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Numerical and experimental investigation on a new modified valve in a valve tray column
Asghar Alizadehdakhel,Ammar Abdulaziz Alsairafi,Masoud Rahimi 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2
This paper reports experimental and computational fluid dynamics (CFD) modeling studies on the performance of three modified valves operating in a valve tray column. The original and modified valves including vnotched, warped and double-valve are tested experimentally. The experimental rig was a Perspex column having a single valve equipped with a fluctuating plate to measure the quality of gas distribution by using laser sensors. Two-stage nested designs were employed to show the repeatability and consistency of the measurements. In the CFD modeling, the volume of fluid (VOF) method was used to model the gas-liquid two-phase flow inside the column. A good agreement was observed between experimental data and the CFD predictions. The results showed that the double-valve layout provides a better gas distribution, smaller bubbles with greater interface area and lower pressure drop in comparison with the original and the two other modified valves.
Masoud Rahimi,Aso Kakekhani,Ammar Abdulaziz Alsairafi 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.4
Experimental and computational fluid dynamic (CFD) modeling studies have been performed on mixing characteristics of a new modified helical ribbon impeller in a viscous medium. A novel arrangement for the multiple reference frame (MRF) technique was proposed and the modeling results were compared with those of conventional MRF selecting method. Calculations were performed to study the effects of several parameters: axial flow number,axial circulation time, impeller clearance, and power consumption. The higher performance of the modified impeller has been proven in terms of axial flow number and axial circulation time. The results showed that significant improvement in mixing performance can be obtained at a higher impeller clearance with the modified impeller employed. In addition, the power consumption by the new impeller has been compared with that of the classic one. The CFDpredicted flow patterns generated by the impellers were used to explain the higher performance of the modified impeller. In addition, the results reveal that the CFD-predicted particle volume fractions at various axial distances from the tank bottom are reasonably in agreement with the experimental observations.
Experimental and computational fluid dynamics modeling of mixing by Visco-jet impellers
Masoud Rahimi,Saeideh Amraei,Ammar Abdulaziz Alsairafi 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.6
This paper reports experimental and computational frluid dynamics (CFD) studies on an impeller called Visco-jet with the aim of finding the effect of two side diameters ratio of its blade, which has a semi-conical shape,on drawdown process of floating polymericparticles into high viscosity glycerin solution. Nine different geometries were examined experimentally, and there were significant differences in their performance. The results reveal that when diameter of smaller side of semi-cone impeller is half of the other side, mixing was performed in a more efficient way. The CFD-predicted results have been used for explaining the experimental observation. The CFD-predicted hydrodynamics parameters confirm superiority of this geometry compared with the other ones.
Abhas Khoshhal,Masoud Rahimi,Afshar Ghahramani,Ammar Abdulaziz Alsairafi 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5
This paper reports a numerical study on the possibility of using high temperature air combustion (HiTAC)technique in the heat recovery steam generator (HRSG) boiler of the Fajr Petrochemical Complex, Iran. For this purpose a theoretical fuel nozzle which operates in HiTAC mode of combustion has been installed and modeled using the computational fluid dynamics (CFD) technique. By aim of establishing an efficient heat transfer rate to the boiler’s tubes, the proper nozzle location and an optimum mass flow rate of fuel have been found. The results show that by using this modification it is possible to increase the steam temperature up to 37 percent.
Tahmaseb Hatami,Masoud Rahimi,Hiua Daraei,Ehsan Heidaryan,Ammar Abdulaziz Alsairafi 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.5
Two different modeling methods have been proposed to relate the Peng-Robinson-Stryjek-Vera (PRSV)parameter, κ1, to some common thermodynamic constants, including critical temperature (Tc), critical pressure (Pc),acentric factor (ω) and molecular weight (Mw). The methods are artificial neural network (ANN) and adaptive networkbased fuzzy inference System (ANFIS). A set of 159 data points (116, 23 and 20) was used for construct training, validating and testing, respectively. The radius parameter of ANFIS was determined through genetic algorithm (GA) optimization technique. The ANN and especially ANFIS results are in a good agreement with most of the compound groups.
Sayed Reza Shabanian,Masoud Rahimi,Amin Amiri,Shahram Sharifnia,Ammar Abdulaziz Alsairafi,정재학,김우경 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.11
A numerical model was developed and validated to simulate and improve the reforming efficiency of methane to syngas (CO+H2) in an autothermal reactor. This work was undertaken in a 0.8 cm diameter and 30 cm length quartz tubular reactor. The exhaust gas from combustion at the bottom of reactor was passed over a Ru/γ-Al2O3 catalyst bed. The Eddy Dissipation Concept (EDC) model for turbulence-chemistry interaction in combination with a modified standard k-ε model for turbulence and a reaction mechanism with 23 species and 39 elementary reactions were considered in the combustion model. The pre-exponential factors and activation energy values for the catalyst (Ru) were obtained by using the experimental results. The percentage of difference between the predicted and measured mole fractions of the major species in the exhaust gas from combustion and catalyst bed zones was less than 5.02% and 7.73%,respectively. In addition, the results showed that the reforming efficiency, based on hydrogen yield, was increased with increase in catalyst bed’s thermal conductivity. Moreover, an enhancement of 4.34% in the reforming efficiency was obtained with increase in the catalyst bed wall heat flux from 0.5 to 2.0 kW/m2.