Análise de desempenho de trocadores de calor solo-ar aletados com materiais galvanizados

Abstract

Soil-to-air heat exchangers, EAHE, present themselves as an alternative technology to provide thermal energy using a renewable source; with them it is possible to cool the air in a building in the summer and heat it in the winter, taking advantage of the thermal inertia of the ground. The heating and cooling capacity of EAHE depends on factors such as the local climate, soil properties and installation configuration. This work aims to evaluate the thermal performance of EAHE introducing galvanized materials. The idea is to increase the heat exchange between the duct and the surrounding soil, as galvanized materials have a higher thermal conductivity than the soil. The thermal performance of EAHE is evaluated through their thermal potential and efficiency. The simulations for the development of this work use an analytical, one-dimensional, Graphische Auslegung von Erdwärme Austauscher-known (GAEA) model that calculates the air temperature in the EAHE duct by estimating heat transfer coefficients between the air, the duct wall and the soil, based on the thermophysical properties of the duct material, the flowing air and the surrounding soil. Soil temperature is calculated by solving the heat transfer problem in two dimensions through a combination of finite difference and finite element methods. The city of Viamão, in southern Brazil, was adopted as the physical context of this work, given that its climatic and soil conditions are accessible through publications referring to an experimental installation built there. The results show that the thermal potential of EAHE is improved by 33%, equipping the ducts with the galvanized block and fins, as well as its efficiency that reaches almost 95%. Using the same methodology, the performance of the EAHE was estimated varying the depth of the installation, obtaining results in line with recent literature, values close to 3 m are recommended. In addition, a study was carried out considering the increase in the thermal conductivity of the region around the duct and its effect on the performance of EAHE, resulting that such increase must be done in the direction of increasing depth.