Ammar Abdulaziz Alsairafi

Kuwait University, Al Kuwayt, Al Asimah, Kuwait

Are you Ammar Abdulaziz Alsairafi?

Claim your profile

Publications (35)63.78 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Five asymmetrical shaped microchannels were used to investigate the effect of channel confluence angle, flow rate and flow rate ratio on the mixing performance in a passive mixing test. The flow characteristics for all geometries were studied experimentally and numerically using CFD technique. The results reveal that the mixing performance depends on the channel geometry, total flow rate and inlet flow rate ratios. The classical T-shape microchannel had the worst performance in the lower flow rate and in higher Re numbers its performance was placed between the other ones. Furthermore, the mixing effectiveness for all microchannels was defined and measured at various feed flow rates. The results indicate that the mixing effectiveness increases with increasing flow rate ratio and decrease of confluence angle. The reasons for the observed experimental results were analyzed by the predicted CFD flow patterns.
    Computers & Chemical Engineering 12/2014; 73. DOI:10.1016/j.compchemeng.2014.12.007 · 2.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study aims to join up wind and solar energy as the renewable energy sources for more efficient production of electrical energy. A laboratory-scale cooling device based on a conic wind-collecting tunnel was designed and then fabricated to cool down a photovoltaic (PV) cell. The collected wind from conic tunnel was employed with two goals; first, it was considered as a coolant fluid for PV cell. Second, it was applied for producing electrical energy via a designed turbine. The great potential of the proposed cooling device on the performance of the PV cell are the focus of this study. The obtained results reveals that the total output power was increased 36% from both the PV cell and turbine electrical energy production. In order to explain the observed results, a CFD modeling based on MRF technique were undertaken. The flow distributions in two modes (with and without turbine) were compared and the effect of turbine blade was then interpreted in terms of air flow pattern diverted to underneath of the studied PV cell.
    Energy Conversion and Management 07/2014; 83:48–57. DOI:10.1016/j.enconman.2014.03.053 · 3.59 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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; 50(9). DOI:10.1007/s00231-014-1346-9 · 0.93 Impact Factor
  • Masoud Rahimi, Neda Azimi, Fahime Parvizian, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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. DOI:10.1016/j.compchemeng.2013.09.006 · 2.45 Impact Factor
  • Fahime Parvizian, Masoud Rahimi, Neda Azimi, Ammar A. Alsairafi
    [Show abstract] [Hide abstract]
    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):113–122. · 2.18 Impact Factor
  • Source
    Fahime Parvizian, Masoud Rahimi, Neda Azimi, Ammar A. Alsairafi
    [Show abstract] [Hide abstract]
    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). DOI:10.1002/ceat.201300231 · 2.18 Impact Factor
  • Mahbube Faryadi, Mona Akbari, Masoud Rahimi, Ammar Abdulaziz Alsairafi
    5th CFD conference, Tehran, Iran University of Science and Technology; 05/2013
  • Ammar A. Alsairafi
    [Show abstract] [Hide abstract]
    ABSTRACT: SUMMARY This paper provides a theoretical study of the effects of ambient conditions on the thermodynamic performance of a hybrid combined-nuclear cycle power plant. The operational parameters investigated are based on the first and second laws of thermodynamics, which include the ambient air temperature and ambient relative humidity (Φ). The results obtained for the gas turbine model are shown to agree very well with operational data from the Al-Zour Emergency power plant in Kuwait. The ambient temperature was studied within the range of 0–55 °C. The analysis shows that the ambient air temperature has strong effects on plant performance and that operating the system at a high temperature will degrade the performance. Power output is reduced when the temperature is above the standard ambient temperature of 15 °C, and this loss rate is about 17% at 55 °C. The effect of ambient relative humidity (Φ) becomes significant only at higher temperatures. The ambient temperature has a large effect on the exergy destruction of the heat recovery steam generator exhaust, but it has little effect on other components of the plant. The analysis also indicates that reducing the temperature from 55 to 15 °C could help decrease the total exergy destruction of the plant by only 2%. Copyright © 2011 John Wiley & Sons, Ltd.
    International Journal of Energy Research 03/2013; 37(3). DOI:10.1002/er.1901 · 2.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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; 45(4). DOI:10.1016/j.jtice.2013.11.001 · 2.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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-ɛ 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.
    Korean Journal of Chemical Engineering 11/2012; 29(11). DOI:10.1007/s11814-012-0030-3 · 1.24 Impact Factor
