Prediction of the density and viscosity in biodiesel blends at various temperatures

Biodiesel defined as mono-alkyl esters of vegetable oils and animal fats, has had a considerable development and great acceptance as an alternative fuel for diesel engines. Density and viscosity are two important physical properties to affect the utilization of biodiesel as fuel. In this work, mixtures of biodiesel and ultra low sulfur diesel (ULSD) were used to study the variation of density (ρ) and kinematic viscosity (η) as a function of percent volume (V) and temperature (T), experimental measurements were carried out for six biodiesel blends at nine temperatures in the range of 293.15-373.15 K. Both, density and viscosity increases because of the increase in the concentration of biodiesel in the blend, and both of them decrease as temperature increases. One empirical correlation was proposed to estimate the density: ρ = α·V + β·T + δ; and three empirical correlations were developed to predict the kinematic viscosity: η = exp[ln(γ) + ?·V + ω/T + λ·V/T²], η = exp[ln(γ) + ω/T + λ·V/T²] and η = exp[ln(γ) + ω/T + λ·V/T]. The corresponding parameters were optimized by the Levenberg-Marquardt method. The estimated values of density and viscosity are in good agreement with the experimental data because absolute average prediction errors of 0.02% and 2.10% were obtained in the Biodiesel(1) + ULSD(2) system studied in this work.     

Effects of charge density on water splitting at cation-exchange membrane surface in the over-limiting current region

To determine the correlation between surface properties and concentration polarization (CP) behaviors, cation exchange membranes with varying fixed charge densities were prepared and characterized by using several electrochemical analyses such as chronopotentiometry, zeta potential, and current-voltage measurements. Results showed that CP behavior depended mainly on surface charge density. With higher surface charge density, stronger electroconvection was observed, suggesting that an increase in the surface charge density increased the concentration of the counter ions at the membrane surface. As such, the electric field around the membrane surface was strengthened at a current over the limiting current density. Water splitting was also proportional to the surface charge density. This result was consistent with the classical electric field-enhanced water splitting theory, indicating that water splitting increased due to increases in the electric field and prepolarization of water molecules at the membrane-solution interface of the cation-exchange membrane. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Intradiffusion,density and viscosity studies in binary liquid systems of acetylacetone + DMF/DMSO/benzene at 303.15 K and 333.15 K

Intradiffusion coefficients of acetylacetone (AcAc) and DMF/DMSO/benzene in binary systems over the entire concentration range at 303.15 K were determined by ¹H diffusion-order spectroscopy (DOSY) nuclear magnetic resonance (NMR)method based pulse field gradient (PFG). The densities and viscosities of the above three binary systemsat 303.15 Kwere also studied andemployed to calculate the excessmolar volumes (V^E) and deviations in viscosity (Δη). Besides, experiments were carried out at 333.15 K for the systemof AcAc+DMF. The solvent and temperature effect upon the difference in D between enol and keto tautomers, the tautomeric equilibrium and excess properties (V^E and Δη) were discussed as well. Isotherms of VE as a function of mole fraction of AcAc (x₁) show positive deviations in benzene but negative deviations in DMF and DMSO, whereas isotherms of Δη as a function of x₁ record positive deviations in DMF but negative in benzene and DMSO. V^E values show more negative and Δη values are less positive in the system of AcAc + DMF at 333.15 K compared to 303.15 K. The VE and Δη were fitted to a Redlich-Kister type equation and the measured results were interpreted concerning molecular interactions in the solutions.     

