Mona Morovat; Omid Bakhtiari
Abstract
Ability and compatibility of the membrane processes for gas separation are evaluated by their membranes’ permeability and selectivity where both have been tried to enhance in promising membrane generation of mixed matrix membranes (MMMs). In the current study, two- and three-dimensional models ...
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Ability and compatibility of the membrane processes for gas separation are evaluated by their membranes’ permeability and selectivity where both have been tried to enhance in promising membrane generation of mixed matrix membranes (MMMs). In the current study, two- and three-dimensional models were constructed for MMMs, and the Fick's first law was solved numerically in them by using the Finite Element Method (FEM) and Computational Fluid Dynamic (CFD) tools. The effects of different MMMs structural parameters such as the volume fraction, size and mode of packing, i.e., regular or random, of the filler particles were investigated on the effective permeability of the pure gaseous penetrants through the MMMs. Furthermore, the interfacial equilibrium constant of the penetrants and their diffusivity ratios were also evaluated in view point of their impacts on the MMMs’ separation performance. Some well-known established models including Maxwell, Bruggeman, Lewis - Nielsen, Pal, and Chiew - Glandt were applied in the modeling. Deviation of the simulation results from the experimentally measured ones were low enough, however, at higher loadings of the filler particles the simulation deviation became greater. Simulated results through PSF - MCM-41 MMMs were compared with those of experimentally measured ones and AAREs of 31.0 (The lowest deviation), 42.7, and 41.0 % obtained for CO2, O2, and N2, respectively.
Modeling and Simulation
N. Hajilary; S. Hashemi; M. Hajiabadi
Abstract
MXene membranes perform well in biofuel separation due to their excellent hydrophilicity, flexibility, and mechanical strength. For the first time, computational fluid dynamics was used to model the dehydration of ethanol through the pervaporation system by the MXene membrane. We discretized the momentum ...
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MXene membranes perform well in biofuel separation due to their excellent hydrophilicity, flexibility, and mechanical strength. For the first time, computational fluid dynamics was used to model the dehydration of ethanol through the pervaporation system by the MXene membrane. We discretized the momentum and continuity equations using finite element methods and predicted the mass transport. Experimental results and model data were in good agreement (less than 10 %). The feed velocity, feed concentration, and membrane thickness all had positive effects on the separation factors while the temperature had a decreasing effect. This model's efficiency has decreased by 35 % after increasing the feed flow rate by 10 times. In addition, the separation factor increases tenfold when temperature is raised from 25 to 70 °C.
Transport Phenomena,
Hossein Hadi Najafabadi; Mostafa Keshavarz Moraveji
Volume 13, Issue 4 , November 2016, , Pages 46-61
Abstract
In this paper, three-dimensional incompressible laminar fluid flow in a rectangular microchannel heat sink (MCHS) using Al2O3/water nanofluid as a cooling fluid is numerically studied. CFD prediction of fluid flow and forced convection heat transfer properties of nanofluid using single-phase and two-phase ...
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In this paper, three-dimensional incompressible laminar fluid flow in a rectangular microchannel heat sink (MCHS) using Al2O3/water nanofluid as a cooling fluid is numerically studied. CFD prediction of fluid flow and forced convection heat transfer properties of nanofluid using single-phase and two-phase model (Eulerian-Eulerian approach) are compared. Hydraulic and thermal performance of microchannels are investigated according to the results of the friction factor, pumping power, average heat transfer coefficient, thermal resistance, average temperature of the walls and entropy generation. In addition, due to the CFD results, two correlations for predication of Nusselt number and friction factor are presented. Comparing the predicted Nusselt number using single-phase and two-phase models with experimental data shows that the two-phase model is more accurate than single-phase model. The results show that increasing the volume fraction of nanoparticles leads to increases the heat transfer coefficient and reduces the heat sink wall temperature, but it leads to the undesirable effect of increase in pumping power and total entropy generation.
Transport Phenomena,
M. Keshavarz Moraveji*; E. Ghaderi
Volume 12, Issue 2 , April 2015, , Pages 75-87
Abstract
The effective parameters on Ohmic heating in static system containing biosolid-water were studied. The effects of distribution of particles, salinity and electric field strength on electrical conductivity, profiles of temperature, heat generation have been investigated. The experimental data verification ...
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The effective parameters on Ohmic heating in static system containing biosolid-water were studied. The effects of distribution of particles, salinity and electric field strength on electrical conductivity, profiles of temperature, heat generation have been investigated. The experimental data verification with simulation results using computational fluid dynamics (CFD) method were carried out. Governing equations (heat transfer and electrical equations) were discretized with finite element method. The experimental data and CFD results showed that in Ohmic heating process, the current diffusion in all the products is faster than traditional methods and the diffusion rates are equal for both biosolid-liquid phases.
Modeling and Simulation
Volume 6, Issue 4 , October 2009, , Pages 34-44
Abstract
This paper reports the result of CFD simulation of catalytic oxidation of benzene on monolithic catalyst. The geometries ofthe catalyst and reactor were designed in Gambit software and simulation of catalytic oxidation was carried out in fluent 6.2. Results of simulation showed excellent agreement with ...
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This paper reports the result of CFD simulation of catalytic oxidation of benzene on monolithic catalyst. The geometries ofthe catalyst and reactor were designed in Gambit software and simulation of catalytic oxidation was carried out in fluent 6.2. Results of simulation showed excellent agreement with the experimental data. This study confirmed the accuracy of the used model in this simulation (Mars van Krevelen). Furthermore, CFD made it possible to obtain a more accurate view ofheat transfer and fluid flow. This study confirmed CFD is the best tool for study offluid regime and heat transfer and especially, concentration of species, and surface deposition along the reactor in the chemical process.
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 26-45
Abstract
ewline"> Dispersion of heavy gases is considered to be more hazardous than the passive ones because it takes place more slowly. When the gas is accidentally released at ground level or where there are many obstacles in the area it is considered to be a heavy gas. In this paper, based on the extensive ...
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ewline"> Dispersion of heavy gases is considered to be more hazardous than the passive ones because it takes place more slowly. When the gas is accidentally released at ground level or where there are many obstacles in the area it is considered to be a heavy gas. In this paper, based on the extensive experimental work of McQuid and Hanna, the model was tested against two types of experiments: A simple experiment “Thorney Island” and a complex experiment “Kit Fox” in order to validate CFD code. In order to accomplish this validation the multiphase approach was employed. Also, the vertical temperature gradient in the atmosphere was investigated. The investigation of wind speed was done taking factors such as time, height and direction into consideration. In order to reduce the number of elements in the computational domain, a combination of 2D and 3D geometry was utilized. The results showed that the wind inlet correction, as well as the temperature gradient, had a significant influence on gas concentration records.
Modeling and Simulation
Volume 5, Issue 4 , October 2008, , Pages 12-22
Abstract
The turbulent flow field generated in a baffled stirred tank was computed by large eddy simulation (LED) and the flow field was developed using the Sliding Mesh (SM) approach. In this CFD study, mixing times and power number have been determined for a vessel agitated by a 6-blade Rushton turbine. The ...
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The turbulent flow field generated in a baffled stirred tank was computed by large eddy simulation (LED) and the flow field was developed using the Sliding Mesh (SM) approach. In this CFD study, mixing times and power number have been determined for a vessel agitated by a 6-blade Rushton turbine. The predicted results were compared with the published experimental data. The satisfactory results of comparisons indicate the potential usefulness of this approach as a computational tool for designing stirred reactors.