Free Evaporation Research Articles

Cooking-Inspired Versatile Design of an Ultrastrong and Tough Polysaccharide Hydrogel through Programmed Supramolecular Interactions.

Simultaneously achieving strength and toughness in soft materials remains a challenge, especially for physically crosslinked hydrogels with many inactive interaction sites. In this work, inspired by the cooking of thick soup in China, a facile method that includes free water evaporation of the diluted pregel solution followed by crosslinking (WEC) is proposed to fabricate polysaccharide hydrogels. Herein, without the constraints of viscosity and crosslinking, polymer chains can homogenously approach as much as possible, thereby enabling the transformation of inactive supramolecular interaction (H-bonding and ionic coordination) sites into active sites until reaching the maximum level. Through facilely tuning the concentrating degree, programmed supramolecular interactions, serving as energy-dissipating sacrificial bonds, impart the hydrogels with strength and toughness over a very wide range, where a "ductile-to-tough" transition is discovered to occur first. Using WEC in alginate, the concentration can be as high as 25 wt% without sacrificing processing ability, a result that is significantly beyond common value (3-7 wt%), and the extremely stiff and tough hydrogels are obtained, superior to isotropic alginate hydrogels ever reported. This research offers a facile and versatile strategy to fabricate isotropic polysaccharide hydrogels, which become ideal matrix materials for further fabrication of hybrid or anisotropic hydrogels.

An Immersed Boundary Method for flows with evaporating droplets

We present a new Immersed Boundary Method (IBM) for the interface resolved simulation of spherical droplet evaporation in gas flow. The method is based on the direct numerical simulation of the coupled momentum, energy and species transport in the gas phase, while the exchange of these quantities with the liquid phase is handled through global mass, energy and momentum balances for each droplet. This approach, applicable in the limit of small spherical droplets, allows for accurate and efficient phase coupling without direct solution of the liquid phase fields, thus saving computational cost. We provide validation results, showing that all the relevant physical phenomena and their interactions are correctly captured, both for laminar and turbulent gas flow. Test cases include fixed rate and free evaporation of a static droplet, displacement of a droplet by Stefan flow, and evaporation of a hydrocarbon droplet in homogeneous isotropic turbulence. The latter case is validated against experimental data, showing the feasibility of the method towards the treatment of conditions representative of real life spray fuel applications.

KARAKTERISTIK MUTU FISIK TEKWAN KERING DENGAN RASIO IKAN BERBEDA

Dried tekwan is a traditional restructured-fish product of South Sumatera processed by convectional drying. The study aimed to determine the effect of fish and tapioka ratio and tekwan’s length on the physical quality of the dried tekwan. The physical quality of dried tekwan made with different ratio of fish and tapioca ratio (1:1, 1.5:1 and 2:1 (w:w)) and length 1, 2, and 3 cm were investigated. The physical quality evaluated were the degree of whiteness, rehydration ratio, water holding capacity (WHC) and microstucture. The drying profile and proximate composition were also evaluated. There was no difference in the rate of drying of different fish:tapioca ratio as well a different tekwan length when free water evaporation was progressing. However, difference in drying rate was observed when the water content reached the equilibrium. Ratio 2:1 of fish and tapioca and 2 cm length of tekwan was found the to be best treatment and resulting in dried tekwan with moisture content 10.22%, ash 1.9%, protein 27.9%, fat 1.38%, carbohydrate 58.6%, whiteness 45.96% and expressible moisture content 2.06%. Microstructure of dried tekwan with 2:1 ratio showed more compact structure and slight damage than 1.5:1 ratio. However, dried tekwan with 2:1 ratio still had lower rehydration properties than other treatment.

Kinetics of evaporation under vacuum in preparation of solar-grade silicon by electron beam melting

A kinetics model for silicon evaporation is established in order to investigate the dependence of temperature and chamber pressure on silicon loss. The results show that the rate-limiting step is mass transfer of silicon in gas phase at low temperature; while it transits to free evaporation on melt surface as the temperature rises. As for electron beam melting process, silicon free evaporation is considered as the rate-limiting step due to the extremely high temperature of the melt. The relationship between impurity removal efficiency and silicon loss is obtained according to this calculation model. The silicon loss ratio is less than 10% when the removal efficiency of phosphorus is close to 100%, but that of aluminum is still low, indicating this technology is more effective for the removal of phosphorus. Aluminum can be further removed by increasing temperature or prolonging refining time, but leading to more silicon loss.

