Numerical analysis of heat transfer enhancement in a double pipe heat exchanger with porous fins

Abstract

PurposeThe aim is to study numerically the heat transfer enhancement in a double pipe heat exchanger by using porous fins attached at the external wall of the inner cylinder.Design/methodology/approachThe Brinkman‐Forchheimer extended Darcy model is used in the porous regions. The differential equations subjected to the boundary conditions are solved numerically using the finite volume method. Numerical calculations are performed for a wide range of Darcy number (10−6≤Da≤10−1), porous fins height (0≤Hp≤1) and spacing (0≤Lf≤39) and thermal conductivity ratio (1≤Rk≤100). The effects of these parameters are considered in order to look for the most appropriate properties of the porous fins that allow optimal heat transfer enhancement.FindingsThe results obtained show that the insertion of porous fins may alter substantially the flow pattern depending on their permeability, height and spacing. Concerning the heat transfer effect, it is found that the use of porous fins may enhance the heat transfer in comparison to the fluid case and that the rate of improvement depends on their geometrical and thermo‐physical properties. Performance analysis indicated that more net energy gain may be achieved as the thermal conductivity ratio increases especially at high Darcy numbers and heights.Research limitations/implicationsThe results obtained in this work are valid for double pipe heat exchangers with the same fluid flowing at the same flow rate in the two ducts and for the case of an inner cylinder of negligible thermal resistance.Practical implicationsThe results obtained in this study can be used in the design of heat exchangers.Originality/valueThis study provides an interesting method to improve heat transfer in a double pipe heat exchanger by use of porous fins.

Heat transfer enhancement through porous fins: A comprehensive review of recent developments and innovations

“…Besides that viscous shear at the boundary wall, variable porosity as well as thermal dispersion also plays a major role in the model. In many applications, the Brinkman-extended Darcy and Brinkman–Forchheimer-extended Darcy 36–38 have also been used to estimate fluid and heat flow through porous media especially for high Darcy number.…”

Optimal hydrothermal design of internal flow pipe with insertion of straight and helical metal foam fins

“…They concluded that the rate of heat transfer was increased when the porous media structures were in a staggered arrangement. Kahalrras and Targui 10 studied numerically the enhancement of heat transfer in a double pipe heat exchanger, where porous fins were installed at the outer surface of the inner pipe. They found an improvement in the heat transfer rate in comparison with the case of the nonuse of porous fins.…”

Analysis of two‐dimensional porous fins with variable thermal conductivity

“…Kiwan introduced a new parameter called S H by using Rayleigh and Darcy numbers, thermal conductivity ratio, and length thickness ratio and found that increasing S H by increasing either Darcy or Rayleigh numbers increases the heat transfer rate from the fin. Kahalerras and Targui investigated the performance of a double pipe heat exchanger fitted with porous fins. The results showed that the insertion of porous fins may change the flow pattern depending on their permeability, height, and spacing.…”