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could sumrizied these point for each one sparately. T.q
1. Study of viscosity and specific heat capacity characteristics of water-based Al2O3 nanofluids at low particle concentrations
In this paper, the specific heat capacity and viscosity properties of water-based nanofluids containing alumina nanoparticles of 47 nm average particle diameter at low concentrations are studied. Nanofluids were prepared with deionised water as base fluid at room temperature by adding nanoparticles at low volume concentration in the range of 0.01%–1% to measure viscosity. The effect of temperature on viscosity of the nanofluid was determined based on the experiments conducted in the temperature range of 25C to 45C. The results indicate a nonlinear increase of viscosity with particle concentration due to aggregation of particles. The estimated specific heat capacity of the nanofluid decreased with increase of particle concentration due to increase in thermal diffusivity. Generalised regression equations for estimating the viscosity and specific heat capacity of nanofluids for a particular range of particle concentration, particle diameter and temperature are established.
Y. Raja Sekhara & K.V. Sharma, Journal of Experimental Nanoscience, Vol.04, 2013, pages: 1-17
2. Measurements of the heat capacity of an azeotropic mixture of water, ethanol and toluene from 79 to 320 K
The molar heat capacity of the azeotropic mixture composed of 0.329 water, 0.397 ethanol, and 0.274 toluene, was measured by adiabatic calorimetry in the temperature range 79–320 K. The glass transition and phase transitions of the mixture were determined from the curve of the heat capacity with respect to temperature. The glass transition occurred at (108.4 ± 0.2) K. The phase transitions took place in the temperature range of 129–155 K corresponding to the solid–solid and solid–liquid phase transitions of ethanol, water and toluene, respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to standard temperature 298.15 K were derived from the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.
Zhaodong Nan & Zhi-Cheng Tan, Fluid Phase Equilibria, Vol. 226, 2004, pages: 65-70
3. Distillation profiles in ternary heterogeneous mixtures with distillation boundaries: staged columns
Distillation boundaries originate from saddle azeotropes, dividing the composition space into distillation regions. In heterogeneous mixtures distilled in packed columns, distillation regions overlap. The common area of distillation regions is parametrically sensitive, and it determines the possibilities of crossing (at a finite reflux) the distillation boundaries defined for a total reflux or reboil ratio. This work is an extended research of the paper (Królikowski et al., 2011) conducted to scrutinize whether the distillation regions overlapped in heteroazeotropic systems distilled in staged columns. Presented studies were performed by finding such composition points of the products, for which the rectifying profiles of staged columns were ended in different distillation regions. Calculations were executed for the heterogeneous mixture classified under Serafimov’s topological class as 3.1-2: ethanol – benzene – water. Distillation regions for staged columns were found to overlap each other in the heterogeneous systems. As a result, their common part was parametrically sensitive.
Andrzej Ryszard Królikowski, Chemical and Process Engineering, Vol.33 (2), 2012, pages: 207-219
4. Heterogeneous batch extractive distillation of minimum boiling azeotropic mixtures
Following previous studies on heterogeneous batch azeotropic distillation, we evaluate the use of heterogeneous entrainers for the separation of binary azeotropic mixtures by extractive distillation. This process is well suited for systems where the entrainer forms a saddle heteregeneous azeotrope with anyone of the original components, such systems being unsuitable for non extractive heterogeneous batch distillation processes. Process feasibility is assessed from the isovolatility curves and the volatility order diagram. It tells us whether the homogeneous original component or the heteroazeotrope is drawn at the column top and establishes the distillation tasks sequence using a batch rectifying column. The theoretical insights are validated via rigourous simulation for the separation of the mixture acetonitrile – water with hexylamine or butyl acetate. Finally, the same method is applied for the theoretical analysis of a reported industrial example where water is used for the separation of binary organic mixture leading to a complex ternary system with several binary azeotropic points and a homogenous ternary azeotrope.
