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C Ghenai - One of the best experts on this subject based on the ideXlab platform.
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new correlations for the Average Nusselt Number in squealer turbine blade tip
2014Co-Authors: C Ghenai, M Madani, I JanajrehAbstract:Numerical simulations of the flow field and heat transfer of squealer blade tip are performed in this study. The effects of the Reynolds Number, the clearance gap to width ratios (C/W = 5% - 15%) and the cavity depth to width ratios (D/W = 10% - 50%) on fluid flow and heat transfer characteristics are obtained. The temperature and velocity distributions inside the cavity, the local heat transfer coefficients, and the Average Nusselt Numbers for the pressure and suction sides of the turbine blade tip are determined. This paper presents the results of the effects of Reynolds Number, clearance gap and width ratios on the Nusslet Number for the pressure and suction sides of squealer turbine blade tip. The results show a good agreement with the experimental data obtained by Metzger and Bunker. New correlations for the Average Nusselt Numbers for turbine blade tip pressure and suction sides are presented.
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Average Nusselt Number for pressure and suction sides of squealer turbine blade tip
ASME JSME 2011 8th Thermal Engineering Joint Conference, 2011Co-Authors: C GhenaiAbstract:Numerical simulations of the flow field and heat transfer of squealer blade tip are performed in this study. The effect of Reynolds Number (Re = 10000–40000), the clearance gap to width ratios (C/W = 5%–15%) and the cavity depth to width ratios (D/W = 10%, 20% and 50%) on fluid flow and heat transfer characteristics are obtained. The temperature and velocity distributions inside the cavity, the local heat transfer coefficients, and the Average Nusselt Numbers for the pressure and suction sides of the turbine blade tip are determined. This paper presents the results of the effects of Reynolds Number, clearance gap and width ratios on the Nusslet Number for the pressure and suction sides of squealer turbine blade tip. The results show a good agreement with the experimental data obtained by Metzger and Bunker. New correlations for the Average Nusselt Numbers for turbine blade tip pressure and suction sides are presented.Copyright © 2011 by ASME
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Average Nusselt Number for Pressure and Suction Sides of Squealer Turbine Blade Tip
ASME JSME 2011 8th Thermal Engineering Joint Conference, 2011Co-Authors: C GhenaiAbstract:Numerical simulations of the flow field and heat transfer of squealer blade tip are performed in this study. The effect of Reynolds Number (Re = 10000–40000), the clearance gap to width ratios (C/W = 5%–15%) and the cavity depth to width ratios (D/W = 10%, 20% and 50%) on fluid flow and heat transfer characteristics are obtained. The temperature and velocity distributions inside the cavity, the local heat transfer coefficients, and the Average Nusselt Numbers for the pressure and suction sides of the turbine blade tip are determined. This paper presents the results of the effects of Reynolds Number, clearance gap and width ratios on the Nusslet Number for the pressure and suction sides of squealer turbine blade tip. The results show a good agreement with the experimental data obtained by Metzger and Bunker. New correlations for the Average Nusselt Numbers for turbine blade tip pressure and suction sides are presented.
Ali J. Chamkha - One of the best experts on this subject based on the ideXlab platform.
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Effects of a Rotating Cone on the Mixed Convection in a Double Lid-Driven 3D Porous Trapezoidal Nanofluid Filled Cavity under the Impact of Magnetic Field.