Electrochemical study and electrodeposition of manganese in the hydrophobic butylmethylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide room-temperature ionic liquid

The electrochemistry of manganese was investigated at solid disk electrodes in the hydrophobic room-temperature ionic liquid butylmethylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (BuMePy-TFSI) by using staircase cyclic voltammetry and chronoamperometry. The Mn(II) species was introduced into the ionic liquid by anodic dissolution of the metallic manganese electrode. The reduction of Mn(II) ions at tungsten and platinum electrodes accompanies with nucleation mechanism and the coupled oxidation wave encounters kinetic hindrance that results in incomplete reoxidation of Mn electrodeposits. The density and absolute viscosity of BuMePy-TFSI were measured over a temperature range from 301.0 to 348.0 K. A polynomial equation describing the temperature dependence of the density is presented. The viscosity exhibits the Arrhenius temperature dependence and the relevant equation is provided. The manganese coatings were prepared by electrodeposition at several substrates. The surface morphology and X-ray diffraction patterns of these deposits were studied by scanning electron microscopy and powder X-ray diffraction spectroscopy, respectively. The as-electrodeposited manganese coatings were amorphous; however, α-phase manganese was observed after the deposits were annealed under 723 K for 1 day.     

Thermally reversible cross-links in a healable polymer: Estimating the quantity,rate of formation,and effect on viscosity

The conversion behavior of 2MEP4FS, a polymer with thermally reversible Diels–Alder cross-links, is modeled. A processing method is developed to create small, homogeneous prepolymer samples. The glass transition temperature of the prepolymer is estimated using temperature modulated differential scanning calorimetry and equated with the conversion of the polymer. Comparing the measured energy with the literature and computational estimates, the fully cured polymer appears to have a large portion of its moieties unreacted. An autocatalytic model is considered to approximate the reaction rate of 2MEP4FS as a function of conversion and temperature. Outside of the fitted temperature range, the model underpredicts the reaction rates at room temperature and 100 °C. Manual mixing of the monomers is determined to be inadequate to obtain a maximum level of cross-linking. Viscosity measurements made at room temperature and elevated temperatures are correlated with the conversion of the prepolymer.     

An experimental study on single basin double slope simulation solar still with thin layer of water in the basin

Single basin solar still is a popular solar device used for converting available brackish or waste water into potable water. Because of its lower productivity, it is not popularly used. Numbers of works are under taken to improve the productivity of the still. The still productivity depends on parameters like solar radiation intensity, atmospheric temperature, basin water depth, glass cover material, thickness and its inclination, wind velocity and the heat capacity of the still. When compared with other parameters, the basin water depth is the main parameter that affects the performance of the still. For a particular still, the basin water temperature is the function of depth with day variation of solar radiation intensity. In this work a double slope single basin passive type still with basin area of 1.75 m² is fabricated and tested under laboratory conditions for a thin layer of water in the basin. For maintaining thin layer of water basin, it is necessary to spread the water through out the basin by some kinds of wick material or porous materials. In this work, performance of the still is compared by using wick materials like light cotton cloth, light jute cloth and sponge sheet of 2 mm thickness and porous materials like washed natural rock of average size 3/8" × 1/4" and quartzite rock of average size 3/8" as spread materials. The actual solar radiation condition is simulated by 2 kW electrical resistance heater placed below the inner basin. The results show that the still with black light cotton cloth as spread material is found to be more productive. At higher water and glass temperature region, for all basin materials, the production rate increases with the decrease of the difference between the water and glass temperatures for certain period and also the productivity decreases with the increase of water temperature for certain time during this period. Hence the production rate is a complex function of water, glass and the difference between the water and glass temperatures, basin volumetric heat capacity of the material and its porosity.     

Characteristics of subzero startup and water/ice formation on the catalyst layer in a polymer electrolyte fuel cell

