Ammar Abdulaziz Alsairafi

Kuwait University, Al Kuwayt, Al Asimah Governorate, Kuwait

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Publications (30)25.22 Total impact

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    ABSTRACT: The effects of 24 kHz and 1.7 MHz ultrasonic waves on heat transfer from a thin platinum wire are investigated. The results revealed that the 1.7 MHz ultrasound waves could increase the heat transfer rate more efficiently than the lower frequency one. The CFD modeling of ultrasonication was performed to compare heat transfer, predict fluid flow patterns. The CFD results were validated by the experimental results with an excellent agreement.
    Heat and Mass Transfer 04/2014; · 0.84 Impact Factor
  • Masoud Rahimi, Neda Azimi, Fahime Parvizian, Ammar Abdulaziz Alsairafi
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    ABSTRACT: This paper reports the results of CFD modeling for evaluating micromixing efficiency in presence of polymeric microparticles in a continuous tubular sonoreactor. The studied tubular sonoreactor was equipped with four 1.7 MHz ultrasound transducers and micromixing efficiency was analyzed using Villermaux/Dushman reaction. The main objective of this study is to illustrate the simultaneous effects of 1.7 MHz ultrasound waves and polymeric microparticles on micromixing performance from the fluid dynamics point of view. In order to model the presence of these microparticles, the Eulerian multiphase model was applied based on kinetic theory of granular flow. The dynamic mesh method was used to model the vibration of 1.7 MHz piezoelectric transducers. CFD modeling results indicate the positive effects of the presence of microparticles on micromixing efficiency and more efficient velocity distribution inside the sonoreactor. This was interpreted as the ability of high frequency ultrasound waves (1.7 MHz) to move and disperse the microparticles.
    Computers & Chemical Engineering 01/2014; 60:403–412. · 2.09 Impact Factor
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    Fahime Parvizian, Masoud Rahimi, Neda Azimi, Ammar A. Alsairafi
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    ABSTRACT: The effect of high-frequency (1.7 MHz) ultrasound waves on the mixing rate in a new continuous tubular sonoreactor was investigated by CFD modeling. Modeling of piezoelectric transducer (PZT) vibrations was done based on the dynamic mesh model. Results indicate that the acoustic streams were in the direction of wave propagation and their maximum velocity near the PZT surface agreed well with experimental measurements. The micromixing efficiency of the sonoreactor was studied by adopting the Villermaux/Dushman reaction in the modeling. Comparison of the calculated relative segregation index from modeling results with experimental data revealed reasonable accordance.
    Chemical Engineering & Technology 01/2014; 37(1). · 1.37 Impact Factor
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    ABSTRACT: Graphical abstract A schematic diagram of the experimental setup.
    Energy Conversion and Management 01/2014; 83:48–57. · 3.59 Impact Factor
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    ABSTRACT: An experimental and modeling investigation of catalytic reforming of naphtha in a pilot-scale packed bed reactor is described in the present work. The effects of operating conditions on the reactor products were studied utilizing statistical method. A kinetic model including three pseudo species and eight light components was proposed and the coefficients of reaction rate equations were obtained. Good agreement was achieved between the proposed model results and the experimental measurements. Different regions of the reactor with different growth rate of pseudo species and light components were detected by analyzing concentration profiles along the reactor. It was concluded that the precision of the developed kinetic model make it suitable for implementing in a reactor model to predict the analysis of products of an industrial catalytic reforming unit. This is crucial for optimum operation of the industrial unit and its downstream processes, including steam reforming and hydrocracking units which uses light component streams of catalytic reforming process as feed stock or part of their inputs streams. Also, the achieved results about the effects of different operating conditions on the reactor productivity, may offer several clues for improvement of control philosophy, startup and shutdown procedure of this process.
