Improving the performances of earth air heat exchangers through Constructal design

Abstract

Summary Earth to air heat exchanger (EAHE) is a well‐known technique used to preheat or precool outdoor air before blowing it into a building. However, its geometry is often very simple as it consists in one or multiple straight pipes, while more complex arrangements can be found in heat exchangers design. In this paper, we explore the advantage of designing an EAHE as a network through the Constructal law point of view. A methodology is first proposed to design a single pipe EAHE when the need is defined in terms of cooling power, overall efficiency and enthalpy difference between the inlet air and the ground. Next, the single pipe EAHE is used as a reference for designing a tree‐shaped network under the constraint of identical fluid volume and cooling power. The geometrical features are allowed to change for the different branches of the network. The network coefficient of performance is found to increase significantly with the bifurcation level, illustrating the superior performances of the network. This approach was found to be robust as the improvements were not depending on the cooling demand or the environmental conditions. However, further work is needed to move from this theoretical result to practical considerations.

Numerical humidity assessment: analysis of the thermal performance of a residential building

“…Studies developed in recent years have shown high thermal potential for EAHE installations (Vaz, 2011;Vaz et al 2011Vaz et al , 2014, also estimated by models developed in Brum (2013); Brum et al (2012Brum et al ( , 2013. Aims of recent study have included analyzing its construction parameters (Brum et al, 2016); and improving its performance utilizing numerous pipes (Rodrigues et al, 2015;Brum, 2016;Brum et al, 2017Brum et al, , 2019b; Brum, Labat and Lorente (2019a). Work carried out by Estrada et al (2018) presents the efficiency of EAHEs in several regions of Brazil, demonstrating that tropical climates are also a good option for installing EAHEs.…”