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Kacem Mansouri - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of laminar forced convection for a non newtonian nanofluids flowing inside an Elliptical Duct under convective boundary condition
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:The purpose of this study is to investigate the thermal response of the laminar non-Newtonian fluid flow in Elliptical Duct subjected to a third-kind boundary condition with a particular interest to a non-Newtonian nanofluid case. The effects of Biot number, aspect ratio and fluid flow behavior index on the heat transfer have been examined carefully.,First, the mathematical problem has been formulated in dimensionless form, and then the curvilinear Elliptical coordinates transform is applied to transform the original Elliptical shape of the Duct to an equivalent rectangular numerical domain. This transformation has been adopted to overcome the inherent mathematical deficiency due to the dependence of the ellipsis contour on the variables x and y. The yielded problem has been successfully solved using the dynamic alternating direction implicit method. With the available temperature field, several parameters have been computed for the analysis purpose such as bulk temperature, Nusselt number and heat transfer coefficient.,The results showed that the use of Elliptical Duct enhances significantly the heat transfer coefficient and reduces the Duct’s length needed to achieve the thermal equilibrium. For some cases, the reDuction in the Duct’s length can reach almost 50 per cent compared to the circular pipe. In addition, the analysis of the non-Newtonian nanofluid case showed that the addition of nanoparticles to the base fluid improves the heat transfer coefficient up to 25 per cent. The combination of using an Elliptical Duct and the addition of nanoparticles has a spectacular effect on the overall heat transfer coefficient with an enhancement of 50-70 per cent. From the engineering applications view, the results demonstrate the potential of Elliptical Duct in building light-weighted compact shell-and-tube heat exchangers.,A complete investigation of the heat transfer of a fully developed laminar flow of power law fluids in Elliptical Ducts subject to the convective boundary condition with application to non-Newtonian nanofluids is addressed.
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an analytical study of the periodic laminar forced convection of non newtonian nanofluid flow inside an Elliptical Duct
International Journal of Heat and Mass Transfer, 2018Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:Abstract In this study, an analytical solution was obtained for a laminar forced convection of non-Newtonian nanofluid flowing inside an Elliptical Duct, with inlet temperature varying periodically with the time. The solution was obtained using the Generalized Integral Transform Technique (GITT). The thermal behavior of Cu-water non-Newtonian nanofluid, described by the power-law model was investigated. Also, an accurate correlation was established to estimate the thermal length required to achieve 99% of the amplitude attenuation. The results show a significant effect of aspect ratio β/α and fluid behavior index on the temperature amplitude reDuction. For instance, an Elliptical Duct with β/α = 0.25 reduces the thermal length Lth more than 50% compared with circular Duct. Adding nanoparticles until 5% increases the heat transfer coefficient up to 27% for the cylindrical tube. Besides, the heat transfer coefficient is improved over 42% relatively to the cylindrical configuration by reducing the aspect ratio to 0.25. Therefore, adding 5% of nanoparticles both using an Elliptical Duct with β/α = 0.25, improves the mean heat transfer coefficient around 83% compared to the flow of water base fluid inside a cylindrical Duct.
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a numerical study of viscous dissipation effect on non newtonian fluid flow inside Elliptical Duct
Energy Conversion and Management, 2013Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:Abstract Laminar heat transfer inside Duct with Elliptical cross section, subjected to uniform wall temperature is studied by taking into account the viscous dissipation. The temperatures distributions are evaluated numerically by using a dynamic Alternating Direction Implicit method (dADI). Nusselt number (Nu) is presented graphically for various Brinkman number (Br) and aspect ratio for a non-Newtonian fluid described by the power law model. The results obtained showed a good agreement with those found in the literature for fluid flow in circular cross section Ducts and in Elliptical cross section without viscous dissipation effects. It is shown that in the fully developed region and for Br ≠ 0, Nusselt number has a fixed asymptotic value independent of Brinkman number (Br). In the thermally developing region, it is observed a single fixed point independent of heating or cooling condition which the numerical value is equal to the asymptotic Nusselt number. Another relevant feature is that in the fully developed region, the Nusselt number increases with the aspect ratio.
