Full article
A. Mohammadi; J. Moghaddas
Volume 16, Issue 3 , Summer 2019, Pages 3-22
Abstract
Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on ...
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Although not listed on the United States Pharmacopeia (USP), like standard USP 2, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on a tablet containing trace amounts of the active pharmaceutical ingredient. In this work, firstly, small volume USP 2 apparatus was designed and manufactured using downscaling rules and considering standard USP 2 as a reference. Then, velocity profile, flow patterns, and shear rate were obtained by PIV and COMSOL simulation software at paddle speeds of 66 and 133 rpm, corresponding to agitation speed of 50 and 100 rpm, respectively, in the standard USP 2. Comparison between experimental and computational results showed acceptable adaptation. Instantaneous velocity data showed eddies and secondary flows in different zones of the vessel, which is desirable for micro-mixing but undesirable in terms of system consistency and reproducibility, as sampling from these zones are known to lead to inconsistent data. Furthermore, increased agitation rate led to the disappearance of rotational zones around the paddle. The magnitude of velocity and shear rate increased by 35% with an increment of paddle stirring from 66 to 133 rpm.
Full article
M.E zeynali; H. Abedini; H. R. Sadri
Volume 16, Issue 3 , Summer 2019, Pages 23-36
Abstract
Divinylbenzene (DVB) is produced by catalytic dehydrogenation of DEB at high temperature and atmospheric pressure. Ethylvinylbenzene (EVB) is produced as a useful chemical during dehydrogenation of DEB. Also some other liquid and gaseous by products is produced during dehydrogenation. A set-up has been ...
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Divinylbenzene (DVB) is produced by catalytic dehydrogenation of DEB at high temperature and atmospheric pressure. Ethylvinylbenzene (EVB) is produced as a useful chemical during dehydrogenation of DEB. Also some other liquid and gaseous by products is produced during dehydrogenation. A set-up has been developed to conduct the DEB dehydrogenation reactions experiments to prepare DVB at different conditions. Model equations for DEB dehydrogenation reactor have been solved by genetic algorithm (GA) method using MATLAB software. Reaction rate constants and absorption coefficients were determined at various temperatures. The conversion of DEB and ethylvinyl benzene (EVB) in the reactor was predicted by mathematical modeling and compared with experimental results. The comparison shows good agreements between experimental and modeling results. The combined effects of DEB flow rate and catalyst weight as time factor were investigated on conversion of DEB and production of EVB and DVB. Effects of temperature on consumption of DEB and production of EVB and DVB in the tubular reactor were investigated.
Full article
M. r. Talaghat; F. Shafiei
Volume 16, Issue 3 , Summer 2019, Pages 37-57
Abstract
The main objective of this research is to analyze optimization and the thermal performance of circular porous fins with four different profiles, rectangular, convex, triangular and concave under fully wet conditions. In this research, a linear model was used for the relationship between humidity and ...
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The main objective of this research is to analyze optimization and the thermal performance of circular porous fins with four different profiles, rectangular, convex, triangular and concave under fully wet conditions. In this research, a linear model was used for the relationship between humidity and temperature. Also, modeling is assumed one-dimensional and the temperature changes only in the direction of the radius of the fin. Moreover, the thermal conductivity and heat transfer coefficient are a function of porosity and temperature, respectively. The governing equations are solved using the Galerkin method and the finite difference method and the use of the Gauss-Seidel algorithm. In this study, the effect of different parameters including relative humidity, Darcy number and Rayleigh number and porosity on temperature distribution, fin efficiency, and fin effectiveness was investigated. The results showed that the efficiency, effectiveness, and heat transfer rate to the base for the rectangular profile is higher than other profiles. In this research, the Nelder-Mead algorithm is used for optimization. The results showed that to maintain optimal conditions, the ratio of thickness to fin length should be increased by increasing relative humidity or decreasing the Darcy number, Rayleigh number and porosity.
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A. Ranjbara; F. Aghamiri; A. Irankhah
Volume 16, Issue 3 , Summer 2019, Pages 58-69
Abstract
In this research effect of synthesis method of magnesium aluminate as support of Ni catalysts at the reverse water gas shift (RWGS) reaction was evaluated. The RWGS reaction is applied in Carbon Dioxide Hydrogenation to Form Methanol via a Reverse Water-Gas Shift Reaction (CAMERE) process for the transformation ...
