Bronze Wool as a Porous Mixer for Air Temperature Uniformity in Energy Exchangers

Abstract

This study investigates the use of bronze wool as a porous air mixer to improve temperature uniformity at the outlet of a liquid-to-air membrane energy exchanger (LAMEE). Traditional air mixers often cause excessive pressure losses and are difficult to install in compact systems. Bronze wool offers a lightweight, space-efficient alternative with favorable thermal and structural properties. Experimental evaluations were conducted using mixers with varying wool mass, porosity, and structure, under both horizontal and vertical duct orientations. Results show that bronze wool mixers significantly reduce temperature gradients, achieving up to 75% statistical effectiveness in horizontal ducts and 54% range effectiveness in vertical ducts. In compact wool structures, thermal conduction within the metal fibers is the primary temperature homogenization mechanism, while physical mixing from advection and dispersion occurs in higher-porosity structures. Among all configurations, the accordion wool structure demonstrated the highest range effectiveness, attributed to enhanced multi-directional conduction. The pressure drop across the mixers remained relatively low, confirming the suitability of metal wool air mixers for use in systems where minimizing flow resistance is critical. The findings demonstrate that bronze wool mixers provide a compact, low-resistance, and effective solution for temperature homogenization in air ducts.