The earth-air heat exchangers (EAHEs) are devices that are shown to be a great alternative to assist in the thermal comfort of buildings, mainly due to their low energy cost. The proposed model considers the heat exchange between the soil, the duct and the air, generating coupled equations. This work seeks to employ and verify EAHE applications in two scenarios, first in a literature experiment and then in a EAHE application in Pelotas. In both scenarios, it is considered that the soil and air temperature functions are time dependent. The solution is obtained by applying the Laplace transform and for the inversion of the integral transform the numerical method known as the Gaver-Stehfest Algorithm was used. The obtained results show that the proposed model follows the behavior of the experimental data. In addition to the experimental data, the proposed model was compared with the analytical model by Nóbrega, where the results had a small variation (of 0.20 ºC between them) by considering the heat transfer process in the duct material, modeling a more close to the real situation.

This study evaluates the impact of integrating Phase Change Materials (PCMs) in the efficiency of Ground-Air Heat Exchangers (GAHEs). A three-dimensional computational model for the GAHE system with an integrated annular PCM (GAHE-PCM) was implemented in ANSYS Fluent using the Finite Volume Method, accounting for the meteorological conditions and ground properties of Viamão, Brazil. A parametric evaluation with fifteen rectangular and fifteen elliptical PCM container configurations were analyzed by varying their geometric ratios. Results indicate that the inclusion of PCM may enhance the yearly thermal potential as high as 69.31% in heating and 27.92% in cooling. Geometries, such as square or circular cross-sections, maximize heat exchange with the airflow, whereas elongated shapes reduce PCM efficiency. Furthermore, placing most of the PCM in deeper, thermally stable soil layers reduces the overall performance. For near-optimal designs, the differences between rectangular and elliptical containers are minimal, providing flexibility for system implementation.

Earth-air heat exchangers (EAHE) represent a promising option to reduce theheating/cooling load of buildings. Unlike traditional air conditioning systems, the EAHE employ a renewable source of energy and they can work using low electric power. Basically, EAHE employ underground ducts where the air is blown to exchange heat with the ground. Since the superficial layers of the Earth are warmer than outside air in winter and cooler than it in summer, the soil canbe used as a heat source or sink. Therefore, the air leaves the ducts at milder temperatures. Recent research has shown that the Brazilian south region, where prevails a subtropical climate, has a high potential for the use of EAHE. However, such references are still very limited. Hence, this work aims to analyze the thermal performance of EAHE considering the city of Pelotas, located in the south Brazilian state of Rio Grande do Sul. As a case study, we used in situ data, covering thesoil geotechnical profiles from a site in the city, which were obtained by a standard penetration test (SPT). To make the computer simulations, we used an analytical model, which was previously tested and validated. The results point out good prospects for the installation of these devices in the city of Pelotas, taking advantage of its geological potential

A humanidade tem buscado alternativas aos mais diversos sistemas que utiliza no seu dia, visando alcançar uma convivência mais sustentável com o planeta. Entre tais sistemas, destacam-se os aparelhos e sistemas empregados a fim de atender às demandas de conforto térmico de ambientes internos de edificações, como residências, comércios, hospitais. Os trocadores de calor solo-ar (TCSA) constituem uma opção a ser levada em consideração nesse quesito. Neste trabalho, desenvolve-se um modelo numérico baseado no método das Diferenças Finitas para determinar o potencial térmico de um TCSA composto por um só duto. O modelo é validado com os dados apresentados na literatura mais recente da área e empregado para avaliar o desempenho de um TCSA em uma metrópole no sul do Brasil. Os resultados apontam para a eficiência do sistema em Porto Alegre, destacando uma economia energética significativa decorrente de sua utilização.