Experimental and numerical investigation of porous heat exchangers with Kelvin cell structured foam at high temperatures: Coupled conduction-convection and radiation heat transfer

Heat recovery is crucial in the energy sector, especially for industries operating at high temperatures. One way to achieve high-efficiency heat recovery is to use porous materials in heat exchangers. In this work, the performance of a high temperature heat exchanger was investigated. For this purpose, a tube containing a porous cast iron structure was externally heated by radiation inside a tubular furnace and air at ambient temperature was blown into the tube. Experiments were conducted at different temperatures of up to and different airflow velocities in a specialized bench, considering the combined effects of conduction, convection, and radiation. Temperature profiles in three sections of the porous structure were measured by using sheathed thermocouples brazed to the porous structure. Power and exergy flow rate extracted from the porous structure to the air flow were calculated and analyzed to quantify recovered heat. In addition, a numerical modeling performed at the pore level using Fluent showed an average relative error of 15% compared to experimental results, indicating acceptable agreement with observed trends. This numerical model will serve as a valuable reference tool for future parametric analyses of porous structures in heat exchanger configurations.