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J S Saini - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on heat transfer enhancement due to v shaped perforated blocks in a Rectangular Duct of solar air heater
2014Co-Authors: Tabish Alam, R P Saini, J S SainiAbstract:Abstract In this work, the effect of geometrical parameters of the V-shaped perforated blocks on heat transfer and flow characteristics of Rectangular Duct, has been investigated experimentally. The experimental investigation encompassed the geometrical parameter namely, relative blockage height ( e / H ) of 0.4–1.0, relative pitch ratio ( P / e ) of 4–12 and open area ratio ( β ) of 5–25% at a fixed angle of attack ( α ) of 60°. The effect of V-shaped perforated blockages has been investigated for the range of Reynolds number from 2000 to 20,000. The maximum enhancement in Nusselt and friction factor has been found to be 6.76 and 28.84 times to that of smooth Duct, respectively. Thermohydraulic performance of V-shaped perforated blockages is also compared to that of V-shaped solid blockages for same geometrical parameters.
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investigations on thermo hydraulic performance due to flow attack angle in v down rib with gap in a Rectangular Duct of solar air heater
2012Co-Authors: Sukhmeet Singh, Subhash Chander, J S SainiAbstract:Abstract In this investigation, thermo-hydraulic performance of Rectangular Ducts roughened with a new configuration of ‘V-down rib having gap’ on one wide wall is determined. Small symmetrical gap equal to rib height is created at the centre of both legs of V of continuous V-down rib. The Duct has aspect ratio (AR) of 12 and the Reynolds number (Re) ranged from 3000 to 15,000. To simulate the indoor testing of solar air heater, the roughened side of Rectangular Duct is heated with constant heat flux electric heater while the other sides are insulated. The roughness has relative roughness height of 0.043 and relative roughness pitch of 8. Five rib roughened plates having flow-attack-angle (α) from 30° to 75° have been tested. The thermo-hydraulic performance parameter based on equal pumping power (η), friction factor (f) and Nusselt number (Nu), were found to be highest for α = 60°. The results obtained at α = 60° were compared with those of continuous V-down rib for same rib-roughness parameters.
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Experimental investigation on heat transfer and fluid flow characteristics of air flow in a Rectangular Duct with Multi v-shaped rib with gap roughness on the heated plate
2012Co-Authors: Anil Kumar, R P Saini, J S SainiAbstract:Abstract In this work, results of an experimental investigation of the effect of geometrical parameters of Multi v-shaped ribs with gap on heat transfer and fluid flow characteristics of Rectangular Duct with heated plate having rib roughness on its underside have been reported. The range of parameters for this study has been decided on the basis of practical considerations of the system and operating conditions of solar air heaters. The experimental investigation encompassed the Reynolds number (Re) range from 2000 to 20,000, relative width ratio (W/w) of 6, relative gap distance (Gd/Lv) of 0.24–0.80, relative gap width (g/e) of 0.5–1.5, relative roughness height (e/D) of 0.043,relative roughness pitch (P/e) of 10, angle of attack (α) of 60°. The maximum enhancement in Nusselt number and friction factor is observed to be 6.32–6.12 times of that of the smooth Duct, respectively. The thermo-hydraulic performance parameter is found to be the best for the relative gap distance of 0.69 and the relative gap width of 1.0.
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experimental investigation on heat transfer enhancement due to a gap in an inclined continuous rib arrangement in a Rectangular Duct of solar air heater
2008Co-Authors: K R Aharwal, B K Gandhi, J S SainiAbstract:Artificial roughness in the form of repeated ribs has been proposed as a convenient method for enhancement of thermal performance of solar air heaters. This paper presents the experimental investigation of heat transfer and friction factor characteristics of a Rectangular Duct roughened with repeated square cross-section split-rib with a gap, on one broad wall arranged at an inclination with respect to the flow direction. The Duct has a width to height ratio (W/H) of 5.84, relative roughness pitch (P/e) of 10, relative roughness height (e/Dh) of 0.0377, and angle of attack (α) of 60°. The gap width (g/e) and gap position (d/W) were varied in the range of 0.5–2 and 0.1667–0.667, respectively. The heat transfer and friction characteristics of this roughened Duct have been compared with those of the smooth Duct under similar flow condition. The effect of gap position and gap width has been investigated for the range of flow Reynolds numbers from 3000 to 18,000. The maximum enhancement in Nusselt number and friction factor is observed to be 2.59 and 2.87 times of that of the smooth Duct, respectively. The thermo-hydraulic performance parameter is found to be the maximum for the relative gap width of 1.0 and the relative gap position of 0.25.
