The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
Sefik Bilir - One of the best experts on this subject based on the ideXlab platform.
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transient conjugated heat transfer in thermally developing laminar Flow in thick walled pipes and minipipes with time periodically varying wall temperature boundary condition
International Journal of Heat and Mass Transfer, 2016Co-Authors: Aziz Hakan Altun, Sefik Bilir, Ali AtesAbstract:Abstract Transient conjugated heat transfer for thermally developing laminar Flow in thick walled pipes is analyzed involving two-dimensional wall and axial fluid conduction. A two-regional, initially isothermal pipe is considered and the problem is handled for Hydrodynamically Developed Flow with periodically time-varying outer wall temperature in the downstream region. The problem is solved numerically by a finite-difference method and a parametric study is done to analyse the effects of four defining parameters namely, wall thickness ratio, wall-to-fluid conductivity ratio, wall-to-fluid thermal diffusivity ratio, the Peclet number and also the effect of angular frequency. Considerable amount of heat is transferred through the upstream region due to both wall and fluid axial conduction. Heat transfer characteristics change periodically in time similar to the periodic change in the outer wall temperature. The results are found to be affected by the parameter values and by the angular frequency.
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unsteady conjugated heat transfer in thick walled pipes involving two dimensional wall and axial fluid conduction with uniform heat flux boundary condition
International Journal of Heat and Mass Transfer, 2010Co-Authors: Ali Ates, Selcuk Darici, Sefik BilirAbstract:Transient conjugated heat transfer in thick walled pipes for thermally developing laminar Flow is investigated involving two-dimensional wall and axial fluid conduction. The problem is solved numerically by a finite-difference method for Hydrodynamically Developed Flow in a two-regional pipe, initially isothermal in which the upstream region is insulated and the downstream region is subjected to a suddenly applied uniform heat flux. A parametric study is done to analyze the effects of four defining parameters namely, wall thickness ratio, wall-to-fluid thermal conductivity ratio, wall-to-fluid thermal diffusivity ratio and the Peclet number. The results are given by non-dimensional interfacial heat flux values, and it is observed that, heat transfer characteristics are strongly dependent on the parameter values.
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Transient conjugated heat transfer in thick walled pipes with convective boundary conditions
International Journal of Heat and Mass Transfer, 2003Co-Authors: Sefik Bilir, Ali AtesAbstract:Abstract Transient conjugated heat transfer for laminar Flow in the thermal entrance region of pipes is investigated by considering two dimensional wall and axial fluid conduction. The problem is handled for an initially isothermal, infinitely long, thick-walled and two-regional pipe for which the upstream region is insulated and solved numerically by a finite difference method for Hydrodynamically Developed Flow with a step change in the ambient fluid temperature in the heated downstream region. A parametric study is done to analyse the effects of five defining parameters namely, wall thickness ratio, wall-to-fluid conductivity ratio, wall-to-fluid thermal diffusivity ratio, the Peclet number and the Biot number.
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Numerical solution of Graetz problem with axial conduction
Numerical Heat Transfer Part A: Applications, 1992Co-Authors: Sefik BilirAbstract:Heat transfer in the thermal entrance region of pipes is analyzed by the finite-difference method including the effect of axial fluid conduction. A Hydrodynamically Developed Flow through a two-region pipe is investigated for constant surface temperatures by a step change and for insulated upstream and uniform wall heat flux in the downstream region. The rate of convergence is enhanced by discretizing the governing differential equation by an exact profile obtained from the analytical solution of the one-dimensional conduction-convection problem.
Alain Degiovanni - One of the best experts on this subject based on the ideXlab platform.
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Impedance identification in a Hydrodynamically Developed Flow
International Journal of Thermal Sciences, 2019Co-Authors: Anas El Maakoul, Alain DegiovanniAbstract:Abstract This paper is an extension of the previous work by Degiovanni & Remy (2014) [1], where it was analytically demonstrated that the appropriate representation of interfacial heat transfer consists in defining a generalized impedance Z . The latter is intrinsic to the Flow and does not depend on the thermal boundary conditions. In this work, we demonstrate the pertinence of this representation for complex Flow problems where a direct analytical formula of the impedance cannot be calculated or can only be presented in terms of complex equations that are not easily applicable. The general idea is to perform numerical experiments to estimate this impedance using an inverse method, thus obtaining Green's function. Numerical simulations are carried out using the software Fluent for each Flow problem. We will show that by using the inverse method on the numerical results for a constant temperature boundary condition, we are able to calculate the intrinsic Green's function for each Flow problem, from which we can accurately calculate the thermal characteristics for any other thermal boundary condition, particularly for a constant heat flux.
Ali Ates - One of the best experts on this subject based on the ideXlab platform.
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transient conjugated heat transfer in thermally developing laminar Flow in thick walled pipes and minipipes with time periodically varying wall temperature boundary condition
International Journal of Heat and Mass Transfer, 2016Co-Authors: Aziz Hakan Altun, Sefik Bilir, Ali AtesAbstract:Abstract Transient conjugated heat transfer for thermally developing laminar Flow in thick walled pipes is analyzed involving two-dimensional wall and axial fluid conduction. A two-regional, initially isothermal pipe is considered and the problem is handled for Hydrodynamically Developed Flow with periodically time-varying outer wall temperature in the downstream region. The problem is solved numerically by a finite-difference method and a parametric study is done to analyse the effects of four defining parameters namely, wall thickness ratio, wall-to-fluid conductivity ratio, wall-to-fluid thermal diffusivity ratio, the Peclet number and also the effect of angular frequency. Considerable amount of heat is transferred through the upstream region due to both wall and fluid axial conduction. Heat transfer characteristics change periodically in time similar to the periodic change in the outer wall temperature. The results are found to be affected by the parameter values and by the angular frequency.