Nanomaterials (Basel Switzerland), 2020Co-Authors: Ali J. Chamkha, Fatih Selimefendigil, Hakan F. OztopAbstract:Effects of a rotating cone in 3D mixed convection of CNT-water nanofluid in a double lid-driven porous trapezoidal cavity is numerically studied considering magnetic field effects. The numerical simulations are performed by using the finite element method. Impacts of Richardson Number (between 0.05 and 50), angular rotational velocity of the cone (between −300 and 300), Hartmann Number (between 0 and 50), Darcy Number (between 10 − 4 and 5 × 10 − 2 ), aspect ratio of the cone (between 0.25 and 2.5), horizontal location of the cone (between 0.35 H and 0.65 H) and solid particle volume fraction (between 0 and 0.004) on the convective heat transfer performance was studied. It was observed that the Average Nusselt Number rises with higher Richardson Numbers for stationary cone while the effect is reverse for when the cone is rotating in clockwise direction at the highest supped. Higher discrepancies between the Average Nusselt Number is obtained for 2D cylinder and 3D cylinder configuration which is 28.5% at the highest rotational speed. Even though there are very slight variations between the Average Nu values for 3D cylinder and 3D cone case, there are significant variations in the local variation of the Average Nusselt Number. Higher enhancements in the Average Nusselt Number are achieved with CNT particles even though the magnetic field reduced the convection and the value is 84.3% at the highest strength of magnetic field. Increasing the permeability resulted in higher local and Average heat transfer rates for the 3D porous cavity. In this study, the aspect ratio of the cone was found to be an excellent tool for heat transfer enhancement while 95% enhancements in the Average Nusselt Number were obtained. The horizontal location of the cone was found to have slight effects on the Nusselt Number variations.
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NANOMATERIALS
'MDPI AG', 2020Co-Authors: Ali J. ChamkhaAbstract:Effects of a rotating cone in 3D mixed convection of CNT-water nanofluid in a double lid-driven porous trapezoidal cavity is numerically studied considering magnetic field effects. The numerical simulations are performed by using the finite element method. Impacts of Richardson Number (between 0.05 and 50), angular rotational velocity of the cone (between -300 and 300), Hartmann Number (between 0 and 50), Darcy Number (between 10-4 and 5x10-2), aspect ratio of the cone (between 0.25 and 2.5), horizontal location of the cone (between 0.35 H and 0.65 H) and solid particle volume fraction (between 0 and 0.004) on the convective heat transfer performance was studied. It was observed that the Average Nusselt Number rises with higher Richardson Numbers for stationary cone while the effect is reverse for when the cone is rotating in clockwise direction at the highest supped. Higher discrepancies between the Average Nusselt Number is obtained for 2D cylinder and 3D cylinder configuration which is 28.5% at the highest rotational speed. Even though there are very slight variations between the Average Nu values for 3D cylinder and 3D cone case, there are significant variations in the local variation of the Average Nusselt Number. Higher enhancements in the Average Nusselt Number are achieved with CNT particles even though the magnetic field reduced the convection and the value is 84.3% at the highest strength of magnetic field. Increasing the permeability resulted in higher local and Average heat transfer rates for the 3D porous cavity. In this study, the aspect ratio of the cone was found to be an excellent tool for heat transfer enhancement while 95% enhancements in the Average Nusselt Number were obtained. The horizontal location of the cone was found to have slight effects on the Nusselt Number variations
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Natural convection of multi-walled carbon nanotube–Fe3O4/water magnetic hybrid nanofluid flowing in porous medium considering the impacts of magnetic field-dependent viscosity
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: S.a.m. Mehryan, Mohsen Izadi, Zafar Namazian, Ali J. ChamkhaAbstract:The study ahead deals with the natural convection of MWCN–Fe3O4/water magnetic hybrid nanofluid flowing in a porous medium. The flow domain is affected by an inclined magnetic field influencing the dynamic viscosity. The dependency of the flow and heat transfer characteristics on Rayleigh Number, Ra = 103–106; Hartman Number, Ha = 0–50; inclination angle of the magnetic field, ϕ = 0°–180°; magnetic Number, δ0 = 0–2.0; porosity, e = 0.1–0.9; Darcy Number, Da = 10−7–10−1;and volume fraction of the composite nanoparticles, φ = 0, 0.1 and 0.3% is studied numerically. At low Rayleigh Number Ra = 104, dispersing the nanocomposite particles increases the Average Nusselt Number Nuavg, while that decreases the Nuavg when Ra = 105 and 106. The dependency of viscosity on the magnetic field decreases the Nuavg at 0° < ϕ < 135°, which is due to an increase in overall viscosity of the nanofluid. After that (ϕ ≥ 135°), the Average Nusselt Number is greatly enhanced by increasing ϕ from 135° up to 180°. There is no meaningful change in Average Nusselt Number of the hybrid nanofluid by increasing the inclination angle of magnetic field in the absence of magnetic field-dependent viscosity (δ0 = 0).