Jawali C. Umavathi - One of the best experts on this subject based on the ideXlab platform.
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Fully developed magneto convection flow in a vertical Rectangular Duct
2020Co-Authors: Umavathi , Jawali C. UmavathiAbstract:[[abstract]]An analysis is performed to study the MHD free convection flow in a vertical Rectangular Duct for laminar and fully developed regime taking into consideration the effects of Ohmic heating and viscous dissipation. Numerical solutions are found using finite difference method of second-order accuracy. The effects of various physical parameters such as Hartmann number, aspect ratio, buoyancy parameter and circuit parameter are presented graphically. It is found that as Hartmann number, buoyancy parameter and aspect ratio increase, the upward and downward flow rates are increased for open circuit but decrease for short circuit.[[note]]SC
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numerical analysis of natural convective flow and heat transfer of nanofluids in a vertical Rectangular Duct using darcy forchheimer brinkman model
2017Co-Authors: Jawali C. Umavathi, Odelu Ojjela, K VajraveluAbstract:Abstract In this paper, natural convective flow and heat transfer of nanofluids in a vertical Rectangular Duct filled with porous matrix is investigated. The Darcy-Forchheimer-Brinkman model is used to represent the fluid transport within the porous medium covering the parametric ranges of 1 ≤ Gr ≤ 25,0 ≤ Br ≤ 8, and 0.0001 ≤ Da ≤ 100. Also, pure water and five different types of nanofluids ( Cu , diamond, TiO 2 , Ag and SiO 2 ) are used with a volume fraction range of 0% ≤ O ≤0.2%. The governing nonlinear, coupled partial differential equations for the two-dimensional laminar, steady flow and heat transfer are solved numerically by a finite difference method with second order accuracy. It is found that the heat transfer is enhanced due to the use of a nanofluid. Further, it is noticed that an increase in the Darcy or Grashof or Brinkman numbers, or the aspect ratio parameter increase the flow and heat transfer characteristics; whereas the inertial or the viscosity ratio parameters reduce the flow and heat transfer characteristics. It is observed from 2-D graphs that the fluid rise up from the middle portion of the vertical wall and flow down along the two horizontal walls forming symmetric rolls with clockwise and counter-clockwise rotation inside the cavity. The temperature contours in 2-D are smooth curves which span the entire enclosure, and they are generally symmetry with respect to the horizontal symmetric line. The results obtained reveal many interesting behaviors that warrant further study on the heat transfer enhancement due to the nanofluids.
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Influence of temperature dependent conDuctivity of a nanofluid in a vertical Rectangular Duct
2016Co-Authors: Jawali C. Umavathi, M.a. SheremetAbstract:Abstract Natural convective heat transfer and fluid flow in a vertical Rectangular Duct filled with a nanofluid is studied numerically assuming the thermal conDuctivity to be dependent on the fluid temperature. The transport equations for mass, momentum and energy formulated in dimensionless form are solved numerically using finite difference method. Particular efforts have been focused on the effects of the thermal conDuctivity variation parameter, Grashof number, Brinkman number, nanoparticles volume fraction, aspect ratio and type of nanoparticles on the fluid flow and heat transfer inside the cavity. It is found that the flow was enhanced for the increase in Grashof number, Brinkman number and aspect ratio for any values of conDuctivity variation parameter and for regular fluid and nanofluid. The heat transfer rate for regular fluid is less than that for the nanofluid for all governing parameters.
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effect of variable viscosity on free convection in a vertical Rectangular Duct
2015Co-Authors: Jawali C. Umavathi, Odelu OjjelaAbstract:Abstract This paper considers the heat transfer in a vertical Rectangular Duct filled with Newtonian fluid. The viscosity of the fluid is assumed to depend on the temperature. The governing fundamental equations are approximated by a system of nonlinear ordinary differential equations and are solved numerically by using the finite difference method. The steady-state velocity and temperature contours are shown graphically. Numerical results for the skin friction, volumetric flow rate and the rate of heat transfer are obtained and reported in a tabular form for various parametric conditions to show interesting aspects of the solution. The results show that the negative values of viscosity variation parameter show intense velocity contour in the lower half region of the Duct whereas positive values of viscosity variation parameter show the intense velocity contours in the upper half region of the Duct. The temperature contours remain almost linear for any variations of governing parameters for all values of viscosity variation parameter.