Rodríguez Donis Ivonne et. al., AIChE Journal, Vol. 49(12), 2003, pages: 3074-3083
5. Heterogeneous Batch Distillation Processes: Real System Optimisation
In this paper, optimisation of batch distillation processes is considered. It deals with real systems with rigorous simulation of the processes through the resolution full MESH differential algebraic equations. Specific software architecture is developed, based on the BatchColumn® simulator and on both SQP and GA numerical algorithms, and is able to optimise sequential batch columns as long as the column transitions are set. The efficiency of the proposed optimisation tool is illustrated by two case studies. The first one concerns heterogeneous batch solvent recovery in a single distillation column and shows that significant economical gains are obtained along with improved process conditions. Case two concerns the optimisation of two sequential homogeneous batch distillation columns and demonstrates the capacity to optimize several sequential dynamic different processes. For such multiobjective complex problems, GA is preferred to SQP that is able to improve specific GA solutions.
Pommier Sébastien et. al. , Chemical Engineering and Processing, Vol. 47(3), 2008, pages: 408-419,
6. Density, viscosity, and surface tension of water+ethanol mixtures from 293 to 323K
Density, viscosity, and surface tension of liquids are important physicochemical properties which affect mass and heat transfer in solutions. The density, viscosity, and surface tension of binary mixture of water+ethanol at 293, 298, 303, 308, 313, 318, and 323 K are reported and compared with the available literature data. The findings of these comparisons show how the measured data are reproducible from different laboratories. The molar volume of water+ ethanol mixtures are also calculated using measured density values. The Jouyban-Acree model was used for mathematical correlation of the data. The relative deviation (RD) was used as an error criterion and the RD values for correlation of density, viscosity, surface tension and molar volume data at investigated temperatures are 0.1±0.1%, 10.4±9.5%, 4.2±3.6%, and 0.3±0.3%, respectively. The corresponding RDs for the predicted properties after training using the experimental data at 298 K are 0.2±0.2%, 14.1±15.8%, 5.4±4.6% and 0.4±0.3%, respectively, for density, viscosity, surface tension, and molar volume data. This study shows that the Jouyban-Acree model can correlate/predict physicochemical properties of the mixtures of solvents at different temperatures with acceptable error in calculation.
Ibrahim Sadek Khattab et. al., Korean Journal of Chemical Engineering, Volume 29 (6), 2012, pages: 812-817
7. Evaporation of Ethanol-Water Mixture Drop on Horizontal Substrate
This study investigates the evaporation of sessile drop comprising ethanol and water mixture on horizontal poly methyl methacrylate surface. The contact angle () and contact radius (R) of ethanol-water mixture drop are recorded with time, considering the impacts of presence of ethanol. With excess ethanol, the drop evaporation is principally controlled by a phase in which both the contact angle and contact radius are falling. A diffusional model assuming linear relation between contact radius and time is proposed as = eR 3 + cR 1, where e and c denote fitting coefficients. This model correlates with the experimental data.
Zhen Wang et. al., Drying Technology Vol. 26(6), 2008, pages: 806-810
8. The Flow Characteristics of an Evaporating Ethanol Water Mixture Droplet on a Glass Substrate
Droplet evaporation has attracted much interest recently, being relevant to a wide range of biological and technological applications. The underlying mechanisms for this phenomenon are still poorly understood. We report on experimental results, from micro-Particle Image Velocimetry (µPIV), of the spatial and temporal velocity field within pure water and ethanol-water mixture droplets evaporating on a glass substrate. The drop profile, evaporation rate and surface temperature were also measured. For pure water droplets, the redial velocity is found to exhibit a maximum spatially towards the three-phase contact line and to increase dramatically towards the end of the drop lifetime. For ethanol-water droplets, three flow phases of (I) vortical flow, (II) transient flow and (III) radial flow were observed. Phase I has vortices, driven, we believe, by concentration differences arising during the preferential evaporation of ethanol. Phase II sees an exponential decay in vorticity with remaining vortices migrating towards the contact line, accompanied by the formation of one large toroidal vortex, possibly due to ethanol depletion at the apex of the drop leading to a surface tension instability. Phase III is characterized by radial flow towards the contact line, matching the evaporative flux and identical to the flow measured for pure water.