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Effect of Inclination on Heat Transfer and Fluid Flow in a Finned Enclosure Filled with a Dielectric Liquid
Numerical Heat Transfer Part A: Applications, 2009Co-Authors: Nader Ben Cheikh, Ali J. Chamkha, Brahim Ben BeyaAbstract:The problem of two-dimensional natural convection flow of a dielectric fluid in a square inclined enclosure with a fin placed on the hot wall is investigated numerically. The fin thickness and length are 1/10 and 1/2 of the enclosure side, respectively. The Rayleigh Number is varied from 103 to 5 × 105 and the solid to fluid thermal conductivity ratio is fixed at 103. The enclosure tilt or inclination angle is varied from 0° to 90°. The streamlines and isotherms within the enclosure are produced and the heat transfer is calculated. It is found that for 2.5 × 104 ≤ Ra ≤ 2.5 × 105, the Average Nusselt Number is maximum when γ = 0° and minimum when γ = 90°. For Ra = 5 × 105, the values of enclosure tilt angle for which the Average Nusselt Number is maximum or minimum are completely different due to the transition to unsteady state. In this case, the maximum heat transfer is obtained for γ = 60°, while the minimum heat transfer is predicted for γ = 0°. Monomial correlations relating the Average Nusselt Number...
K.k. Sundaram - One of the best experts on this subject based on the ideXlab platform.
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Experimental Average Nusselt Number characteristics with inclined non-confined jet impingement of air for cooling application
Experimental Thermal and Fluid Science, 2016Co-Authors: S. B. Ingole, K.k. SundaramAbstract:Abstract Jet impingement is exceedingly operational for numerous field applications including electronics cooling and process industry. Its implementation comfort makes it common for many applications. The paper deals with investigation of heat transfer characteristics of a cooling flat surface. It is cooled by air jet impinged at an inclination of 15–75° to target plate. For understanding variation in cooling performance, comprehensive experiments are performed with different configurations of inclined jets on hot surface. For simplicity in using air, it is recommended for verity of applications as cooling fluid. Air Inclined jet with Reynolds Number in the range of 2000 ⩽ Re ⩽ 20,000 is examined for the circular Inclined jet. The target to inclined jet perpendicular height ( H ) is varied from 0.5 ⩽ H / D ⩽ 6.8 for understanding effect of H on cooling performance of different locations on target plate. The investigation leads to equations for Average Nusselt Number for inclined non-confined air jet for cooling applications.
Nawaf H. Saeid - One of the best experts on this subject based on the ideXlab platform.
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Unsteady Mixed Convection of a Confined Jet in a Fluid-Superposed High Porosity Medium
Numerical Heat Transfer Part A: Applications, 2009Co-Authors: Kok-cheong Wong, Nawaf H. SaeidAbstract:Numerical study of a confined jet impingement cooling of a fluid-superposed porous medium heated from below is conducted to investigate the oscillatory mixed convection. The effects of the Rayleigh Number (2 × 105 ≤ Ra ≤ 1 × 106) and the Darcy Number (1 × 10−5 ≤ Da ≤ 5 × 10−4) on the heat transfer are investigated for different Peclet Numbers. It is found that, the Average Nusselt Number increases with the increase in Darcy Number or Rayleigh Number. The values of Average Nusselt Number are found to oscillate with time for some combination of Rayleigh Numbers (Ra ≥ 4 × 105) and Peclet Numbers (200 ≤ Pe ≤ 1000), at which the oscillatory convection occurs. The oscillation of Average Nusselt Number is investigated for different porous medium height and porous medium-to-fluid heat capacity ratio.