Experimental Investigation about the Parameters that Effect on Evap-oration from Sub-storage Reservoir

Management of water resources become one of the most important subjects in the human's life. The water sustains life on earth, therefore; more care for water management is necessary. In the last years, studies show water use will be more in the world as result of rapid increase in population, industrialization, and urbanization etc. The evaporation losses from dam's reservoirs and lagoon form very huge losses in water resources. The annual evaporation depth losses in Iraqi Western Desert is about (2.25 -3) meter, this depth store the highest percentage of the small dams. Sub-surface storage reduces evaporation losses and maintains water quality by minimizing salt concentration. In present study, three tanks are used to simulate the subsurface reservoirs to study the effectiveness of underground storage on reducing the evaporation loss. Each tank have squares cross section tanks of (80) cm length and (40) cm depth and filled up to (34) cm with different graded soil (labeled as A, B with coarse soil, and D with fine soil) to simulate the storage below the ground. While the forth tank filled with water (labeled as C) to represent the reservoir of direct evaporation for comparison study. The present study considers three parameters that can controlled the evaporation from subsurface reservoirs: (a) temperature variation, (b) water table variation, and (c) material properties such as porosity. The field study continues for four months, it was started at Jun.11, 2016 and ended at Dec. 15, 2016 in the Erbil city at north of Iraq. The results showed evaporation losses are reduced by using subsurface storage reservoir with gravel in comparison with free surface evaporation. The evaporation losses are reduced about 46 % , 39% , 64% when the water table below gravel surface range from 5 to 10 cm , while at 20 cm depth of the water table the evaporation reduction is about (85 % to 86% 95%) from A, B and D tanks with porosity 0.65 ,0.67 and o.35 for A ,B and D tanks, respectively..

Additive-free synthesis of robust monolithic mesoporous silica support used in catalysis

Use of mesoporous silica as functional material or as support in adsorption and catalysis has been very limited in commercial terms due to limitations of powder morphology and accompanied handling and recycling issues. Previous reports on preparations of monolithic mesoporous silica generally indicate complicated procedures and/or deterioration of final structure. In this research, a simple scalable one-pot sol-gel synthesis with subsequent free atmospheric evaporation is applied to prepare monolithic mesoporous silica (of MSU family). Effects of synthesis parameters such as reagent concentrations and additives on both nano-structure and physical stability of the monolith were investigated. No-additive synthesis resulted in the most robust monolith under mechanical handling and hydrodynamic conditions. Material's disintegration rate in agitated water was as low as 0.1 mg/h and its structural stability was approved under hydrothermal conditions. The monolithic mesoporous silica samples functionalized with acid and base surface groups were used independently in catalytic esterification and transesterification reactions. At relatively low temperatures (~ 50 °C), conversion of stearic acid to ethyl stearate was completed in the presence of monolithic acid catalyst. At the same conditions, above 50% and 20% conversions of triacetin to ethyl acetate (as a typical biodiesel production method) were achieved in the presence of monolithic acid and base catalysts respectively.

An Indirect Method for Vapor Pressure and Phase Change Enthalpy Determination by Thermogravimetry

Vapor pressure is a fundamental property of a pure substance. This property is the pressure of a compound’s vapor in thermodynamic equilibrium with its condensed phase (solid or liquid). When phase equilibrium condition is met, phase coexistence of a pure substance involves a continuum interplay of vaporization or sublimation to gas and condensation back to their liquid or solid form, respectively. Thermogravimetric analysis (TGA) techniques are based on mass loss determination and are well suited for the study of such phenomena. In this work, it is shown that TGA method using a reference substance is a suitable technique for vapor pressure determination. This method is easy and fast because it involves a series of isothermal segments. In contrast to original Knudsen’s approach, where the use of high vacuum is mandatory, adopting the proposed method a given experimental setup is calibrated under ambient pressure conditions. The theoretical framework of this method is based on a generalization of Langmuir equation of free evaporation: The real strength of the proposed method is the ability to determine the vapor pressure independently of the molecular mass of the vapor. A demonstration of this method has been performed using the Clausius–Clapeyron equation of state to derive the working equation. This algorithm, however, is adaptive and admits the use of other equations of state. The results of a series of experiments with organic molecules indicate that the average difference of the measured and the literature vapor pressure amounts to about 5 %. Vapor pressure determined in this study spans from few mPa up to several kPa. Once the p versus T diagram is obtained, phase transition enthalpy can additionally be calculated from the data.

