Maximizing Efficiency of Earth-Air Heat Exchangers with Galvanized Blocks

Abstract

Earth-air heat exchangers (EAHE) consist of buried ducts and a ventilation system, which require minimal electricity, making them a cost-effective and sustainable solution for improving the thermal conditions of built environments. To enhance the efficiency of the EAHE system and optimize its use of the soil's thermal potential, we employed a galvanized block with a cross-sectional area of 1.5 m2 around the duct. The simulations conducted in this study used climatic data from Viamão, a city in southern Brazil, and demonstrated the effectiveness of this strategy. The galvanized block increased the thermal conductivity of the soil region and enabled the EAHE system to utilize higher quantities of thermal energy. The first part of the work highlights the importance of block coupling in improving thermal efficiency and the two potentials of EAHE systems. We also introduce a new method for calculating EAHE efficiency throughout the year. We name it maximum efficiency because it measures how much thermal potential an EAHE installation can extract from the highest amount available in the soil during the year. Subsequently, we conducted simulations of ducts at different depths to evaluate their performance. Our results showed that annual efficiencies increased significantly with the addition of the galvanized block. We also found how the installation depth impacts the thermal potentials. Specifically, we obtained almost 4.0°C and 3.8°C for the (annual RMS) soil and EAHE thermal potentials, respectively, at 3.5m.