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Jet impingement cooling of a horizontal surface in a confined porous medium : Mixed convection regime
International Journal of Heat and Mass Transfer, 2006Co-Authors: Nawaf H. Saeid, Abdulmajeed A. MohamadAbstract:Abstract In the present article the jet impingement cooling of heated portion of a horizontal surface immersed in a fluid saturated porous media is considered for investigation numerically. The jet direction is considered to be perpendicular from the top to the horizontal heated element; therefore, the external flow and the buoyancy driven flow are in opposite directions. The governing parameters in the present problem are Rayleigh Number, Peclet Number, jet width and the distance between the jet and the heated portion normalized to the length of the heated element. The results are presented in the mixed convection regime with wide ranges of the governing parameters with the limitation of the Darcy model. It is found for high values of Peclet Number that increasing either Rayleigh Number or jet width lead to increase the Average Nusselt Number. Narrowing the distance between the jet and the heated portion could increase the Average Nusselt Number as well. No steady-state solution can be found in some cases; when the external jet flow and the flow due to buoyancy are in conflict for domination. The results from the unsteady governing equations in these cases show oscillation of the Average Nusselt Number along the heated element with the time without reaching steady state.
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Analysis of free convection about a horizontal cylinder in a porous media using a thermal non-equilibrium model ☆
International Communications in Heat and Mass Transfer, 2006Co-Authors: Nawaf H. SaeidAbstract:The thermally non-equilibrium model is used to study the free convection from a horizontal cylinder immersed in porous media. The governing equations are transformed to dimensionless form by introducing the boundary layer dimensionless variables. The resultant parabolic system of differential equations is solved by using an implicit finite difference method based on Keller box algorithm. The results of the developed code are validated with different mesh sizes, which can be used as benchmark results for thermally equilibrium condition. Numerical results are obtained for non-equilibrium model to analyze the effect of the governing parameters, which are the heat transfer coefficient between the solid and fluid phases H and the porosity scaled thermal conductivity ratio Kr. The results show that increasing H or Kr leads to increase in the total Average Nusselt Number. The value of the Average Nusselt Number for both fluid and solid phases as well as the total Average Nusselt Number have approached the corresponding values of the thermally equilibrium model at high value of H×Kr. © 2005 Elsevier Ltd. All rights reserved.
Amgad M. Abbass - One of the best experts on this subject based on the ideXlab platform.
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Experimental study of free single jet impingement utilizing high concentration SiO2 nanoparticles water base nanofluid
Applied Thermal Engineering, 2019Co-Authors: Medhat M. Sorour, Wael M. El-maghlany, Mohamed A. Alnakeeb, Amgad M. AbbassAbstract:Abstract An experimental investigation was conducted in order to study heat transfer between a vertical free surface jet and a horizontal stainless steel heated plate. The jet was composed of water-SiO2 nanofluid with an Average particle size of 8 nm delivered from a fixed nozzle diameter of 6 mm. The results covered a wide range of jet Reynolds Number up to 40000, ten nanoparticle volume fractions (0% ≤ φ ≤ 8.5%), five jet aspect ratios (z/d = 0.5, 1, 2, 4 and 8) and plate radius to jet diameter ratio (r/d) up to 12.5. The experimental results illustrated that the enhancement of the Average Nusselt Number increases with the volume fraction and Reynolds Number. Therefore, the volume fraction can significantly provide a heat transfer enhancement of the Average Nusselt Number up to 80% for a volume fraction of 8.5% compared to pure water. Conversely, the effect of nozzle to plate aspect ratio (z/d) is not significant. Finally, a new heat transfer correlation has been proposed for the Average Nusselt Number as a function of Peclet Number, a nanoparticle volume fraction, a plate to jet diameter ratio and a nozzle to plate aspect ratio.
