ENHANCING ENERGY ACCESS BY EARTH-AIR HEAT EXCHANGER FOR BUILDINGS’ THERMAL COMFORT BY THE CONSTRUCTAL DESIGN

Abstract

Harnessing soil low-depth thermal energy to support mechanical systems for buildings’ thermal comfort has been considered one pathway for reducing the buildings’ energy demand (avoid) and adding renewable energy to buildings. The literature addressed those issues in many ways. However, this work introduces two key novelties: (1) the optimization of the duct’s configuration and (2) a strategy for the optimal use of the duct assembly to attend to the time-variable energy demand throughout the year. Both are based on the minimization of entropy generation. The irreversibility mechanisms relate to heat transfer and fluid flow in the EAHE and the coupled building-environment-soil-EAHE thermodynamic system. 

This approach was carried out by numerically solving the mathematical model (3-D, transient, heat-conduction finite volume with an upwind scheme and heat convection inside the ducts by known convective correlations) developed considering a solid parallelepiped domain on the ground (WLH), crossed parallel to its central horizontal axis by several channels of rectangular section (wLh), positioned in arrangements of variable geometry. 

The design degrees of freedom are the number of ducts, their dimensions, and the spacing among them while meeting prescribed thermal comfort temperatures for each season. Results show that if the energy access of the EAHE is enhanced or optimized for a date in the year, it may not be helpful in other seasons, thus showing that the greater access of the ground thermal energy throughout the year requires a compromise in the EAHE design.