This work experimentally explores the fundamental characteristics of a polymer electrolyte fuel cell (PEFC) during subzero startup, which encompasses gas purge, cool down, startup from a subfreezing temperature, and finally warm up. In addition to the temperature, high-frequency resistance (HFR) and voltage measurements, direct observations of water or ice formation on the catalyst layer (CL) surface have been carried out for the key steps of cold start using carbon paper punched with microholes and a transparent cell fixture. It is found that purge time significantly influences water content of the membrane after purge and subsequently cold-start performance. Gas purge for less than 30 s appears to be insufficient, and that between 90 and 120 s is most useful. After gas purge, however, the cell HFR relaxation occurs for longer than 30 min due to water redistribution in the membrane-electrode assembly (MEA). Cold-start performance following gas purge and cool down strongly depends on the purge time and startup temperature. The cumulative product water measuring the isothermal cold-start performance increases dramatically with the startup temperature. The state of water on the CL surface has been studied during startup from ambient temperatures ranging from −20 to −1 °C. It is found that the freezing-point depression of water in the cathode CL is 1.0 ± 0.5 °C and its effect on PEFC cold start under automotive conditions is negligible.     

Numerical simulation of enhancement of mass transfer in the cathode electrode of a PEM fuel cell by magnet particles deposited in the cathode-side catalyst layer

Recent experimental results show that performance of a proton exchange membrane (PEM) fuel cell is improved when small particles of permanent magnet are deposited in the catalyst layer on the cathode side. In this study, the mechanism of this phenomenon was clarified by using numerical simulation. Permanent magnet particles induce a Kelvin (magnetic) repulsive force against liquid water and an attractive force towards oxygen gas. To precisely study the behavior of oxygen and liquid water flows near the interface between the catalyst layer and gas diffuser, the simulation domain included the catalyst layer and gas diffuser. The simulation results revealed the following. The Kelvin repulsive force against liquid water mainly “manages” the liquid water flow and improves the performance of the fuel cell, especially in the current-limited region. In the presence of Kelvin forces, the liquid water saturation near the interface between the catalyst layer and gas diffuser decreases, thus making more pore space available for transport of oxygen gas. Furthermore, the water velocity moving from the interface increases in the upstream region. The gas velocity near the interface also increases, and thus more oxygen is supplied to the reaction sites. In summary, the Kelvin force promotes removal of liquid water from the catalyst layer, thus providing more oxygen to the catalyst and improving the performance of the fuel cell.     

On the work function changes and other properties of the gas-exposed electrode surface in the NEMCA effect

A simple model is developed to describe the backspillover of ionic species at the solid/gas interface as observed in non-Faradaic electrochemical modification of catalytic activity (NEMCA) systems. This model predicts a linear relationship between work function changes and changes in the potential difference at the metal/solid electrolyte interface, as observed experimentally. It also predicts a linear dependence of the surface coverage by ionic species on the potential difference at the metal/solid electrolyte interface, and a linear dependence of the binding energy of adsorbed species on the work function of the gas-exposed catalyst surface.     

A simple model to determine the trends of electric-field-enhanced water dissociation in a bipolar membrane. II. Consideration of water electrotransport and monolayer asymmetry

This work elucidates the mechanism of electric-field-enhanced water dissociation. Particular attention has been given to the influences of water electrotransport and monolayer asymmetry on the water dissociation process. A simple model was proposed with consideration of these two factors and mathematically analyzed in term of thickness ratio, fixed group concentration ratio and water diffusivity ratio of the anion selective layer to the cation selective layer on typical current density curves of bipolar membranes. The results suggest that for practical applications, an asymmetric bipolar membrane with proper ion-exchange capacity and high permeability to water is more effective than a symmetric one. Theoretical simulation values were compared with both the theoretically calculated data by a model without consideration of water electrotransport and the experimental current voltage curves. It is shown that the calculated potential across a bipolar membrane is higher at given current density, which permits a more precise prediction of experimental I–V curves for the case of a bipolar membrane with high water permeability. However, for a bipolar membrane with poorer water permeability, it seems that the calculated value with the model without consideration of water electrotransport is closer to the experimental values, but the model with consideration of water electrotransport can effectively predict the over-limiting current density.     

超滤技术在地表水处理中的应用和研究进展

与常规水处理工艺相比,超滤用于地表水处理时具有低能耗、高效率、占地面积小、不污染环境、易于操控等优点,是解决当代能源、水资源缺乏和环境问题的重要技术.主要从超滤膜的材料,处理地表水的工艺选择,处理水的用途及膜污染等方面总结了超滤在国内外地表水处理中的研究状况,并分析了应用超滤技术处理江河水、湖泊水、及海水淡化方面的优缺点,指出超滤膜在地表水处理中的发展潜力.     

