Design evaluation of Earth-Air Heat Exchangers with multiple ducts

Earth-Air Heat Exchangers (EAHE) are devices used to improve the thermal conditions inside built environments, which work by pumping the air through buried ducts to use the soil as heat source or sink. They explore the phase difference between the air and the ground temperatures, turning possible to heat the air in the winter or cool it in the summer. By means of Constructal Design strategies, this paper investigates geometrical configurations to assemble the ducts aiming to improve the thermal performance of their installations. This is done here by performing various computational simulations with different layouts to arrange up to five ducts, after imposing restrictions to the air flow and the installation volumes. The results show that significant improvements in EAHE efficiency can be obtained as follows: properly increasing the number of ducts and reducing their diameters, reducing, to some extent, the ratio between their vertical and horizontal spacing, and increasing the ratio between the installation volume and the computational domain. Therefore, the simple addition of ducts in EAHE installations does not mean a superior performance when no attention is paid towards how to arrange them. (C) 2018 Elsevier Ltd. All rights reserved.