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In this research effect of synthesis method of magnesium aluminate as support of Ni catalysts at the reverse water gas shift (RWGS) reaction was evaluated. The RWGS reaction is applied in Carbon Dioxide Hydrogenation to Form Methanol via a Reverse Water-Gas Shift Reaction (CAMERE) process for the transformation of CO2 into methanol. The MgAl2O4 supports were prepared by sol-gel (M1), surfactant-assisted co-precipitation (M2) and ultrasonic-assisted co-precipitation (M3) techniques. 1.5wt.% Ni/M1 showed highest CO2 conversion (42.1%) and lowest CO selectivity, while 1.5wt.% Ni/M2 showed the lowest CO2 conversion and the highest CO selectivity (>92.5 %). The 1.5wt.% Ni/M3 showed similar catalytic activity as 1.5 wt.%Ni/M2, but with lower CO selectivity. The high CO selectivity of 1.5 wt.% Ni/M2 with a BET surface area of 121.7 m2g-1 was accredited to a higher dispersion of Ni particles resulted by higher total pore volume of this catalyst. High specific surface area along with large total pore volume, is effective in increasing the nickel dispersity. The following pore size distribution and total pore volume order was obtained for catalysts: 1.5wt.% Ni/M2> 1.5wt.% Ni/M3> 1.5wt.% Ni/M1. Among the prepared supports, M1 with BET of 174.5 m2.g-1 showed the highest specific surface area. All prepared supports and catalysts possessed mesoporous structure. Well dispersed NiO species with high interaction with the support were detected by TPR analysis. The SEM images detected particles with less than 80 nm for M2 and 1.5wt.%Ni/M2 samples. The long term stability test performed on 1.5wt.%Ni/M2 showed great catalytic activity after 15h on stream.
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S. Salimi; R. Beigzadeh
Volume 16, Issue 3 , Summer 2019, Pages 70-83
Abstract
In the study, the thermal-hydraulic performance of the zigzag channels with circular cross-section was analyzed by Computational Fluid Dynamics (CFD). The standard K-Ꜫ turbulent scalable wall functions were used for modeling. The wall temperature was assumed constant 353 K and water was used as the ...
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In the study, the thermal-hydraulic performance of the zigzag channels with circular cross-section was analyzed by Computational Fluid Dynamics (CFD). The standard K-Ꜫ turbulent scalable wall functions were used for modeling. The wall temperature was assumed constant 353 K and water was used as the working fluid. The zigzag serpentine channels with bend angles of 5 - 45° were studied for turbulent flow from 4000 to 40,000 Reynolds number (Re). The thermal performance of the zigzag 45° channel was better than the other channels and also it had the highest friction factor (f). The bends caused secondary flow, and as the bend angle increased, the secondary flow increased. This Phenomenon had a positive effect on thermal performance and a negative effect on hydraulic performance by increasing the friction factor. The obtained CFD data used to develop correlations for predicting the Nu and f as the functions of Re and bend angles. The correlation constants were optimized by the genetic algorithm method which leads to the mean relative errors of 3.32% and 6.94% for Nu and f estimation, respectively.
Full article
M. Asadollahi
Volume 16, Issue 3 , Summer 2019, Pages 84-92
Abstract
Although two-phase flow is frequently encountered in various location of the process plants, there is no a general accepted and verified two-phase flow model that may be used to size lines for such conditions. An obvious example is condensate water return lines. The API method that used in this study ...
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Although two-phase flow is frequently encountered in various location of the process plants, there is no a general accepted and verified two-phase flow model that may be used to size lines for such conditions. An obvious example is condensate water return lines. The API method that used in this study is based on the homogeneous equilibrium flow assumption, that is, equal velocity and equal temperature in both liquid and vapor phases. Also, DIERS method has used to verify and clarify the HEM approach to calculate the pressure drop in two phase regimes. The objective of this study is to introduce a solution for process lines design during different flashing scenarios. In this work by applying API method we can find the two-phase line pressure drop and upstream pressure while by using DIERS method we would be able to realize that for a specified length of pipe how much two phase flow could pass through when the pressure drop is just same as the API model.