The Experts below are selected from a list of 3081 Experts worldwide ranked by ideXlab platform
A. Barletta - One of the best experts on this subject based on the ideXlab platform.
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Buoyant Flow with Viscous Heating in a Vertical Circular Duct Filled with a Porous Medium
Transport in Porous Media, 2007Co-Authors: A. Barletta, E Magyari, I. Pop, L. StoreslettenAbstract:Combined, forced, and free flow in a vertical Circular Duct filled with a porous medium is investigated according to the Darcy–Boussinesq model. The effect of viscous dissipation is taken into account. It is shown that a thermal boundary condition compatible with fully developed and axisymmetric flow is either a linearly varying wall temperature in the axial direction or, only in the case of uniform velocity profile, an axial linear-exponential wall temperature change. The case of a linearly varying wall temperature corresponds to a uniform wall heat flux and includes the uniform wall temperature as a special case. A general analytical solution procedure is performed, by expressing the seepage velocity profile as a power series with respect to the radial coordinate. It is shown that, for a fixed thermal boundary condition, i.e., for a prescribed slope of the wall temperature, and for a given flow rate, there exist two solutions of the governing balance equations provided that the flow rate is lower than a maximum value. When the maximum value is reached, the dual solutions coincide. When the flow rate is higher than its maximum, no axisymmetric solutions exist.
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combined forced and free flow in a vertical Circular Duct subjected to non axisymmetric wall heating conditions
International Journal of Heat and Mass Transfer, 2007Co-Authors: A. Barletta, Stefano LazzariAbstract:Abstract The fully developed mixed convection flow in a vertical Circular Duct is investigated analytically, under the assumption of laminar parallel flow. A wall heat flux uniform in the axial direction and dependent on the angular coordinate is considered. As a consequence, the fluid temperature is three dimensional, since it changes in the radial, axial and angular directions. An analytical method based on Fourier series expansions of temperature and velocity fields is adopted to determine the velocity and the temperature distributions as well as the friction factor and the average Nusselt number. The general solution, expressed in terms of Bessel functions, is applied to study a case that has a special importance in technical applications: a Duct whose wall is half subject to a uniform heat flux and half adiabatic. The positive and negative threshold values of the ratio between the Grashof number Gr and the Reynolds number Re for the onset of the flow reversal phenomenon are determined. A comparison between the average Nusselt number for the considered non-axisymmetric case and that for the case of a Duct subject to a uniform wall heat flux is performed.
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forced convection with viscous dissipation in the thermal entrance region of a Circular Duct with prescribed wall heat flux
International Journal of Heat and Mass Transfer, 2007Co-Authors: A. Barletta, E MagyariAbstract:Abstract The thermal entrance forced convection in a Circular Duct with a prescribed wall heat flux distribution is studied under the assumptions of a fully developed laminar flow and of a negligible axial heat conDuction in the fluid, by taking into account the effect of viscous dissipation. The solution of the local energy balance equation is obtained analytically by employing the Laplace transform method. The effect of viscous dissipation is taken into account also in the region upstream of the entrance cross-section, by assuming an adiabatic preparation of the fluid. The latter hypothesis implies that the initial condition in the entrance cross-section is a non-uniform radial temperature distribution. Two special cases are investigated in detail: an axially uniform wall heat flux, a wall heat flux varying linearly in the axial direction.
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mixed convection flow in a vertical Circular Duct with time periodic boundary conditions steady periodic regime
International Journal of Heat and Mass Transfer, 2004Co-Authors: A. Barletta, Rossi E Di SchioAbstract:Mixed convection flow in a vertical Circular Duct subjected to a periodic sinusoidal temperature change at the wall is investigated. The analysis is performed by considering fully-developed parallel flow and steady-periodic regime. The local momentum and energy balance equations, together with the constraint equations which arise from the definition of mean velocity and mean temperature, are written in a dimensionless form and mapped into equations in the complex domain. One obtains two independent boundary value problems, which provide the mean value and the oscillating term of the velocity and temperature distributions. These boundary value problems are solved analytically, and the velocity and temperature distributions are obtained as functions of three parameters: the Prandtl number, Pr, the dimensionless frequency X, the ratio between the Grashof number Gr and the Reynolds number Re. The Fanning friction factor and the dimensionless heat flux are evaluated. 2004 Elsevier Ltd. All rights reserved.
