ملخص: A study of flow regime and heat transfer in an annular heat exchanger partially filled with a porous medium is presented in this work. Constant heat flux and constant wall temperature boundary conditions on the inner cylinder are considered, while the outer cylinder is assumed adiabatic. The study is for both the thermal entry region and the thermally fully developed region. The flow in the porous region is modelled either by the Darcy-Brinkman equation for which an exact solution is developed or by the Darcy-Brinkman-Forchheimer equation in order to take into account inertial effects. For this case a numerical solution based on a control volume method is discussed. The results emphasize the effect of the porous layer attached to the inner cylinder on the thermal development length and heat transfer rate. It is shown that the porous substrate reduces the thermal entry length. When the effective thermal conductivity of the saturated porous medium is of the order of the fluid thermal conductivity, the local Nusselt does not vary monotonically with the thickness of the substrate. However, the use of a porous matrix always leads to an increase in the heat transfer rate provided its thermophysical properties and thickness are well chosen.Les transferts thermiques dans un echangeur annulaire partiellement ou totalement rempli par un milieu poreux sont etudies dans cet article. On suppose le regime dynamique etabli, le cylindre exterieur isole et on traite les deux cas d'un cylindre interieur isotherme ou chauffe a flux constant. L'etude est menee depuis le debut de la zone de chauffage jusqu'a l'etablissement du regime thermique. Dans la couche poreuse, deposee sur le cylindre interieur, l'ecoulement est modelise par l'equation generale de Darcy-Brinkman-Forchheimer. Lorsque les effets inertiels sont negligeables, on presente une solution analytique complete applicable en regime thermique etabli pour un cylindre interieur chauffea flux constant. Cette solution sert, en particulier, a valider les simulations numeriques basees sur la methode des volumes finis. On etudie ensuite l'influence de la couche poreuse sur l'etablissement du regime thermique et sur le transfert de chaleur. On montre qu'un choix judicieux de la matrice poreuse permet d'augmenter les echanges thermiques par convection.

لغة: فرنسية