Vaporization behavior of an alkyl diphenyl ether and a commercial lubricant

The equilibrium vapor pressure as a function of temperature for an alkyl diphenyl ether with a vaporization coefficient significantly smaller than unity was characterized using the combined Langmuir free evaporation and mass loss Knudsen effusion technique. Results are compared using different cell designs and discrepancies, difficulties, and complications are discussed. The enthalpy and entropy of vaporization are estimated using the average temperature of the measurements.

Synthesis of SnS and ZnS Hollow Microarchitectures Decorated with Nanostructures and Their Photocatalytic Behavior for Dye Degradation

AbstractSnS and ZnS hollow microarchitectures decorated with nanostructures were synthesized by catalysis free thermal evaporation technique using metal microwires and sulfur powder as starting materials. For SnS, we observed a microtube formation comprised of a thin metallic Sn layer in the inner surface, SnS orthorhombic structure thick layer with SnS nanostructures on the top. For ZnS, we found out the formation of hollow sphere with a thin metallic layer in the inner part, a thick cubic phase layer of ZnS, and on this second phase, nanostructures of ZnS hexagonal crystal phase grew up homogeneously. The surface tension, intrinsic to liquids, induces the formation of a microsphere in ZnS sample in order to minimize the surface area. ZnS and SnS hollow semiconducting microstructures have exhibited efficient activity to degrade the methylene blue under simulated sunlight irradiation. The results reveal that ZnS microstructures have higher photoactivity to organic degradation when compare to SnS in the same time interval. The observed results demonstrate the potential of thermal evaporation process without any catalyst material as a simple, fast and efficient route to obtain hollow hierarchically micro/nano architectures of SnS and ZnS with enhanced photocatalytic activity.

Effects of soil characteristics on moisture evaporation

Evaporation of water from soils is a three-stage process that has great significance in stress development in exposed geotechnical structures, generation of dusts that can cause environmental pollution and respiratory ailments, and dereliction of land by generating drought conditions. In this study, the factors that influence water evaporation from soil have been divided into two categories: external, referring to atmospheric conditions and interior, covering surficial soil characteristics and water content conditions. Particularly, five different sets of laboratory based evaporation tests were performed using cylindrical (150 mm diameter and 7–28 mm height) samples of clayey soil mixed with quartzite sands (three grainsize ranges: 0.2–0.5 mm, 0.5–1.0 mm, and 2.0–3.0 mm) in weight proportions ranging from 0% to 50% to evaluate the effects of soil texture, mineralogy and initial compactive state on its free water evaporation process at room temperature (20–22 °C) and relative humidity (50 ± 2%) conditions. The evaporation tests were performed using mass loss measurements on soil samples to an accuracy of 0.01 g. Findings show that in the first stage of soil drying, water content decreases continuously with time while the ratio of actual to potential evaporation, Ea/Ep stays mostly stable. During the falling rate stage, both water content and Ea/Ep decrease significantly. However, the water content varies but not significantly due to the low value of residual evaporation rate in the residual evaporation stage. Soil with lower sand content starts the falling rate stage at higher water content: 32.52% at added sand proportions of 0% versus 21.87%, 20.65%, 20.45%, 20.26% and 18.34% at added sand proportions of 10%, 20%, 30%, 40%, and 50% respectively. Larger soil sample thicknesses accelerate water evaporation rate and extend the constant evaporation rate stage. Soil particle size was not found to have significant impact on evaporation rate on per unit weight of added soil basis. The evaporation rate increases in direct proportionality to increase in initial water content and dry density.

Growth and characterization of pure and Ca2+ doped MnHg(SCN)4 single crystals

Manganese-mercury thiocyanate, MnHg(SCN)4, crystal is considered to be an important organometallic nonlinear optical (NLO) material exhibiting higher thermal stability and second harmonic generation (SHG) efficiency. In order to understand the effect of Ca2+ as an impurity on the physicochemical properties, we have grown pure and Ca2+ doped (with a concentration of 1 mol%) MnHg(SCN)4 single crystals by the free evaporation of solvent method and characterized structurally, chemically, optically and electrically by adopting the available standard methods. Results obtained indicate that Ca2+ doping increases significantly the optical transmittance, SHG efficiency, and DC electrical conductivity and decreases the dielectric loss factor (improves the crystal quality), and AC electrical conductivity without distorting the crystal structure. Also, the low dielectric constant (εr) values observed for both the pure and doped crystals considered at near ambient temperatures indicate the possibility of using these crystals not only as potential NLO materials (useful in the photonics industry) but also as promising low εr value dielectric materials (useful in the microelectronics industry).

