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Heat Transfer Problems (heat + transfer_problem)

Distribution by Scientific Domains

Engineering	77%

Selected Abstracts

Homogenization technique for transient heat transfer in unidirectional composites

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2003
Marcin Kami
Abstract The article presented is devoted to the homogenization of transient heat transfer problems in unidirectional composites. Mathematical model is based on the effective modules method applied to unidirectional periodic composites,the effective heat conductivity is calculated in the closed form; the effective volumetric heat capacity for the entire composite is obtained by simple spatial averaging. Such a homogenization scheme makes it possible to significantly simplify numerical analysis of transient heat phenomena in various types of unidirectional composites with complicated microgeometry. The comparison of transient heat transfer problem for the composite in real and homogenized configuration is carried out using a specially adopted finite element method computer program. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Numerical approximation of the heat transfer between domains separated by thin walls

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2006
Ramon Codina
Abstract In this paper, we analyse the numerical approximation of the heat transfer problem between two subdomains that we will consider filled with a fluid and separated by a thin solid wall. First of all, we state the problem in the whole domain with discontinuous physical properties. As an alternative and under certain assumptions on the separating walls, a classical Robin boundary condition between the fluid domains is obtained, thus eliminating the solid wall, and according to which the heat flux is proportional to the temperature difference between the two subdomains. Apart from discussing the relation between both approaches, we consider their numerical approximation, considering different alternatives for the first case, that is, the case in which temperatures are also computed in the solid wall. Copyright © 2006 John Wiley & Sons, Ltd. [source]

k,l based hybrid LES/RANS approach and its application to heat transfer simulation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2004
Bowen Zhong
Abstract To improve the compatibility of a k,l based hybrid LES/RANS approach, a controllable transitional zone is introduced to bridge the RANS and LES zones. This allows blending of the very different modelled turbulence length scales in these regions. To obtain a smooth variation of the length scales and transitional zone parameters different weighting functions are proposed. Results show the ,RANS' region has significant coherent unsteadiness. For Unsteady RANS (URANS) theoretical correctness, a favourable spectral gap between the modelled and resolved scales is required. The use of unsteadiness damping and time step filtering to ensure this is explored. Approaches are tested for a plane channel flow and the flow over a matrix of surface mounted cubes. The capability of the new hybrid LES/RANS method in improving heat transfer prediction in a conjugate heat transfer problem is examined. Numerical tests show that, compared to the RANS simulation, the proposed hybrid LES/RANS scheme performs well for the flow with large scale unsteadiness. It is also effective for improving the prediction of heat transfer. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Homogenization of a composite medium with a thermal barrier

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 4 2004
Mongi Mabrouk
Abstract In this work, we consider a heat transfer problem between two periodic connected media exchanging a heat flux throughout their common interface. The interfacial exchange coefficient , is assumed to tend to zero or to infinity following a rate ,=,(,) when the size ,of the basic cell tends to zero. Three homogenized problems are determined according to the value of ,=lim,,0,/,. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Homogenization technique for transient heat transfer in unidirectional composites

Quasi-dual reciprocity boundary-element method for incompressible flow: Application to the diffusive,advective equation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2003
C. F. Loeffler
Abstract This work presents a new boundary-element method formulation called quasi-dual reciprocity formulation for heat transfer problems, considering diffusive and advective terms. The present approach has some characteristics similar to those of the so-called dual-reciprocity formulation; however, the mathematical developments of the quasi-dual reciprocity approach reduces approximation errors due to global domain interpolation. Some one- and two-dimensional examples are presented, the results being compared against those obtained from analytical and dual-reciprocity formulations. The method convergence is evaluated through analyses where the mesh is successively refined for various Peclet numbers, in order to assess the effect of the advective term. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Performance analysis of IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2009
Dong-Liang Sun
Abstract Recently, an efficient segregated algorithm for incompressible fluid flow and heat transfer problems, called inner doubly iterative efficient algorithm for linked equations (IDEAL), has been proposed by the present authors. In the algorithm there exist inner doubly iterative processes for pressure equation at each iteration level, which almost completely overcome two approximations in SIMPLE algorithm. Thus, the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate and stability of solution process. However, validations have only been conducted for two-dimensional cases. In the present paper the performance of the IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems is analyzed and a systemic comparison is made between the algorithm and three other most widely used algorithms (SIMPLER, SIMPLEC and PISO). By the comparison of five application examples, it is found that the IDEAL algorithm is the most robust and the most efficient one among the four algorithms compared. For the five three-dimensional cases studied, when each algorithm works at its own optimal under-relaxation factor, the IDEAL algorithm can reduce the computation time by 12.9,52.7% over SIMPLER algorithm, by 45.3,73.4% over SIMPLEC algorithm and by 10.7,53.1% over PISO algorithm. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Heat transfer in composite materials with Stefan,Boltzmann interface conditions

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2008
Yang Gufan
Abstract In this paper, we discuss nonstationary heat transfer problems in composite materials. This problem can be formulated as the parabolic equation with Stefan,Boltzmann interface conditions. It is proved that there exists a unique global classical solution to one-dimensional problems. Moreover, we propose a numerical algorithm by the finite difference method for this nonlinear transmission problem. Copyright © 2007 John Wiley & Sons, Ltd. [source]