Performance Evaluation of a Mixed Earth-Air Heat Exchanger

Resumo

Earth-Air Heat Exchangers (EAHE), also known as Ground-to-Air Heat Exchangers (GAHE), are sustainable and cost-effective systems designed to improve building energy efficiency by utilizing the thermal characteristics of the soil. The core principle behind EAHE is that the soil beneath the surface maintains a relatively constant temperature throughout the year, depending on the local climate and depth. This stability makes it an ideal medium for passive heat exchange, reducing the reliance on conventional heating and cooling systems. The system consists of underground pipes, arranged in horizontal or vertical configurations. During operation, air is drawn through these buried pipes, where it either gains heat from the warmer soil during winter or releases heat into the cooler soil during summer, effectively tempering the airflow before it enters the building. This process significantly reduces the energy needed for indoor climate control, leading to lower utility bills and a smaller environmental footprint. However, the performance of an EAHE depends heavily on the soil's hygrothermal properties, which influence heat and moisture transfer within the ground. Furthermore, in cold climates, the exchanger's performance can be increased by exposing part of the piping to solar radiation through a bypass. Furthermore, in cold climates, the exchanger's performance can be increased by exposing part of the piping to solar radiation through a bypass. To address this, a 2D model was developed to analyze the exchanger's performance. A modification in the tube circuit is proposed to take advantage of the effects of solar radiation on air heating. Experimental validation was performed through a prototype built at the Federal University of Technology of Paraná (UTFPR).