Haroun Ragueb - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of laminar forced convection for a non newtonian nanofluids flowing inside an Elliptical Duct under convective boundary condition
International Journal of Numerical Methods for Heat & Fluid Flow, 2019Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:The purpose of this study is to investigate the thermal response of the laminar non-Newtonian fluid flow in Elliptical Duct subjected to a third-kind boundary condition with a particular interest to a non-Newtonian nanofluid case. The effects of Biot number, aspect ratio and fluid flow behavior index on the heat transfer have been examined carefully.,First, the mathematical problem has been formulated in dimensionless form, and then the curvilinear Elliptical coordinates transform is applied to transform the original Elliptical shape of the Duct to an equivalent rectangular numerical domain. This transformation has been adopted to overcome the inherent mathematical deficiency due to the dependence of the ellipsis contour on the variables x and y. The yielded problem has been successfully solved using the dynamic alternating direction implicit method. With the available temperature field, several parameters have been computed for the analysis purpose such as bulk temperature, Nusselt number and heat transfer coefficient.,The results showed that the use of Elliptical Duct enhances significantly the heat transfer coefficient and reduces the Duct’s length needed to achieve the thermal equilibrium. For some cases, the reDuction in the Duct’s length can reach almost 50 per cent compared to the circular pipe. In addition, the analysis of the non-Newtonian nanofluid case showed that the addition of nanoparticles to the base fluid improves the heat transfer coefficient up to 25 per cent. The combination of using an Elliptical Duct and the addition of nanoparticles has a spectacular effect on the overall heat transfer coefficient with an enhancement of 50-70 per cent. From the engineering applications view, the results demonstrate the potential of Elliptical Duct in building light-weighted compact shell-and-tube heat exchangers.,A complete investigation of the heat transfer of a fully developed laminar flow of power law fluids in Elliptical Ducts subject to the convective boundary condition with application to non-Newtonian nanofluids is addressed.
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an analytical study of the periodic laminar forced convection of non newtonian nanofluid flow inside an Elliptical Duct
International Journal of Heat and Mass Transfer, 2018Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:Abstract In this study, an analytical solution was obtained for a laminar forced convection of non-Newtonian nanofluid flowing inside an Elliptical Duct, with inlet temperature varying periodically with the time. The solution was obtained using the Generalized Integral Transform Technique (GITT). The thermal behavior of Cu-water non-Newtonian nanofluid, described by the power-law model was investigated. Also, an accurate correlation was established to estimate the thermal length required to achieve 99% of the amplitude attenuation. The results show a significant effect of aspect ratio β/α and fluid behavior index on the temperature amplitude reDuction. For instance, an Elliptical Duct with β/α = 0.25 reduces the thermal length Lth more than 50% compared with circular Duct. Adding nanoparticles until 5% increases the heat transfer coefficient up to 27% for the cylindrical tube. Besides, the heat transfer coefficient is improved over 42% relatively to the cylindrical configuration by reducing the aspect ratio to 0.25. Therefore, adding 5% of nanoparticles both using an Elliptical Duct with β/α = 0.25, improves the mean heat transfer coefficient around 83% compared to the flow of water base fluid inside a cylindrical Duct.
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a numerical study of viscous dissipation effect on non newtonian fluid flow inside Elliptical Duct
Energy Conversion and Management, 2013Co-Authors: Haroun Ragueb, Kacem MansouriAbstract:Abstract Laminar heat transfer inside Duct with Elliptical cross section, subjected to uniform wall temperature is studied by taking into account the viscous dissipation. The temperatures distributions are evaluated numerically by using a dynamic Alternating Direction Implicit method (dADI). Nusselt number (Nu) is presented graphically for various Brinkman number (Br) and aspect ratio for a non-Newtonian fluid described by the power law model. The results obtained showed a good agreement with those found in the literature for fluid flow in circular cross section Ducts and in Elliptical cross section without viscous dissipation effects. It is shown that in the fully developed region and for Br ≠ 0, Nusselt number has a fixed asymptotic value independent of Brinkman number (Br). In the thermally developing region, it is observed a single fixed point independent of heating or cooling condition which the numerical value is equal to the asymptotic Nusselt number. Another relevant feature is that in the fully developed region, the Nusselt number increases with the aspect ratio.