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periodic forced convection with axial heat conDuction in a Circular Duct
International Journal of Heat and Mass Transfer, 2000Co-Authors: A. Barletta, Rossi E Di SchioAbstract:Abstract Stationary and laminar forced convection in a Circular Duct is analyzed in the case of a sinusoidal axial change of the wall heat flux such that the modulus of its mean value is either zero or equal to the amplitude. The effect of the axial heat conDuction in the fluid is taken into account. Reference is made to the thermally developed region where the temperature distribution can be expressed as the sum of a linear function and a periodic function of the axial coordinate. The temperature field as well as the local and mean Nusselt numbers are evaluated analytically. Comparisons with the solution in the absence of axial heat conDuction are performed.
Sujoy Kumar Saha - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of laminar flow of viscous oil through a Circular tube having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth
Heat and Mass Transfer, 2015Co-Authors: Sujoy Kumar SahaAbstract:The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a Circular Duct having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral axial corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a Circular Duct up to a certain value of fin parameter.
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Thermal and friction characteristics of laminar flow through a Circular Duct having helical screw-tape with oblique teeth inserts and wire coil inserts
Experimental Thermal and Fluid Science, 2015Co-Authors: Sarbendu Roy, Sujoy Kumar SahaAbstract:Abstract Helical screw-tape inserts and wire coil inserts both individually are enhancement techniques. Naturally, therefore, it is worthwhile to try their combinations as a potential enhancement technique. The experimental friction factor and Nusselt number data for laminar flow through a Circular Duct having helical screw-tape and wire coil inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with wire coil inserts perform significantly better than the individual enhancement technique acting alone for laminar flow through a Circular Duct up to a certain value of the fin parameter.
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laminar fluid flow and heat transfer through a Circular tube having spiral ribs and twisted tapes
Experimental Thermal and Fluid Science, 2015Co-Authors: Sujoy Kumar SahaAbstract:Abstract The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a Circular Duct having integral spiral rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a Circular Duct up to a certain value of fin parameter.
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experimental investigation of laminar flow of viscous oil through a Circular tube having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth
Experimental Thermal and Fluid Science, 2014Co-Authors: Sujoy Kumar SahaAbstract:Abstract The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a Circular Duct having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a Circular Duct up to a certain value of fin parameter.
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Thermo-fluid characteristics of laminar flow of viscous oil through a Circular tube having integral helical corrugations and fitted with centre-cleared twisted-tape
Heat and Mass Transfer, 2012Co-Authors: Sujoy Kumar Saha, G. L. DayanidhiAbstract:The experimental friction factor and Nusselt number data for laminar flow through a Circular Duct having integral helical corrugation and fitted with centre-cleared twisted-tape has been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the centre-cleared twisted tapes in combination with integral helical corrugation perform better than the individual enhancement technique acting alone for laminar flow through a Circular Duct up to a certain amount of twisted-tape centre-clearance.
E Zanchini - One of the best experts on this subject based on the ideXlab platform.
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forced convection in the thermal entrance region of a Circular Duct with slug flow and viscous dissipation
International Journal of Heat and Mass Transfer, 1997Co-Authors: A. Barletta, E ZanchiniAbstract:Abstract Slug flow forced convection in a Circular Duct is studied. The effect of viscous dissipation is analysed in the thermal entrance region. The temperature field and the local Nusselt number are determined analytically for any prescribed axial distribution of wall heat flux. Three examples are considered: a uniform wall heat flux, a linearly varying wall heat flux and an exponentially varying wall heat flux. In the case of a uniform wall heat flux, it is shown that viscous dissipation reduces the value of the local Nusselt number in the whole Duct. In the case of a linearly or exponentially increasing wall heat flux, viscous dissipation affects the local Nusselt number only in the thermal entrance region and becomes negligible in the fully developed region.