Vaporization of water droplets with non-metallic inclusions of different sizes in a high-temperature gas

Experimental research on mechanisms of vapor production by boiling and evaporation was carried out on heterogeneous droplets of water containing graphite particles of different sizes and concentrations, heated by high-temperature environment (up to about 1373 K). Different steps have been observed, such as free surface evaporation of the droplet, bubbles boiling at the solid inclusion/liquid interface, the explosive disintegration of a drop into a cluster of small droplets and efficient evaporation of the produced smaller droplets. We proposed the conditions for the appearance of this explosive breakup of droplets. The present paper reports that the addition of small graphite particles into heterogeneous droplets can reduce their lifetimes by about 50% in this type of high-temperature environment. Moreover, this facilitated the explosive breakup of droplets, allowing intense vaporization. This behavior led us to make the hypothesis that an insulating layer of vapor appears at the outside droplet surface and at the interface between the solid inclusions and the droplet. Measurements on the explosive breakup of heterogeneous water droplets have allowed establishing an increase of the evaporation surface area by almost fifteen times, as compared to the initial surface of droplets. However, when using graphite suspension, the measured increase of the evaporation surface was not larger than threefold. The evaporation surface area during the explosive breakup of water-graphite suspensions was 5.4 smaller as compared to water without impurities. We reported on the reasons for the above differences. The results are useful for developing technologies of fire extinguishing by using water sprays containing non-metallic solids. Practical implementation of the explosive breakup of heterogeneous droplets can eventually permit extinguishing fire on larger areas with an identical water load.

Hanging colloidal drop: A new photonic crystal synthesis route

High-quality photonic crystals (hundreds of micrometres in thickness) were grown by the free evaporation of a colloidal drop consisting of silica and polystyrene nanospheres with dimensions of 300 nm, 500 nm, and 1000 nm. The essence of experimental findings is that the drop has to hang on a pillar. This leads to the inhibition of the droplet spreading, the minimisation of the convective force, and the zeroing of the static frictional force between nanospheres and the liquid/air interface, where the first layer is formed. The theoretical essence is the continuous adjustment of nanospheres positions during the growth of photonic crystal, a key condition of the self-assembling phenomenon.

Growth and characterization of metal doped and quasi mixed crystals based on ZnCd(SCN)4

In order to understand the effect of forming hybrid crystals by doping with metallic impurities or by quasi mixing on the physicochemical properties of the basic material crystal, we have grown by the free evaporation method at room temperature and characterized (chemically, structurally, optically and electrically) un-doped and K+/Ca2+/Mn2+/Mg2+/Cu2+ doped (with 1 mol% concentration) ZnCd(SCN)4 and ZnxCd(2-x)(SCN)4 (with x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) single crystals. Single crystals could be grown with x = 0.0 (leading to Cd(SCN)2) but not when x = 2.0 (leading to Zn(SCN)2). Results obtained in the present study through X-ray diffraction and EDAX spectral measurements indicate the formation of the above hybrid crystals. The optical (UV–Vis-NIR spectral and SHG efficiency) measurements indicate significant changes in optical transmittance and SHG efficiency due to doping as well as quasi mixing. Dielectric measurements made in the temperature range 40–150 °C with a fixed frequency of 1 kHz indicate a normal dielectric behavior for all the eleven crystals grown. Moreover, the present study indicates an increase of dielectric constant and SHG efficiency when ZnCd(SCN)4 crystal is doped with a metallic impurity whereas a decrease of dielectric constant and SHG efficiency when quasi mixing is done.

Variation characteristics and influencing factors of free water evaporation in recent 58 years in Tai’an area

The mutation test and trend analysis of free water evaporation in Tai’an from 1956 to 2013 were carried out with Pettitt detection method, Mann-Kendall method and linear tendency estimation method. The results indicate that: (1) the free water evaporation in Tai’an was distributed unevenly within the year, and the maximum appeared in June, accounting for 14.5% of the whole year; (2) in the last 58 years, the free water evaporation in Tai’an changed significantly in 1985. The evaporation decreased obviously before the change, then fluctuated around the mean value, and gradually became stable; (3) by means of correlation analysis and partial differential decomposition, it was found that free water evaporation in Tai’an before 1985 was positively correlated with air temperature, solar radiation and wind speed, and negatively correlated with actual water vapor pressure. The significant decrease in solar radiation and wind speed are the main reasons for the significant decline in annual evaporation; (4) after 1985, the air temperature played a dominant role, and the rise of air temperature offset the negative influence of decline of wind speed and solar radiation on the free water evaporation.