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unsteady conjugated heat transfer in thick walled pipes involving two dimensional wall and axial fluid conduction with uniform heat flux boundary condition
International Journal of Heat and Mass Transfer, 2010Co-Authors: Ali Ates, Selcuk Darici, Sefik BilirAbstract:Transient conjugated heat transfer in thick walled pipes for thermally developing laminar Flow is investigated involving two-dimensional wall and axial fluid conduction. The problem is solved numerically by a finite-difference method for Hydrodynamically Developed Flow in a two-regional pipe, initially isothermal in which the upstream region is insulated and the downstream region is subjected to a suddenly applied uniform heat flux. A parametric study is done to analyze the effects of four defining parameters namely, wall thickness ratio, wall-to-fluid thermal conductivity ratio, wall-to-fluid thermal diffusivity ratio and the Peclet number. The results are given by non-dimensional interfacial heat flux values, and it is observed that, heat transfer characteristics are strongly dependent on the parameter values.
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Transient conjugated heat transfer in thick walled pipes with convective boundary conditions
International Journal of Heat and Mass Transfer, 2003Co-Authors: Sefik Bilir, Ali AtesAbstract:Abstract Transient conjugated heat transfer for laminar Flow in the thermal entrance region of pipes is investigated by considering two dimensional wall and axial fluid conduction. The problem is handled for an initially isothermal, infinitely long, thick-walled and two-regional pipe for which the upstream region is insulated and solved numerically by a finite difference method for Hydrodynamically Developed Flow with a step change in the ambient fluid temperature in the heated downstream region. A parametric study is done to analyse the effects of five defining parameters namely, wall thickness ratio, wall-to-fluid conductivity ratio, wall-to-fluid thermal diffusivity ratio, the Peclet number and the Biot number.
Anas El Maakoul - One of the best experts on this subject based on the ideXlab platform.
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Impedance identification in a Hydrodynamically Developed Flow
International Journal of Thermal Sciences, 2019Co-Authors: Anas El Maakoul, Alain DegiovanniAbstract:Abstract This paper is an extension of the previous work by Degiovanni & Remy (2014) [1], where it was analytically demonstrated that the appropriate representation of interfacial heat transfer consists in defining a generalized impedance Z . The latter is intrinsic to the Flow and does not depend on the thermal boundary conditions. In this work, we demonstrate the pertinence of this representation for complex Flow problems where a direct analytical formula of the impedance cannot be calculated or can only be presented in terms of complex equations that are not easily applicable. The general idea is to perform numerical experiments to estimate this impedance using an inverse method, thus obtaining Green's function. Numerical simulations are carried out using the software Fluent for each Flow problem. We will show that by using the inverse method on the numerical results for a constant temperature boundary condition, we are able to calculate the intrinsic Green's function for each Flow problem, from which we can accurately calculate the thermal characteristics for any other thermal boundary condition, particularly for a constant heat flux.
Jawad Lahjomri - One of the best experts on this subject based on the ideXlab platform.
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Convective heat transfer for a gaseous slip Flow in micropipe and parallel-plate microchannel with uniform wall heat flux: effect of axial heat conduction
Indian Journal of Physics, 2018Co-Authors: Youssef Haddout, E. Essaghir, Abdelaziz Oubarra, Jawad LahjomriAbstract:Thermally developing laminar slip Flow through a micropipe and a parallel plate microchannel, with axial heat conduction and uniform wall heat flux, is studied analytically by using a powerful method of self-adjoint formalism. This method results from a decomposition of the elliptic energy equation into a system of two first-order partial differential equations. The advantage of this method over other methods, resides in the fact that the decomposition procedure leads to a selfadjoint problem although the initial problem is apparently not a self-adjoint one. The solution is an extension of prior studies and considers a first order slip model boundary conditions at the fluid-wall interface. The analytical expressions for the developing temperature and local Nusselt number in the thermal entrance region are obtained in the general case. Therefore, the solution obtained could be extended easily to any Hydrodynamically Developed Flow and arbitrary heat flux distribution. The analytical results obtained are compared for select simplified cases with available numerical calculations and they both agree. The results show that the heat transfer characteristics of Flow in the thermal entrance region are strongly influenced by the axial heat conduction and rarefaction effects which are respectively characterized by Péclet and Knudsen numbers.
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convective heat transfer for a gaseous slip Flow in micropipe and parallel plate microchannel with uniform wall heat flux effect of axial heat conduction
Indian Journal of Physics, 2018Co-Authors: Youssef Haddout, E. Essaghir, Abdelaziz Oubarra, Jawad LahjomriAbstract:Thermally developing laminar slip Flow through a micropipe and a parallel plate microchannel, with axial heat conduction and uniform wall heat flux, is studied analytically by using a powerful method of self-adjoint formalism. This method results from a decomposition of the elliptic energy equation into a system of two first-order partial differential equations. The advantage of this method over other methods, resides in the fact that the decomposition procedure leads to a selfadjoint problem although the initial problem is apparently not a self-adjoint one. The solution is an extension of prior studies and considers a first order slip model boundary conditions at the fluid-wall interface. The analytical expressions for the developing temperature and local Nusselt number in the thermal entrance region are obtained in the general case. Therefore, the solution obtained could be extended easily to any Hydrodynamically Developed Flow and arbitrary heat flux distribution. The analytical results obtained are compared for select simplified cases with available numerical calculations and they both agree. The results show that the heat transfer characteristics of Flow in the thermal entrance region are strongly influenced by the axial heat conduction and rarefaction effects which are respectively characterized by Peclet and Knudsen numbers.