    Journal of the Taiwan Institute of Chemical Engineers 01/2013; · 2.08 Impact Factor
  • Mahdieh Abolhasani, Masoud Rahimi, Maryam Dehbani, Ammar Abdulaziz Alsairafi
    Numerical Heat Transfer Applications 11/2012; 62(10):822-841. · 1.85 Impact Factor
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    mahdieh abolhasani, masoud rahimi, maryam dehbani, ammar abdulaziz alsairafi
    The 4rd National ConferenceonCFD Applications in Chemical & PetroleumIndustries; 05/2012
  • Mohammad Davood Ahanj, Masoud Rahimi, Ammar Abdulaziz Alsairafi
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    ABSTRACT: This paper reports experimental and Computational Fluid Dynamics (CFD) studies on combustion and radiation heat transfer from a real radiant tube heater. The temperature along the radiant tube as well as at different positions in a test room has been measured. A good agreement between the experimental and predicted results has been found. Based on this validation, the effect of excess air, presented by Air Factor (AF) on efficiency of heater has been studied, theoretically. Moreover, the effect of inlet air preheating on heater efficiency has been examined. The results show that the higher values of excess air can reduce the heater efficiency. The air preheating temperature caused positive effect on heater efficiency. In addition, the results show at higher preheating temperature the effect of AF value on heater efficiency is negligible.
    International Communications in Heat and Mass Transfer 03/2012; 39(3):432–438. · 2.21 Impact Factor
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    ABSTRACT: Two different modeling methods have been proposed to relate the Peng-Robinson-Stryjek-Vera (PRSV) parameter, κ 1, 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.
    Korean Journal of Chemical Engineering. 01/2012; 29(5):657-667.
  • Abbas Khoshhal, Masoud Rahimi, Ammar Abdulaziz Alsairafi
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    ABSTRACT: CFD modeling of NOx emission via N2O-intermediate mechanism was developed to predict the NOx formation in an experimental furnace equipped with high temperature air combustion (HiTAC) system. The good agreement between the predicted and measured results illustrates the superiority of using a N2O-intermediate model in prediction of NOx emission during low peak temperature, which happens in HiTAC systems. Moreover, the CFD and measured results show that the flame volume as well as NOx emission significantly depends on temperature and oxygen concentration. Lower NOx emission was experimentally and numerically obtained at lower input oxygen concentration conditions.
    Numerical Heat Transfer Applications 04/2011; Part A: Applications(Vol. 59):633-651. · 1.85 Impact Factor
  • Masoud Rahimi, Saeideh Amraei, Ammar Abdulaziz Alsairafi
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    ABSTRACT: 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. Key wordsCFD–Visco-jet–Mixing–Modeling Viscous Fluid
    Korean Journal of Chemical Engineering 01/2011; 28(6):1372-1379. · 1.06 Impact Factor
  • Abhas Khoshhal, Masoud Rahimi, Afshar Ghahramani, Ammar Abdulaziz Alsairafi
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    ABSTRACT: 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. Key wordsCFD–HiTAC–HRSG Boiler–Modeling–Heat Transfer
    Korean Journal of Chemical Engineering 01/2011; 28(5):1181-1187. · 1.06 Impact Factor
  • A. Parvareh, M. Rahimi, S. S. Madaeni, A. A. Alsairafi
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    ABSTRACT: This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale. For this purpose, a dead-end membrane cell equipped with a marine type impeller was used. The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux. Consequently, permeate fluxes were measured at various impeller rotational speeds. The computational fluid dynamics (CFD) predicted dynamic pressure was related to the fluxes obtained in the experiments. Using the CFD modeling, it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.
    Chinese Journal of Chemical Engineering - CHINESE J CHEM ENG. 01/2011; 19(1):18-25.
  • Abbas Khoshhal, Masoud Rahimi, Ammar Abdulaziz Alsairafi
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    ABSTRACT: The influence of the fuel temperature on NOx formation was investigated numerically. For this purpose CFD modeling of NOx emission in an experimental furnace equipped with high temperature air combustion (HiTAC) system was studied. The comparison between the predicted results and measured values have shown good agreement, which implies that the adopted combustion and NOx formation models are suitable for predicting the characteristics of the flow, combustion, heat transfer, and NOx emissions in the HiTAC chamber. Moreover the predicted results show that increase of the fuel temperature results in a higher fluid velocity, better fuel jet mixing with the combustion air, smaller flame and lower NOx emission.
    International Communications in Heat and Mass Transfer - INT COMMUN HEAT MASS TRANS. 01/2011; 38(10):1421-1427.
