water collection efficiency. The method is based on a well-validated multiphase flow solver that solves the Navier–Stokes equations using the projection method on Cartesian grids and uses the moment-of-fluid method to construct the interfaces between different phases. The numerical method is validated against experimental results with good agreement. Using this method, the water collection efficiency of an MS(1)-317 wing is investigated. The current simulations show that the proposed method gives a better prediction of water collection efficiency when large drops are involved. The prediction is attributed to the better modeling of drop and airflow interaction, as well as the consideration of drop splashing.

Fabrication of slippery Zn surface with improved water-impellent, condensation and anti-icing properties

Zinc and its alloys are valuable crucial materials applied in the fields of automobile, ship manufacturing and construction industries. However, their application is limited due to poor performance on water-resistance, condensation and anti-icing property. Slippery liquid-infused porous surface (SLIPS) has been widely used owing to excellent water-repellent, condensation and anti-icing properties. In this work, a SLIPS was fabricated based on zinc substrate by using electrochemical etching, low surface energy modification and lubricant infusion, successively. According to the SEM morphologies and EDS images, it could be confirmed that the rough porous surface structure, low surface energy modification and infused lubricants are key factors accounting for the excellent anti-wetting property of fabricated slippery Zn surface. The experimental results showed that the SLIPS on zinc substrate exhibited outstanding water-repellent performance at a wide range of temperature and drop impact velocity. Moreover, its anti-wetting ability can be sustained even under the impacts of droplets or the continuous water jet. Owing to its dropwise condensation strategy, the SLIPS shows reasonable water collection efficiency, which exceeds 60 mg/(cm2·h) at relative humidity of 90%. The excellent anti-icing property is demonstrated by the simulated ice rain test and deicing force test. And the results showed that only tiny residue ice left on the SLIPS and the deicing force was 2–3 times smaller than ordinary surface. The prepared SLIPS is expected to be an adaptable and efficient method for enhancing the water-repellent, condensation and anti-icing properties of zinc substrate, and may expand the application in energy-efficient fluid handing & transportation, medicine and anti-fouling operating in low temperature environment.

Bioinspired Dual-Tier Coalescence for Water-Collection Efficiency Enhancement.

Directly harvesting water from the atmosphere could aid in negating the issue of fresh water scarcity, garnering increased research interest in recent years. Typically, atmospheric water collection occurs via three main steps: accumulation, transportation, and collection. Although multiple studies have been published on bioinspired structures with enhanced directional fluid transportation, there is a significant lack of designs for enhancing water droplet coalescence. Long mean times before coalescence result in the re-evaporation of microdroplets, severely impeding the efficiency of atmospheric water collection. Herein, a water accumulator derived from a synergistic combination of inspiration from cacti spines and Tillandsia trichomes has been designed to encourage rapid coalescence. The drip-off volume measured in a fog chamber was found to be 220% that of a flat surface within 15 min, suggesting that improving the coalescence efficiency will be important in the future development of water-collection devices.

Water harvesting method via a hybrid superwettable coating with superhydrophobic and superhydrophilic nanoparticles

Water collection gains increasing attention for harvesting atmospheric water in semi-arid deserts and inland areas. A new biomimetic method, inspired by the fog harvesting ability of hydrophobic-hydrophilic surfaces of Namib desert beetles, is presented in this study. It envisages a low-cost preparation (by the photocatalysis of titanium dioxide through ultraviolet irradiation) of a titanium dioxide-silicon dioxide hybrid superwettable surface combining superhydrophobic and superhydrophilic nanoparticles and exhibiting excellent water/fog collection properties. The surface wettability, condensation properties, water collection rate, and wetting stability of the product samples are investigated in detail. The results obtained strongly indicate that the proposed hybrid superwettable surface prepared by maskless photocatalysis enhances the water drop condensation and water collection characteristics, with very stable wettability. The best water collection and drop removal efficiency was experimentally determined at the ultraviolet irradiation time of 200 s. This work findings are considered instrumental in the further design and implementation of hybrid superhydrophobic-superhydrophilic surfaces for cost-efficient atmospheric water harvesting.

Ladderlike Tapered Pillars Enabling Spontaneous and Consecutive Liquid Transport.

Directional liquid transport has significant domestic and industrial applications. Tapered objects have theoretically and experimentally been demonstrated to have the ability to spontaneously transport liquids. However, the transporting distance is limited, and consecutively and spontaneously transporting liquids has always been a challenge. In this work we proposed to exploit ladderlike tapered pillars, which are inspired by relay races, to increase the transport distance. These pillars were designed using a developed numerical model and fabricated by a novel alternating etching and coating method followed by wettability enhancement. We demonstrated through experiments that the resulting pillars could consecutively and spontaneously transport a liquid droplet at an average velocity of 0.139 m/s with a maximum acceleration of 5 g. The optimum window of the tilt angle range (0°-25°), contact angle (50°), and the chemical modification time (5 min) were obtained. Such ladderlike tapered pillars are able to improve the water-collection efficiency. These results may provide a new and systematic way to design and fabricate materials and structures for directional liquid transport.

Experimental evaluation of collection, thermal, and conductivity efficiency of a solar distiller pond as a free concentration unit in wastewater treatment process

AbstractThe performance of one solar pond as a passive step in distilled and potable water production from desalination effluent is surveyed in this research. This solar pond is proposed in a zero discharge desalination process to prevent the salinity shocking which is made by a brackish water stream that exists from desalination units. The solar pond performance is evaluated by measuring three types of efficiency, experimentally, and mathematically. The efficiencies which are defined and calculated from experimental data are conductivity efficiency, thermal efficiency, and water recovery efficiency. The mathematical results are verified by experimental data which has been obtained during a year. The theoretical modelings show very good agreement with experimental data, especially for water collection and conductivity efficiency evaluation. The relative error of theoretical and experimental results for thermal efficiency evaluation through the day and night is obtained 7.2% and 4.9%, respectively.

Computational investigations of water collection efficiency on blades in unsteady vortex flowfield of rotor

To predict ice accretion on the helicopter rotor more accurately, a three-dimensional Eulerian method with a shadow zone dispersion model is developed for calculating the water collection efficiency on blades in the unsteady vortex flowfield of the rotor. Firstly, the unsteady vortex flowfield of the rotor is calculated using a CLORNS code. Secondly, considering the 3-D effect of the rotor deeply, the droplet flowfield on the same embedded grids is solved by the Eulerian method to overcome the defects of traditional 2-D calculation methods for predicting rotor icing. To increase the stability and efficiency of the Eulerian method, the shadow zone dispersion model is presented. Thirdly, the calculated results are respectively validated through the ice amount comparisons with experimental results of UH-1H rotor and SRB rotor. The simulated results show that the blade-tip vortex has a significant effect on the water collection efficiency and causes a drop in the water collection amount along the blade spanwise direction. Finally, the effects of the advance ratio and the forward tilting angle of the rotor shaft on the water collection efficiency are calculated and analyzed, and some new conclusions are obtained. In forward flight, the blade-tip vortex has a more obvious effect on the water collection efficiency in the advancing blade than that in the retreating blade, and this effect decreases with the increase of the advance ratio and the forward tilting angle.