Yoshinori Hamamoto et. al., Journal of Thermal Science and Technology, Vol. 7(3), 2012, pages: 425-436.
9. Evaporation phase change processes of water/methanol mixtures on superhydrophobic nanostructured surfaces
Evaporation phenomena are a critical and frequently seen phase change process in many heat transfer applications. In this paper, we study the evaporation process of a sessile droplet on two topologically different surfaces, including smooth and nanostructured surfaces. The nanostructured surface has an array of high-aspect-ratio nanowires (height/diameter ~ 125) and is implemented by using a simple template-based nanofabrication method. It possesses superhydrophobicity (>140°) and low contact angle hysteresis (1.2–2.1°), allowing the liquid droplets to remain in the 'fakir' state throughout the evaporation processes. Sessile droplets of deionized (DI) water and water/methanol binary mixture test liquids with their contact angles and base diameters are monitored. The results show that the nanostructures play a critical role in the droplet dynamics during evaporation.
Cheng-Kun Chiang et. al., Journal of Micromechanics and Microengineering, Vol. 21(7), 2011, pages: 075003 (8pp)
10. Analysis of the effects of evaporative cooling on the evaporation of liquid droplets using a combined field approach
During liquid evaporation, the equations for the vapor concentration in the atmosphere and for the temperature in the liquid are coupled and must be solved in an iterative manner. In the present paper, a combined field approach which unifies the coupled fields into one single hybrid field and thus makes the iteration unnecessary is proposed. By using this approach, the influences of the evaporative cooling on the evaporation of pinned sessile droplets are investigated, and its predictions are found in good agreement with the previous theoretical and experimental results. A dimensionless number Ec which can evaluate the strength of the evaporative cooling is then introduced, and the results show that both the evaporation flux along the droplet surface and the total evaporation rate of the droplet decrease as the evaporative cooling number Ec increases. For drying droplets, there exists a critical valueEcCrit below which the evaporative cooling effect can be neglected and above which the significance of the effect increases dramatically. The present work may also have more general applications to coupled field problems in which all the fields have the same governing equation.
Xuefeng Xu et. al., Scientific Reports, Vol. 5, 2015, article no. 8614
Explanation / Answer
Dear Student,
1. Study of viscosity and specific heat capacity characteristics of water-based Al2O3 nanofluids of 47 nm average particle diameter at low particle concentrations. Nanofluids were prepared with deionised water at low volume concentration in the range of 0.01%–1% to measure viscosity. The estimated viscosity of the nanofluid increased with particle concentration due to aggregation of particles. The estimated specific heat capacity of the nanofluid decreased with increase of particle concentration due to increase in thermal diffusivity.Equations for estimating the viscosity and specific heat capacity of nanofluids for a particular range of particle concentration, particle diameter and temperature are established.
2. Measurements by adiabatic calorimetry of the molar heat capacity of an azeotropic mixture of 0.329 water, 0.397 ethanol and 0.274toluene from 79 K to 320 K. The glass transition occurred at (108.4 ± 0.2) K and phase transitions in the temperature range of 129–155 K of the mixture was determined from the curve of the heat capacity with respect to temperature. The thermodynamic functions of the mixture at 298.15 K were derived from the relationship of the thermodynamic function and the function of the measured heat capacity with respect to temperature.
3.Distillation regions for staged columns were found to overlap each other in the heterogeneous systems. As a result, their common part was parametrically sensitive. It determines the possibilities of crossing the distillation boundaries defined for a total reflux or reboil ratio. Presented studies were performed by finding such composition points of the products, for which the rectifying profiles of staged columns were ended in different distillation regions. Calculations were executed for the heterogeneous mixture classified under Serafimov’s topological class as 3-1-2 : ethanol – benzene – water.
4. Based on the previous studies, we evaluate the use of heterogeneous entrainers for the separation of binary azeotropic mixtures by extractive distillation. The system where the entrainer forms a saddle heterogeneous azeotrope with anyone of the original components is unsuitable for non extractive heterogeneous batch distillation processes. Process feasibility is assessed from the isovolatility curves and the volatility order diagram The theoretical insights are validated via rigourous simulation for the separation of the mixture acetonitrile – water with hexylamine or butyl acetate. Finally, the same method is applied for the theoretical analysis of a reported industrial example where water is used for the separation of binary organic mixture leading to a complex ternary system with several binary azeotropic points and a homogenous ternary azeotrope.