Dynamic Analysis of the Temperature and the Concentration Profiles of an Industrial Rotary Kiln Used in Clinker Production.

Cement is one of the most used building materials in the world. The process of cement production involves numerous and complex reactions that occur under different temperatures. Thus, there is great interest in the optimization of cement manufacturing. Clinker production is one of the main steps of cement production and it occurs inside the kiln. In this paper, the dry process of clinker production is analysed in a rotary kiln that operates in counter flow. The main phenomena involved in clinker production is as follows: free residual water evaporation of raw material, decomposition of magnesium carbonate, decarbonation, formation of C3A and C4AF, formation of dicalcium silicate, and formation of tricalcium silicate. The main objective of this study was to propose a mathematical model that realistically describes the temperature profile and the concentration of clinker components in a real rotary kiln. In addition, the influence of different speeds of inlet gas and solids in the system was analysed. The mathematical model is composed of partial differential equations. The model was implemented in Mathcad (available at CCA/UFES) and solved using industrial input data. The proposal model is satisfactory to describe the temperature and concentration profiles of a real rotary kiln.

Example of a Fluid-Phase Change Examined with MD Simulation: Evaporative Cooling of a Nanoscale Droplet.

We carried out a series of molecular dynamics simulations in order to examine the evaporative cooling of a nanoscale droplet of a Lennard-Jones liquid. After thermally equilibrating a droplet at a temperature Tini/Tt ≃ 1.2 (Tt is the triple-point temperature), we started the evaporation into vacuum by removing vaporized particles and monitoring the change in droplet size and the temperature inside. As free evaporation proceeds, the droplet reaches a deep supercooled liquid state of T/Tt ≃ 0.7. The temperature was found to be uniform in spite of the fast evaporative cooling on the surface. The time evolution of the evaporating droplet properties was satisfactorily explained with a simple one-dimensional phase-change model. After a sufficiently long run, the supercooled droplet was crystallized into a polycrystalline fcc structure. The crystallization is a stochastic nucleation process. The time and the temperature of inception were evaluated over 42 samples, which indicate the existence of a stability limit.

Growth by free evaporation method and physico - chemical properties of calcium succinate single crystals

Calcium succinate single crystals were grown by adopting the free evaporation method for the first time and characterized. Powder X-ray diffraction, FTIR spectral and thermo-gravimetric measurements were carried out to characterize the grown crystals structurally, chemically and thermally. Optical characterization has been done by UV–vis–NIR spectral and second harmonic generation efficiency measurements. Microhardness and dielectric measurements were carried out to characterize mechanically and electrically. The results obtained indicate that the grown crystals exhibit good crystallinity, triclinic lattice structure, reasonable thermal stability (up to 68°C), good transmittance (in the wavelength range from 240 to 1200nm), second harmonic generation, mechanical softness and normal dielectric behavior.

Effect of ambient odor on cognitive functions in children

We studied the effect of the peppermint ambient odor on the performance of routine Russian school language tests by primary-school students in a standard classroom, where a noiseless source of odor provided scenting the air by means of free evaporation of the essential oil at a constant low concentration. It is shown that in the presence of peppermint odor the marks for a word dictation test that is based on the longterm memory are significantly higher than in the absence of the odor, whereas the performance of text copying test (based mainly on attention) is not influenced by the presence of peppermint odor.

Assessment of various vaporisation methods related for reservoir in the Northern Region of Gujarat, India

Evaporation from water surfaces as an essential component for efficient management of reservoirs, particularly in water-scarce areas in India. Evaluating performance of seven empirical methods based on ten years meteorological data, the most effective and reliable evaporation estimates model for Dharoi reservoir (India) has been derived while comparing monthly, yearly and seasonal basis with observed pan values. The various goodness of fit measures, such as; coefficient of determination (R2), index of agreement (D), root mean square error (RMSE), and relative bias (RB) have been chosen for the performance evaluation. After application of correction factor in Penman, the value of R2, RSME, RB and D are 0.81, 0.61, 0.10 and 0.94 respectively shows good agreement with Pan value. Other models are showing good fitness with Pan but, the parameters considered in Penman is more and important for evaluation of evaporation. Hence Penman method can successfully be extensive for free water surface evaporation estimates in Dharoi reservoir, part of semi-arid region of Gujarat, India.