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    ABSTRACT: This paper reports the experimental and Computational Fluid Dynamics (CFD) modeling studies on heat transfer, friction factor and thermal performance of an air cooled heat exchanger equipped with three types of tube insert including butterfly, classic and jagged twisted tape. In the studied range of Reynolds number the maximum thermal performance factor was obtained by the butterfly insert with an inclined angle of 90°. The results have also revealed that the difference between the heat transfer rates obtained from employing the classic and jagged inserts reduces by decreasing the twist ratio. The CFD predicted results were used to explain the observed results in terms of turbulence intensity. In addition, good agreements between the predicted and measured Nu number as well as friction factor values were obtained.
    International Communications in Heat and Mass Transfer 01/2011; 38(3):383-390. · 2.21 Impact Factor
  • Abbas Khoshhal, Masoud Rahimi, Ammar Abdulaziz Alsairafi
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    ABSTRACT: NOx emission, heat transfer, and high temperature air combustion (HiTAC) in a boiler of Mobin Petrochemical Complex, Iran was numerically studied. The comparison between the measured values and the CFD predicted results showed good agreement, which implied that the adopted combustion and NOx formation models are suitable for correctly predicting characteristics of the heat recovery steam generation (HRSG) boiler. The predicted results show that NOx emission within the boiler depends highly on temperature, as well as oxygen concentration. Moreover, the influence of the equivalence ratio at a fixed air mass flow rate on the flame temperature and NOx formation has been investigated.
    Numerical Heat Transfer Applications 08/2010; Part A: Applications(Vol. 58):295-312. · 1.85 Impact Factor
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    ABSTRACT: In the present study, different two-phase flow regimes in horizontal and vertical tubes have been studied experimentally and theoretically. A 3-D Computational Fluid Dynamics (CFD) modeling was carried out in order to model gas–liquid two-phase flow using volume of fluid (VOF) model. An Electrical Resistance Tomography (ERT) system was used to visualize these flow regimes, which were produced by change in the gas to liquid flow rate ratio. The reconstructed images from the ERT measurement and corresponding captured photographs for different flow regimes have been compared with the CFD predictions and a good qualitative agreement was observed between them.
    International Communications in Heat and Mass Transfer - INT COMMUN HEAT MASS TRANS. 01/2010; 37(3):304-311.
  • M. Rahimi, B. Aghel, A. A. Alsairafi
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    ABSTRACT: In this paper a study on the role of wire coils inserted in the oxygen supply channels of a proton exchange membrane fuel cell (PEMFC) is reported. Different power densities have been obtained at different oxygen flow rates with and without insert. The experimental results clearly reveal that inserting a wire coil can increase the generated power density up to 41% in some layouts. The CFD modeling is carried out to explain and to analyze the observed results. The generated circumferential flow close to the gas diffusion layer (GDL) is found to be the main reason for the obtained experimental results.
    Chemical Engineering and Processing - CHEM ENG PROCESS. 01/2010; 49(7):689-696.
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    Asghar Alizadehdakhel, Masoud Rahimi, Ammar Abdulaziz Alsairafi
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    ABSTRACT: In the present study a gas/liquid two-phase flow and the simultaneous evaporation and condensation phenomena in a thermosyphon was modeled. The volume of fluid (VOF) technique was used to model the interaction between these phases. Experiments in a thermosyphon were carried out at different operating conditions. The CFD predicted temperature profile in the thermosyphon was compared with experimental measurements and a good agreement was observed. It was concluded that CFD is a useful tool to model and explain the complex flow and heat transfer in a thermosyphon.
    International Communications in Heat and Mass Transfer - INT COMMUN HEAT MASS TRANS. 01/2010; 37(3):312-318.
  • Masoud Rahimi, Aso Kakekhani, Ammar Abdulaziz Alsairafi
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    ABSTRACT: 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 CFD-predicted 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. Key wordsCFD-Helical Ribbon-Hydrodynamics-Mixing-Visualization Mathematical Modeling
    Korean Journal of Chemical Engineering 01/2010; 27(4):1150-1158. · 1.06 Impact Factor