Prediction of the viscosity reduction due to dissolved CO2 of and an elementary approach in the supercritical CO2 assisted continuous particle production of a polyester resin

The dissolution of CO₂ in a polymer causes plasticization of the polymer and hence, its viscosity is reduced. A model based on the free volume theory has been used for a polyester resin, which shows a considerable reduction in the viscosity due to dissolved CO₂. Therefore, supercritical CO₂ has been used as a processing solvent in the continuous production of micron size particles of the resin. Despite the viscosity reduction caused by the dissolved CO₂, an excess quantity of CO₂ with respect to its solubility limit has been used for micronisation of the polymer due to its high viscosity. The mixing of CO₂ and the polymer has not been possible in an extruder at high gas to polymer mass ratios and consequently, a simplified Kenics type static mixer has been used for the mixing purpose. In this study, the effect of various parameters such as temperature, pressure, nozzle diameter and gas to polymer mass ratio on the particle morphology and size has been studied. The experimental results manifest the technological as well as the theoretical insight into the particles production from a high viscosity material.     

Preparation of functionalized and non-functionalized fullerene thin films on ITO glasses and the application to a counter electrode in a dye-sensitized solar cell

Several thin films of [60]fullerene and the derivatives (3-5) have been prepared on ITO glasses by a common coating method using organic solutions and/or by an electrolytic micelle disruption method using surfactants with ferrocenyl moiety 2. In particular, the surface of the film formed by the electrolysis method was confirmed by SEM and AFM measurements, and then these images clearly exhibited that the entire surface of the ITO glass was uniformly covered with [60]fullerene. The UV-vis spectroscopy obviously showed that the thickness increased with the electrolysis time. For example, the thickness of the film formed by the electrolysis for 2 h was ca. 2,000 Å. Furthermore, we investigated the potential utilization as a counter electrode material instead of Pt in a dye-sensitized solar cell (DSC). Consequently, these films, except for that of derivative 5 prepared by the coating process, were found to act as a counter electrode materials in a DSC. These photovoltaic efficiencies of the films prepared by the electric micelle disruption method were higher than those of the films prepared by the common coating method. In addition, the highest efficiency was obtained in the cases with the fullerene thin film formed by the electrolysis for 2 h.     

Theoretical probing of the phenomenon of the formation of the outermost surface layer of a multi-component particle, and the surface chemical composition after the rapid removal of water in spray drying

Spray drying is a primary process for the manufacture of powders, which satisfy a vast array of societal demands in the areas of nutrition, health and medicine. The functionality of a spray-dried product begins with its incorporation into water (wetting followed by dispersion) Therefore, as its surface chemical composition and structure determine its first contact with water (that is, its hydrophilic nature), these are of prime concern. Laboratory studies on this first layer, which is in the order of several nm in depth from the surface, have been extensive but there is still a lack of a fundamental quantitative explanation of it. This has hampered the development of any sort of approach, which would enable industries to predict what the product may be like before conducting costly trials. This current study is an attempt to describe the on-set of solid formation around the outermost layer of a single droplet during the drying process using an innovative ‘conventional’ continuum approach, i.e. diffusion–convection equations, with a few innovative derivations. Though some complexities such as multi-component equations deduced from irreversible thermodynamics, are avoided for simplicity, some comparisons with experimental/industrial results are made. The main feature of this work is that the multi-component effect is combined with the viscosity (at the surface) effect upon the diffusivities of individual components in the solution droplets or suspension droplets. The derivations allow some extended analytical procedures to proceed in order to help make sense of the experimental observations. Comparisons are made against the data published on dairy fluids. This work provides a good basis for a fruitful area of study that will have a positive impact for spray drying industries. In particular, to help this kind of industry to forge ahead into high performing functional particle production, which are becoming increasingly popular.     