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free convective flow in a vertical Rectangular Duct filled with porous matrix for viscosity and conDuctivity variable properties
2015Co-Authors: Jawali C. UmavathiAbstract:Abstract Free convection over a vertical Rectangular Duct filled with porous matrix with variable viscosity and variable thermal conDuctivity is studied in this paper. We consider the two-dimensional steady laminar flow and Brinkman–Forchheimer extended Darcy model to define the porous medium. Using the appropriate variables the basic governing equations are transformed to non-dimensional governing equations. The fluid viscosity is assumed to vary exponentially with temperature whereas the thermal conDuctivity is assumed to vary linearly with temperature. One of the vertical walls of the Duct is cooled with constant temperature while the other wall is heated to constant but different temperature. The governing coupled nonlinear momentum and energy equations are solved numerically using finite difference method. The effect of pertinent parameters such as variable viscosity, variable thermal conDuctivity, Darcy number, inertial parameter, Grashof number, Brinkman number and aspect ratio on the velocity, temperature, volumetric flow rate, shear stress and heat transfer are discussed.
R Ellahi - One of the best experts on this subject based on the ideXlab platform.
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peristaltic propulsion of jeffrey nano liquid and heat transfer through a symmetrical Duct with moving walls in a porous medium
2020Co-Authors: Arshad Riaz, M M Bhatti, A Zeeshan, R EllahiAbstract:Abstract In this article, a computational study has been performed on the peristaltic propulsion of nanofluid flow through a porous Rectangular Duct. A non-Newtonian fluid model, i.e. Jeffrey model is considered to examine the behavior of nanoparticles. A Cartesian coordinate system is adopted for the three-dimensional Duct. Furthermore, the three-dimensional Rectangular Duct contains porous wavy walls. An approximation of long wavelength and small Reynolds number have been applied to formulate the governing equations of momentum, energy, continuity, and concentration equation. These resulting coupled partial differential equations are further solved using Homotopy perturbation method and Genetic algorithm with a combination of Nelder Mead method. The purpose of the Genetic algorithm and Nelder Mead method is to reduce the residual error. For this purpose, numerical comparison of residual error is presented with a Homotopy perturbation method.
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Peristaltic transport of Jeffrey fluid in a Rectangular Duct through a porous medium under the effect of partial slip: An application to upgrade industrial sieves/filters
2019Co-Authors: R Ellahi, F Hussain, F Ishtiaq, A HussainAbstract:The peristaltic transport of Jeffrey fluid through the Rectangular Duct is investigated. The effect of porosity under the influence of partial slip is also taken into consideration. The equations describing the flow transport along with boundary conditions are first made dimensionless using appropriate transformations and are then solved to get the exact solutions. The role of pressure rise generated by the fluid is also presented. The obtained results are examined graphically through pertinent parameters affecting the flow. The streamlines have also been displayed to analyse the trapping phenomenon.
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study of variable magnetic field on the peristaltic flow of jeffrey fluid in a non uniform Rectangular Duct having compliant walls
2016Co-Authors: M M Bhatti, R Ellahi, A ZeeshanAbstract:Abstract In this article, the effects of variable magnetic field on peristaltic flow of Jeffrey fluid in a non-uniform Rectangular Duct having compliant walls are investigated. The unsteady viscous incompressible electrically conDucting flow is considered. The variable magnetic field under long wavelength and low Reynolds number is taken into account. The exact solutions of nonhomogeneous governing equations are obtained through eigenfunction expansion method. Impact of variables reflecting the salient features of magnetic parameter, Jeffrey parameter, aspect ratio, wall tension and wall properties has been graphically pointed out. Trapping phenomenon is analyzed through stream lines. A suitable comparison has also been made with the prior results in the literature as a limiting case of the considered problem, for instance, by taking a Jeffrey parameter λ1 = 0, the presented result reduces to Newtonian fluid. It is worth mentioning that with the increment in magnetic field, it causes a reDuction in the velocity of the fluid. Comparison with the existing published results are also presented as a special case of our study and found that presents results are in excellent agreement.
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effects of hall and ion slip on mhd peristaltic flow of jeffrey fluid in a non uniform Rectangular Duct
2016Co-Authors: R Ellahi, M M Bhatti, Ioan PopAbstract:Purpose – The purpose of this paper is to theoretically study the problem of the peristaltic flow of Jeffrey fluid in a non-uniform Rectangular Duct under the effects of Hall and ion slip. An incompressible and magnetohydrodynamics fluid is also taken into account. The governing equations are modelled under the constraints of low Reynolds number and long wave length. Recent development in biomedical engineering has enabled the use of the periastic flow in modern drug delivery systems with great utility. Design/methodology/approach – Numerical integration is used to analyse the novel features of volumetric flow rate, average volume flow rate, instantaneous flux and the pressure gradient. The impact of physical parameters is depicted with the help of graphs. The trapping phenomenon is presented through stream lines. Findings – The results of Newtonian fluid model can be obtained by taking out the effects of Jeffrey parameter from this model. No-slip case is a special case of the present work. The results ob...
