Estudo analítico-numérico e geométrico de estruturas galvanizadas para trocadores de calor solo-ar

Abstract

Earth-Air Heat Exchangers (EAHEs) are devices that assist air conditioning systems, contributing to the improvement of the thermal condition of indoor air in buildings while reducing electricity consumption. EAHEs operate using ducts buried in the ground and a low-energy-consumption ventilation system, causing the air to flow through the ducts and exchange heat with the soil, arriving at the buildings either cooled or heated, depending on the time of year. In this study, in addition to the conventional EAHE, a galvanized material is incorporated around the duct. This material, due to its high thermal conductivity, can take advantage of a large portion of the soil’s thermal potential. Thus, the objective of this work is to analyze the effect of the geometric configuration of galvanized structures in EAHEs to investigate the overall performance of the system. To achieve this purpose, an analytical-numerical approach was developed. The EAHE model is developed analytically, while the soil temperature is estimated numerically in two dimensions using the finite element method. The modifications in the dimensions and shapes of the galvanized material occurred in two stages: the first consisted of a parametric evaluation of five predefined material configurations to find the appropriate geometry and parameters that lead to the best system performance. The second stage used the Constructal Design method to find an optimized geometry to maximize system performance. As results, it is observed that the insertion of the galvanized material in the region near the EAHE duct was beneficial, as the system’s annual efficiency increased by approximately 20% compared to simulations without any type of structure. Furthermore, larger areas covered by the galvanized material do not necessarily translate into better thermal potentials for the EAHE or a better utilization of the soil’s thermal potential. It is also found that greater depths are not directly linked to higher thermal potentials. Moreover, it is highlighted that the highest levels of thermal potential were recorded in the approach using the Constructal Design method.