  • Mahdieh Abolhasani, Masoud Rahimi, Maryam Dehbani, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    ABSTRACT: This article reports the results of numerical study on the effect of high frequency ultrasounic waves on heat transfer rate. A cylindrical heater surrounded by water was exposed to a 1.7MHz piezoelectric transducer, and its temperature was measured with and without employing the ultrasound vibrations. Heat transfer rate enhancement values at various inputted heat fluxes were found, and augmentations up to 100% were obtained during sonication. The CFD modeling of ultrasound wave propagation was carried out to predict the fluid flow pattern and heat transfer inside the water. The CFD predicted results were in good agreement with the observed results.
    Numerical Heat Transfer Applications 11/2012; 62(10):822-841. DOI:10.1080/10407782.2012.712432 · 1.85 Impact Factor
  • Ammar A. Alsairafi
    [Show abstract] [Hide abstract]
    ABSTRACT: Combined‐cycle power plants are currently preferred for new power generation plants worldwide. The performance of gas‐turbine engines can be enhanced at constant turbine inlet temperatures with the addition of a bottoming waste‐heat recovery cycle. This paper presents a study on the energy and exergy analysis of a novel hybrid Combined‐Nuclear Power Plant (HCNPP). It is thus interesting to evaluate the possibility of integrating the gas turbine with nuclear power plant of such a system, utilizing virtually free heat. The integration arrangement of the AP600 NPP steam cycle with gas turbines from basic thermodynamic considerations will be described. The AP600 steam cycle modifications to combine with the gas turbines can be applied to other types of NPP. A simple modeling of Alstom gas turbines cycle, one of the major combined‐cycle steam turbines manufacturers, hybridized with a nuclear power plant from energetic and exergetic viewpoint is provided. The Heat Recovery Steam Generator (HRSG) has single steam pressure without reheat, one superheater and one economizer. The thermodynamic parameters of the working fluids of both the gas and the steam turbines cycles are analyzed by modeling the thermodynamic cycle using the Engineering Equation Solver (EES) software. In case of hybridizing, the existing Alstom gas turbine with a pressurized water nuclear power plants using the newly proposed novel solution, we can increase the electricity output and efficiency significantly. If we convert a traditional combined cycle to HCNPP unit, we can achieve about 20% increase in electricity output. This figure emphasizes the significance of restructuring our power plant technology and exploring a wider variety of HCNPP solutions. Copyright © 2011 John Wiley & Sons, Ltd.
    International Journal of Energy Research 06/2012; 36(8). DOI:10.1002/er.1841 · 2.74 Impact Factor
  • Source
    mahdieh abolhasani, masoud rahimi, maryam dehbani, ammar abdulaziz alsairafi
    The 4rd National ConferenceonCFD Applications in Chemical & PetroleumIndustries; 05/2012
  • [Show abstract] [Hide abstract]
    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.
    05/2012; 29(5-5):657-667. DOI:10.1007/s11814-011-0235-x
  • Mohammad Davood Ahanj, Masoud Rahimi, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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. DOI:10.1016/j.icheatmasstransfer.2012.01.011 · 2.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Boundary layer diffusion resistance in ion-exchange membrane increases the total system resistance and reduces the power output from electro dialysis process. In this research, the influence of ultrasound wave on diffusion boundary layer and electrochemical membrane properties for a cationic and an anionic exchange membrane is investigated. High frequency (1.7 MHz) piezoelectric transducers were used to induce ultrasound waves in the medium. Mixing was accomplished using a magnetic stirrer, ultrasonic and a combination of ultrasound and magnetic stirrer. The results showed that the membrane potential, transport number and selectivity were decreased with increase in electrolyte concentration in the anionic membrane. In cationic membrane, all mentioned properties were initially increased and then decreased with increase in the solution concentration. The SEM characterization of the membranes indicated that the cationic membrane has a smoother surface that led to its higher selectivity and membrane resistance compared with those of the anionic membrane. Moreover, In order to explain the observed experimental results, the CFD modeling technique has been used to illustrate flow pattern and acoustic streams propagation in the cell and shows when only the ultrasound transducer activated the established velocity near the membrane surface is twice that of stirrer activated case.
    Desalination 02/2012; 286:155–165. DOI:10.1016/j.desal.2011.11.016 · 3.96 Impact Factor
  • Abbas Khoshhal, Masoud Rahimi, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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 12/2011; 38(10):1421-1427. DOI:10.1016/j.icheatmasstransfer.2011.08.008 · 2.12 Impact Factor
  • Masoud Rahimi, Saeideh Amraei, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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 06/2011; 28(6):1372-1379. DOI:10.1007/s11814-010-0522-y · 1.24 Impact Factor
  • Abhas Khoshhal, Masoud Rahimi, Afshar Ghahramani, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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 05/2011; 28(5):1181-1187. DOI:10.1007/s11814-010-0481-3 · 1.24 Impact Factor
  • Abbas Khoshhal, Masoud Rahimi, Ammar Abdulaziz Alsairafi
    [Show abstract] [Hide abstract]
    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. DOI:10.1080/10407782.2011.561117 · 1.85 Impact Factor