Davood Toghraie - One of the best experts on this subject based on the ideXlab platform.
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numerical analysis of flow and heat transfer in an Elliptical Duct fitted with two rotating twisted tapes
International Communications in Heat and Mass Transfer, 2021Co-Authors: Yingqing Song, Niloufar Izadpanahi, Mohammad Ali Fazilati, Davood ToghraieAbstract:Abstract This study investigates the effects of using the rotating twisted tapes on fluid flow, heat transfer, and thermal performance of a Duct flow. The section of the channel is oval and with two rotating twisted tapes. The twisted tapes are analyzed in fixed and rotating cases with three different rotational speeds. The flow regime is laminar with Re = 50 to 1000 and heat flux of 5000 Wm−2 was applied to the outer surface of the wall. The height of twisted tapes is equivalent to 90% of the channel height which creates the secondary flow. The simulation results suggest that increasing the Re number increases both the Nu number and the pumping power, and increasing the Re number increases the Nu number in all cases. At each Re number, the lowest and the highest increments resulted by using the tapes are for cases of stationary and rotating tapes with maximum speed, respectively. Using the twisted tapes increases the average Nu number by 24 to 179% and pumping power requirement by 50 to 250% for the same Re numbers. The value of FOM is less than 1 in the case of using fixed tapes while it is above 1 for the rotating tape. The highest value of FOM is 1.55 which is for the highest rotating speed at the lowest inlet velocity.
Hitoshi Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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numerical analysis of secondary flow for viscoelastic fluid through Elliptical Duct
Transactions of the Japan Society of Mechanical Engineers. B, 1999Co-Authors: Hitoshi Sugiyama, Mitsunobu Akiyama, Norifumi KoideAbstract:The flow behavior of viscoelastic non-Newtonian fluid in circular and non-circular Ducts is of special engineering interest. Therefore a numerical analysis has been performed for viscoelastic non-Newtonian fluid in Elliptical Duct. Special attention is paid for the generation of secondary flow for laminar flow by using two kinds of constitutive equation, i.e., Maxwell and Reiner-Rivlin models. As for Maxwell model, body force caused by the elastic stress is approximated by linear source term. In calculation, viscosity was represented by adopting power-law fluid and boundary-fitted coordinate system was introduced as the method of coordinate transformation. The calculated results of two models show the secondary flow in Elliptical Duct as the same as theoretically analyzed by Green and Rivlin. Adding to the prediction of secondary flow, the generation mechanism of secondary flow has been argued by evaluating the proDuction terms of the transport equation for streamwise vorticity. As a result of this examination, it was found that the term of viscous diffusion and the term containing second normal stress difference played an important role in producing the secondary flow near the wall. At the same time, it is interested phenomenon that the circular direction of secondary flow for viscoelastic fluid is opposite sigh to that of secondary flow for Newtonian turbulent flow. As its cause, the present study clarified that the term containing second normal stress difference of viscoelastic fluid is the same type equation for that of turbulence, while the sign of its term for viscoelastic fluid is opposite to that for turbulent flow.
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experimental analysis of developing turbulent flow in a distorted Elliptical Duct by laser doppler velocimeter
Transactions of the Japan Society of Mechanical Engineers. B, 1998Co-Authors: Hitoshi Sugiyama, Mitsunobu Akiyama, Takeo WatanabeAbstract:An experimental study of developing turbulent flow in a distorted ellptical Duct was carried out at Reynolds number 0.988×105 by using laser-Doppler velocimeter. In a distorted Elliptical Duct, the configuration of cross section varies from Elliptical to circular and from circular to Elliptical along streamwise direction with a constant cross sectional area constant. Three components of velocity and the five of the five stress components were measured at seven different locations to clarify the development of turbulent structure. As a result of this experimental study, it was found that the distributions of streamwise velocity were influenced by the secondary flow and the averaged intensity of the secondary flow over cross section showed the maximum value at midway between inlet and outlet of a distorted Duct. Adding to these points, experimental results displayed that the secondary flow of the second kind at inlet section transformed into that of the first kind induced by pressure gradient at a little distance from the inlet and that of the first kind again transformed that of the second kind at the outlet section. The location of the maximum intensity of streamwise normal stress moves gradually from near upper wall to near side wall as the flow develops. The two kinds of shear stress between streamwise fluctuating velocity and cross sectional fluctuating velocity shows distributions different from each other.