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peristaltic flow of couple stress fluid in a non uniform Rectangular Duct having compliant walls
2016Co-Authors: R Ellahi, M M Bhatti, Constantin Fetecau, Kambiz VafaiAbstract:The present study investigates the peristaltic flow of couple stress fluid in a non-uniform Rectangular Duct with compliant walls. Mathematical modeling is based upon the laws of mass and linear momentum. Analytic solutions are carried out by the eigen function expansion method under long-wavelength and low-Reynolds number approximations. The features of the flow characteristics are analyzed by plotting the graphs of various values of physical parameters of interest. Trapping bolus scheme is also presented through streamlines.
N G Razuvanov - One of the best experts on this subject based on the ideXlab platform.
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buoyancy effects in vertical Rectangular Duct with coplanar magnetic field and single sided heat load downward and upward flow
2018Co-Authors: I R Kirillov, D M Obukhov, V G Sviridov, N G Razuvanov, I A Belyaev, I I Poddubnyi, P I KostichevAbstract:Abstract The effects specific for downward and upward flows of liquid metal (LM) in a vertical Rectangular Duct in a coplanar magnetic field (MF) are investigated. The experiments were performed in the JIHT's test facility with a closed magnetohydrodynamic (MHD) mercury loop. The temperature and velocity fields were measured in the Duct with single-side heating in a coplanar magnetic field. The averaged temperature fields, wall temperature distributions, statistical characteristics of temperature fluctuation and longitudinal velocity profiles were obtained. The results for the downward and the upward flow under different flow conditions are compared.
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buoyancy effects in vertical Rectangular Duct with coplanar magnetic field and single sided heat load
2016Co-Authors: I R Kirillov, D M Obukhov, V G Sviridov, N G Razuvanov, I A Belyaev, I I Poddubnyi, L G Genin, V M Batenin, Yu N PyatnitskayaAbstract:Abstract This article investigates an effect which was found out in downward flow of liquid metal (LM) in vertical Rectangular Duct in coplanar magnetic field (MF). The experiments have been performed on facility which located in JIHT. This facility is magneto hydrodynamic (MHD) mercury close-loop. The temperature field measurements have been performed at one side heating conditions in coplanar magnetic field. The averaged temperature fields, wall temperature distributions and statistical characteristics of temperature fluctuation have been obtained. The strong influence of counter thermo-gravitational convection (TGC) on average and fluctuation parameters has been observed. The influence of TGC in magnetic field leads to developing of temperature low-frequency fluctuations with high magnitude. The temperature fluctuation amplitude in a wide range of operating conditions is higher than turbulence level.
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investigation of hydrodynamics and heat transfer at liquid metal downflow in a Rectangular Duct in a coplanar magnetic field
2016Co-Authors: I I Poddubnyi, N G RazuvanovAbstract:Hydrodynamics and heat transfer in a liquid metal downflow in a Rectangular Duct with an aspect ratio of approximately 3/1 in a coplanar magnetic field (MF) are studied upon inhomogeneous (one-sided) heating of the Duct. The flow in the heat-transfer Duct of the cooling system of a liquid-metal blanket module of the tokamak-type thermonuclear reactor is modeled. Experiments were carried out at the mercury magnetohydrodynamic (MHD) test facility, which is a part of the MHD-complex of Moscow Power Engineering Institute–Joint Institute for High Temperatures of the Russian Academy of Sciences. A probe technique is used for measurements in the flow. The studies are performed within the following ranges of regime parameters: Reynolds numbers Re = 10000–55000, Hartmann numbers Ha = 0–800, and Grashof numbers Grq = 0–6 × 108. Averaged profiles of velocity, temperature, temperature fluctuations of the flow, and Duct wall temperature are presented for two typical flow regimes. Detailed measurements are performed in the Duct cross-section distant from the heating beginning in the region of homogeneous MF. MF leads to the turbulent transport suppression, owing to which the temperature on the heated wall increases. A considerable influence of the heat-gravitational counter-convection, the interaction of which with the external MF leads in some regimes to the appearance and development of instabilities in the laminarized flow, is revealed under the downflow conditions. Generation of large-scale secondary vortices with the axis parallel to the MF inDuction causes temperature fluctuations of the abnormal intensity that considerably exceeds the level of turbulent fluctuations. Such temperature fluctuations easily penetrate into the Duct wall and can lead to the fatigue breakdown of thermonuclear reactor cooling paths. Ranges of unallowable regime parameters are determined and the boundary in coordinates Gr-Re is presented, where this effect is revealed or vanishes. The numerical simulation of studied parameters is performed under the conditions corresponding to the experiment. Computational results coincide satisfactorily with the experimental data in the flow regimes with large Reynolds numbers, where the effect associated with the development of instabilities caused by the heat-gravitational convection is absent or is relatively small.