E Magyari - One of the best experts on this subject based on the ideXlab platform.
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Buoyant Flow with Viscous Heating in a Vertical Circular Duct Filled with a Porous Medium
Transport in Porous Media, 2007Co-Authors: A. Barletta, E Magyari, I. Pop, L. StoreslettenAbstract:Combined, forced, and free flow in a vertical Circular Duct filled with a porous medium is investigated according to the Darcy–Boussinesq model. The effect of viscous dissipation is taken into account. It is shown that a thermal boundary condition compatible with fully developed and axisymmetric flow is either a linearly varying wall temperature in the axial direction or, only in the case of uniform velocity profile, an axial linear-exponential wall temperature change. The case of a linearly varying wall temperature corresponds to a uniform wall heat flux and includes the uniform wall temperature as a special case. A general analytical solution procedure is performed, by expressing the seepage velocity profile as a power series with respect to the radial coordinate. It is shown that, for a fixed thermal boundary condition, i.e., for a prescribed slope of the wall temperature, and for a given flow rate, there exist two solutions of the governing balance equations provided that the flow rate is lower than a maximum value. When the maximum value is reached, the dual solutions coincide. When the flow rate is higher than its maximum, no axisymmetric solutions exist.
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forced convection with viscous dissipation in the thermal entrance region of a Circular Duct with prescribed wall heat flux
International Journal of Heat and Mass Transfer, 2007Co-Authors: A. Barletta, E MagyariAbstract:Abstract The thermal entrance forced convection in a Circular Duct with a prescribed wall heat flux distribution is studied under the assumptions of a fully developed laminar flow and of a negligible axial heat conDuction in the fluid, by taking into account the effect of viscous dissipation. The solution of the local energy balance equation is obtained analytically by employing the Laplace transform method. The effect of viscous dissipation is taken into account also in the region upstream of the entrance cross-section, by assuming an adiabatic preparation of the fluid. The latter hypothesis implies that the initial condition in the entrance cross-section is a non-uniform radial temperature distribution. Two special cases are investigated in detail: an axially uniform wall heat flux, a wall heat flux varying linearly in the axial direction.
Rossi E Di Schio - One of the best experts on this subject based on the ideXlab platform.
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mixed convection flow in a vertical Circular Duct with time periodic boundary conditions steady periodic regime
International Journal of Heat and Mass Transfer, 2004Co-Authors: A. Barletta, Rossi E Di SchioAbstract:Mixed convection flow in a vertical Circular Duct subjected to a periodic sinusoidal temperature change at the wall is investigated. The analysis is performed by considering fully-developed parallel flow and steady-periodic regime. The local momentum and energy balance equations, together with the constraint equations which arise from the definition of mean velocity and mean temperature, are written in a dimensionless form and mapped into equations in the complex domain. One obtains two independent boundary value problems, which provide the mean value and the oscillating term of the velocity and temperature distributions. These boundary value problems are solved analytically, and the velocity and temperature distributions are obtained as functions of three parameters: the Prandtl number, Pr, the dimensionless frequency X, the ratio between the Grashof number Gr and the Reynolds number Re. The Fanning friction factor and the dimensionless heat flux are evaluated. 2004 Elsevier Ltd. All rights reserved.
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periodic forced convection with axial heat conDuction in a Circular Duct
International Journal of Heat and Mass Transfer, 2000Co-Authors: A. Barletta, Rossi E Di SchioAbstract:Abstract Stationary and laminar forced convection in a Circular Duct is analyzed in the case of a sinusoidal axial change of the wall heat flux such that the modulus of its mean value is either zero or equal to the amplitude. The effect of the axial heat conDuction in the fluid is taken into account. Reference is made to the thermally developed region where the temperature distribution can be expressed as the sum of a linear function and a periodic function of the axial coordinate. The temperature field as well as the local and mean Nusselt numbers are evaluated analytically. Comparisons with the solution in the absence of axial heat conDuction are performed.