Numerical Study on the Effect of Geometrical Parameter on the Thermal-Hydraulic Performance of the Metal Foam Heat Exchanger

Abstract

A numerical study was conducted to examine the heat transfer and pressure drop of the metal foam-wrapped array heat exchanger. Effects of geometrical parameters, including arrangement of metal foam heat exchanger (two arrangement: fully-filled of metal foam while other have a gap between metal foam and the chamber walls), porosity, and the pore density on the thermal hydraulic performance of copper metal foam heat exchanger are examined. Numerical modelling was done considering the thermal non-equilibrium energy model and the Darcy-Forchheimer flow model for metal foam heat exchangers in the Star-CCM+ program version 2019. Four types of metal foams at fixed dimensional thickness of 0.91 with variable properties were adopted, where the pores density was 5PPI & 20PPI and the porosity was 89% and 95%. The heat exchanger system is simulated over a range of Reynolds number, based on tube diameter, from 1333 to 6555 with tubes heated at a constant wall temperature. The layout and geometry of the foam heat exchangers were compared with bare tube heat exchanger. It was found that At low porosity 89%, the configuration of metal foam heat exchanger that have pores density of 5PPI gives higher thermal performance (higher area goodness factor ratio) than 20 PPI. Also, decreasing porosity from 95% to 89% enhancement in the thermal performance was achieved. However, the metal foam heat exchanger that has a gap between metal foam and the chamber walls gave better thermal performance as compared with fully-filled foam heat exchanger.