Conjugate heat transfer in an annulus with heated longitudinal and transversal fins

In this work, we numerically study the three-dimensional conjugate mixed convection heat transfer in a horizontal annulus equipped by longitudinal and transversal fins attached on its internal surface of outer cylinder. The external pipe and fins are heated by an electrical current passing through their small thickness while the inner pipe is kept adiabatic. We investigate the effects of adding longitudinal and transversal fins on the fluid dynamic and the heat transfer performances. The number of longitudinal fins varies from two to eight fins while the number of transvers ones is equal to four. The convection in the fluid domain is conjugated to thermal conduction in the pipes and fins solid thickness. The physical properties of the fluid are thermal dependent and the heat losses from the external pipe surface to the surrounding environment are taken account. The model equations of continuity, momenta and energy are numerically solved by the finite volume method with a second order spatiotemporal discretization. The Prandtl, the Reynolds and the Grashof numbers are fixed at 8.082, 399.02 and 12801 respectively. The obtained results showed that the axial Nusselt number increases with the increasing of number of fins. Moreover, the longitudinal fins configuration showed a more significant improvement in heat transfer than that of the transverse fins.