I I Poddubnyi - One of the best experts on this subject based on the ideXlab platform.
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buoyancy effects in vertical Rectangular Duct with coplanar magnetic field and single sided heat load downward and upward flow
2018Co-Authors: I R Kirillov, D M Obukhov, V G Sviridov, N G Razuvanov, I A Belyaev, I I Poddubnyi, P I KostichevAbstract:Abstract The effects specific for downward and upward flows of liquid metal (LM) in a vertical Rectangular Duct in a coplanar magnetic field (MF) are investigated. The experiments were performed in the JIHT's test facility with a closed magnetohydrodynamic (MHD) mercury loop. The temperature and velocity fields were measured in the Duct with single-side heating in a coplanar magnetic field. The averaged temperature fields, wall temperature distributions, statistical characteristics of temperature fluctuation and longitudinal velocity profiles were obtained. The results for the downward and the upward flow under different flow conditions are compared.
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buoyancy effects in vertical Rectangular Duct with coplanar magnetic field and single sided heat load
2016Co-Authors: I R Kirillov, D M Obukhov, V G Sviridov, N G Razuvanov, I A Belyaev, I I Poddubnyi, L G Genin, V M Batenin, Yu N PyatnitskayaAbstract:Abstract This article investigates an effect which was found out in downward flow of liquid metal (LM) in vertical Rectangular Duct in coplanar magnetic field (MF). The experiments have been performed on facility which located in JIHT. This facility is magneto hydrodynamic (MHD) mercury close-loop. The temperature field measurements have been performed at one side heating conditions in coplanar magnetic field. The averaged temperature fields, wall temperature distributions and statistical characteristics of temperature fluctuation have been obtained. The strong influence of counter thermo-gravitational convection (TGC) on average and fluctuation parameters has been observed. The influence of TGC in magnetic field leads to developing of temperature low-frequency fluctuations with high magnitude. The temperature fluctuation amplitude in a wide range of operating conditions is higher than turbulence level.
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investigation of hydrodynamics and heat transfer at liquid metal downflow in a Rectangular Duct in a coplanar magnetic field
2016Co-Authors: I I Poddubnyi, N G RazuvanovAbstract:Hydrodynamics and heat transfer in a liquid metal downflow in a Rectangular Duct with an aspect ratio of approximately 3/1 in a coplanar magnetic field (MF) are studied upon inhomogeneous (one-sided) heating of the Duct. The flow in the heat-transfer Duct of the cooling system of a liquid-metal blanket module of the tokamak-type thermonuclear reactor is modeled. Experiments were carried out at the mercury magnetohydrodynamic (MHD) test facility, which is a part of the MHD-complex of Moscow Power Engineering Institute–Joint Institute for High Temperatures of the Russian Academy of Sciences. A probe technique is used for measurements in the flow. The studies are performed within the following ranges of regime parameters: Reynolds numbers Re = 10000–55000, Hartmann numbers Ha = 0–800, and Grashof numbers Grq = 0–6 × 108. Averaged profiles of velocity, temperature, temperature fluctuations of the flow, and Duct wall temperature are presented for two typical flow regimes. Detailed measurements are performed in the Duct cross-section distant from the heating beginning in the region of homogeneous MF. MF leads to the turbulent transport suppression, owing to which the temperature on the heated wall increases. A considerable influence of the heat-gravitational counter-convection, the interaction of which with the external MF leads in some regimes to the appearance and development of instabilities in the laminarized flow, is revealed under the downflow conditions. Generation of large-scale secondary vortices with the axis parallel to the MF inDuction causes temperature fluctuations of the abnormal intensity that considerably exceeds the level of turbulent fluctuations. Such temperature fluctuations easily penetrate into the Duct wall and can lead to the fatigue breakdown of thermonuclear reactor cooling paths. Ranges of unallowable regime parameters are determined and the boundary in coordinates Gr-Re is presented, where this effect is revealed or vanishes. The numerical simulation of studied parameters is performed under the conditions corresponding to the experiment. Computational results coincide satisfactorily with the experimental data in the flow regimes with large Reynolds numbers, where the effect associated with the development of instabilities caused by the heat-gravitational convection is absent or is relatively small.