5. Optimisation of batch distillation deals with real systems for which specific software architecture is developed, based on the BatchColumn® simulator and on both SQP and GA numerical algorithms, and is able to optimise sequential batch columns as long as the column transitions are set. The efficiency of the proposed optimisation tool is illustrated by two case studies. The first one concerns heterogeneous batch solvent recovery in a single distillation column and the second one concerns the optimisation of two sequential homogeneous batch distillation columns. For such multiobjective complex problems, GA is preferred to SQP that is able to improve specific GA solutions.
6. Density, viscosity, and surface tension of water+ethanol mixtures from 293 K to 323K are reported and compared with the available literature data.The findings of these comparisons show how the measured data are reproducible from different laboratories. The molar volume of water+ ethanol mixtures are also calculated using measured density values. The RD values for correlation of density, viscosity, surface tension and molar volume data at investigated temperatures are 0.1±0.1%, 10.4±9.5%, 4.2±3.6%, and 0.3±0.3%, respectively. The corresponding RDs for the predicted properties using the experimental data at 298 K are 0.2±0.2%, 14.1±15.8%, 5.4±4.6% and 0.4±0.3%, respectively, for density, viscosity, surface tension, and molar volume data. This study shows that the Jouyban-Acree model can correlate/predict physicochemical properties of the mixtures of solvents at different temperatures with acceptable error in calculation.
7. The study investigates the evaporation of ethanol and water mixture on horizontal poly methyl methacrylate surface. The contact angle () and contact radius (R) of ethanol-water mixture drop are recorded with time. With excess ethanol, the drop evaporation is principally controlled by a phase in which both the contact angle and contact radius are falling. A diffusional model assuming linear relation between contact radius and time is proposed as = eR 3 + cR 1, where e and c denote fitting coefficients. This model correlates with the experimental data.
8. The experimental results, from micro-Particle Image Velocimetry (µPIV), of the spatial and temporal velocity field within pure water and ethanol-water mixture droplets evaporating on a glass substrate are reported. The drop profile, evaporation rate and surface temperature were also measured. For pure water droplets, the redial velocity is found to exhibit a maximum spatially towards the three-phase contact line and to increase dramatically towards the end of the drop lifetime. For ethanol-water droplets, three flow phases were observed. (I) vortical flow where concentration differences arises during the preferential evaporation of ethanol. (II) transient flow which is possibly due to ethanol depletion at the apex of the drop leading to a surface tension instability and (III) characterized by radial flow towards the contact line, matching the evaporative flux and identical to the flow measured for pure water.
9. Evaporation phase change processes of water/methanol mixtures nanostructured surfaces which has an has an array of high-aspect-ratio nanowires (height/diameter ~ 125) and which possesses superhydrophobicity (>140°) and low contact angle hysteresis (1.2–2.1°), allowing the liquid droplets to remain in the 'fakir' state throughout the evaporation processes. Sessile droplets of deionized (DI) water and water/methanol binary mixture test liquids with their contact angles and base diameters are monitored. The results show that the nanostructures play a critical role in the droplet dynamics during evaporation.
10. Analysis of the effects of evaporative cooling on the evaporation of liquid droplets using a combined field approach gives the influences of the evaporative cooling on the evaporation of pinned sessile droplets and its predictions are found in good agreement with the previous theoretical and experimental results. An evaporative cooling number Ec can evaluate the strength of the evaporative cooling. Therefore, the results show that both the evaporation flux along the droplet surface and the total evaporation rate of the droplet decrease as the evaporative cooling number Ec increases.For drying droplets, there exists a critical valueEcCrit below which the evaporative cooling effect can be neglected and above which the significance of the effect increases. The present work may also have more general applications to coupled field problems in which all the fields have the same governing equation.
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