Projeto: One of the current responses to the problems of rational use of energy in the housing sector may be provided by the use of Earth-Air Heat Exchangers (EAHEs). Among the air conditioning alternatives with the objective of replacing completely or partially electricity as a driver for thermal comfort, EAHEs stand as natural ways to improve the thermal conditions of built environments and reduce the conventional energy consumption. In general, an EAHE is a system of fans and buried ducts. The fans blow the outside air in the ducts where the fluid exchanges heat with the surrounding soil, then leaves the outlet at a milder temperature. This is due to the Earths thermal inertia: during the summer, the heat is stored by the soil which plays the role of an infinite thermal reservoir. As a result, the overall soil temperature turns out to be higher than the outside air in winter. The flow of air through pipes buried underground allows to preheat the fluid thanks to the heat exchanges soil-pipes. The reverse process occurs during winter times: day by day the overall soil temperature will decrease due to the heat released to the atmosphere, making the soil when the summer is here, a good thermal reservoir cooler than the inlet (atmospheric) air. The novelty of our approach lies in the global view developed through Constructal design. The Constructal law states that for a finite size flow system to persist in time (to live), its configuration must evolve in such a way that it provides greater and greater access to the currents that flow through it (Bejan, 1997, Bejan and Lorente, 2008). As such it governs the occurrence and evolution of any type of flow configuration in nature and engineering. The overall objective of the proposal is to envisage the underground networks that are used for EAHEs as evolving flow systems. We offer to design such flow architectures both at building scale and at district scale in the climatic context of tropical (Brazil) and continental (France) areas. The proposal is gathering research groups from Brazilian universities (UFPR in Curitiba, UFRGS in Porto Alegre, and FURG in Rio Grande), and two engineering (INSAT) and architecture (ENSAT) schools in France. The research will address the design of optimal EHAEs from heat and mass transfer perspectives together with the intertwined relationships between such networks whatever their scale, building-or district- and the groundwater flows. In addition, we will tackle the sustainable management of urban energy systems with technical issues related to the performance of these networks, typo -morphological problems related to architecture and urban planning, sociological issues related to the use and governance of these networks, and the adequacy of energy supply and users demand in the context of a sustainable city.

Resultados: This proposal will lead us to a complete description of the heat and mass transfer through the Earth-Air Heat Exchangers and the ground. From this basic analysis, we will contribute to improve the knowledge on the EAHEs design. With the help of the Constructal law of evolution and design, we will explore new EAHE configurations, dendritic, at building scale, which will be reflected through the proposition of design rules. We expect these new configurations to be dependent on the type of climatic conditions (tropical, continental). A better understanding of the impact of the network implementation on the ground water flow will allow to upscale our work to district EAHEs. Finally, one of the project outcomes will be network management rules based on sustainable energetic performances. From the track record of the history of collaboration between Professors Rocha, Errera, for the Brazilian side, and Lorente for the French side, we feel ready to start a more ambitious cooperation program involving our current PhD students. We believe that the research program that we aim to develop will also have impact on the starting career of our newly recruited young colleagues (Professors Ginestet and Labat at INSA, Professors Isoldi and Domingues dos Santos at FURG). Our research results will be published in peer-reviewed journals and presented in the top conferences of our field. In addition, we will organize an international conference towards the end of the program promoting the results obtained during the collaboration and contribution to a better dissemination of the results.