Simulation of thermally developing laminar flow in partially filled porous pipes under wall suction

This study numerically investigates fluid flow and heat transfer enhancement of a two-dimensional developing laminar flow in an axisymmetric pipe with partially filled porous material attached to the wall. the effects of porous layer in the range of 0 ≤ δ /r < 1 and darcy number in the range of 10^- 6 ≤ da ≤ 10^- 4 are investigated. it is found that thermal entrance length increases with porous layer thickness and is longer than a plain pipe. in addition, the dependence of nusselt number on the thickness of the porous layer is not monotonic. a critical value of the porous layer thickness exists at which the nusselt number value reaches the minimum. as the porous layer is thickening, more fluid is pushed towards the middle of the pipe and less fluid goes through the porous layer in comparison with the case that the porous layer is located in the center. in this case, the heat convection is reduced relative to heat conduction due to the physical contact between the solid matrix and the wall surface.