Color changes in the surface of granitic materials by consolidated and/or water repellent treatments

Color is one of the parameters to be monitored when determining the suitability of a protective or conservative treatment of stone. Application of a given treatment product should elicit the least possible effect in this parameter. Changes in color of five varieties of granite of highly varying characteristics due to their origin are studied in the present work. All the granites studied are widely used in buildings of historical interest in Avila (Spain). Some varieties are from unaltered facies (grey granites of different grain size), and have a very low degree of porosity, while other are from facies that have undergone strong natural weathering processes, and that display important mineralogical and physical changes. In this sense, the ochre variety of granite contains clays (smectite and some kaolinite); the white variety contains kaolinite and opal, and the red variety contains kaolinite, opal, and iron oxihydroxides. Fresh cut and artificially aged (with 25 cycles of freezing/thawing and cold/heat treatment) samples were treated with consolidant (RC80 or RC70) and/or water repellent (H224) agents. After the corresponding statistical treatment of data obtained, significant changes in ΔE were observed with the treatments given; such changes are more pronounced in unaged samples. Changes in ΔL (lightness), however, despite being noticeable, seem to have only a minor effect on ΔE, which seem to be more dependent on changes in Δa and Δb. This was more pronounced when the stone was treated with RC80 and then with H224. © 1997 John Wiley & Sons, Inc. Cal Res Appl, 22, 133–141, 1997     

Dissolution of hydrogen and the ratio of the dissolved hydrogen content to the produced hydrogen in electrolyzed water using SPE water electrolyzer

Concentration of dissolved hydrogen in electrolyzed water using a solid polymer electrolyte (SPE) water electrolyzer was investigated using a DH-meter. A ratio of the dissolved hydrogen content to an amount of hydrogen concentration calculated from charge passed during electrolysis was estimated. The ratio increased from 10 to 20% with a decrease in current density from 3.0 to 0.3 A dm⁻². The effect of the linear velocity of water on the ratio of dissolved hydrogen was studied. The cross-sectional area of the water channel was changed to change the linear velocity of water. The ratio of dissolved hydrogen increased with increasing the velocity. Due to the fast mass transport by high velocity, the small hydrogen bubbles are fast transferred by the diffusion into the bulk water and dissolved. The population density of the small hydrogen bubbles is found to have an effect on the ratio of the dissolving hydrogen.     

FTIR and electrochemical observation of water content reduction in a thin Nafion film induced by an impregnation of metal complex cations

A thin Nafion^® ion exchange membrane was coated on a graphite electrode, and then impregnated by a metal complex couple of Os(bpy)₃^2+/3+, which served as a typical system to investigate the water content change induced by ion exchange. Cyclic voltammetry and FTIR reflection-adsorption spectroscopic methods were employed to characterize the complex loading, electrochemical behavior of the impregnates inside the film and the water content change. A direct observation of the water content reduction induced by the cation impregnation in the Nafion^® film was achieved. A monotonic relationship between the water reduction percentage and the Os(bpy)₃^2+/3+ loading was also obtained, that is, the heavier the complex loading, the more the water content will be reduced. The FTIR spectroscopic results suggested that the structure of the Nafion^® film could also be changed with water content reduction.     

The evaluation of the polarization resistance in a tubular electrode and its application to the hydrogen electrode reaction

An alternative method for the determination of the kinetic parameters involved in the elementary steps of the reaction mechanism of the hydrogen electrode reaction is proposed. It is based on the determination of the variation of the polarization resistance in a tubular platinum electrode with a laminar flow of electrolyte as a function of the activity of protons of the electrolyte solution. A theoretical expression that relates the experimental variables and the equilibrium polarization resistance is developed, which takes into account the current distribution along the electrode surface. The results are compared with others obtained previously, contributing to the verification of the kinetic mechanism through a completely different experimental procedure.