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experimental analysis of fully developed turbulent flow in an Elliptical Duct by laser doppler anemometer
Transactions of the Japan Society of Mechanical Engineers. B, 1994Co-Authors: Hitoshi Sugiyama, Mitsunobu Akiyama, Yoshinori Yakuwa, Hideki WakayamaAbstract:An experimental study of a fully developed turbulent flow in an Elliptical Duct with an aspect ratio 2 : 1 was carrid out using a Laser-Doppler anemometer. Special attention was paid for the measurement of Reynolds stresses and the secondary flow of the second kind. In addition to these results, axial mean velocity and turbulent intensity of the central region were measured in the developing flow. Although it is very difficult to measure the secondary flow of the second kind because of its small intensity, this measurement system was able to determine a large eddy caused by the secondary flow in a quarter cross section. At the same time, a clear statement of the distribution of five of the six Reynolds stresses was clarified, showing their characteristic aspects. The axial mean velocity of the central region reaches maximum intensity in the middle of developing. This maximum intensity is a result of shear layer interaction effects as the boundary layers developing along the wall of the Elliptical Duct begin to merge.
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numerical analysis of developing turbulent flow in an Elliptical Duct by a reynolds stress model
Transactions of the Japan Society of Mechanical Engineers. B, 1992Co-Authors: Hitoshi Sugiyama, Mitsunobu Akiyama, Nao Ninomiya, Kenichi Saitoh, Masaru HirataAbstract:A numerical analysis has been performed for three-dimensional developing turbulent flow in an Elliptical Duct by a modified Reynolds stress equation model. Governing equations are transformed from the physical plane to the calculation plane by boundary-fitted coordinate systems. The calculated results are compared with the experimental data available. The predicted results of mean velocity along the axes and friction factor agree relatively well with the experimental data. The results of this analysis enable the prediction of the secondary flow of the second kind which characterizes noncircular Duct flow. At the same time, a clear statement of the distribution of the various Reynolds stresses is made, showing their characteristic aspects. The secondary flow of the second kind reaches maximum intensity in the midst of development. This is a result of shear layer interaction effects as the boundary layer developing along the wall of the Elliptical Duct begin to merge.
Yingqing Song - One of the best experts on this subject based on the ideXlab platform.
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numerical analysis of flow and heat transfer in an Elliptical Duct fitted with two rotating twisted tapes
International Communications in Heat and Mass Transfer, 2021Co-Authors: Yingqing Song, Niloufar Izadpanahi, Mohammad Ali Fazilati, Davood ToghraieAbstract:Abstract This study investigates the effects of using the rotating twisted tapes on fluid flow, heat transfer, and thermal performance of a Duct flow. The section of the channel is oval and with two rotating twisted tapes. The twisted tapes are analyzed in fixed and rotating cases with three different rotational speeds. The flow regime is laminar with Re = 50 to 1000 and heat flux of 5000 Wm−2 was applied to the outer surface of the wall. The height of twisted tapes is equivalent to 90% of the channel height which creates the secondary flow. The simulation results suggest that increasing the Re number increases both the Nu number and the pumping power, and increasing the Re number increases the Nu number in all cases. At each Re number, the lowest and the highest increments resulted by using the tapes are for cases of stationary and rotating tapes with maximum speed, respectively. Using the twisted tapes increases the average Nu number by 24 to 179% and pumping power requirement by 50 to 250% for the same Re numbers. The value of FOM is less than 1 in the case of using fixed tapes while it is above 1 for the rotating tape. The highest value of FOM is 1.55 which is for the highest rotating speed at the lowest inlet velocity.