NUMERICAL-EXPERIMENTAL ANALYSIS OF THE PERFORMANCE OF AN EARTH-AIR HEAT EXCHANGER (EAHE)

Resumo

Studies have been searching for new ways to lower energy demand in air conditioning conditions
because heating and cooling make up a sizeable component of global energy consumption. As a result, discussions
about building energy efficiency and the active and passive solutions needed in thermally inefficient design
projects have increased in recent years. Soil may be used as a renewable energy source, and the employment of
passive solutions in these projects has proven beneficial for energy savings. Due to its high thermal capacity, the
soil can act as a large thermal reservoir, largely independent of the climatic conditions of the surfaces, adding or
removing heat from the ambient air inside the buildings. This study investigates the effectiveness of an earth-air
heat exchanger (EAHE) in heating or cooling air in various environments. The system, which includes 100 mm
diameter Polyvinyl Chloride (PVC) ducts, 2" galvanized steel pipes, and a fan for airflow control, was built on the
premises of the Federal University of Technology of Paraná (UTFPR) Campus Ponta Grossa. The pipes were
insulated to prevent heat loss along the way, and a series of k-type thermocouples were inserted along the EAHE,
the ground, and the environment. Temperatures were recorded hourly over four days in January 2022 using a data
acquisition system. From the data of the experiment, a numerical analysis was performed to evaluate the
temperature variation, heat removed, and to calculate the coefficient of performance of the heat exchanger and
compared with the experimental results. Despite the thermal gains of radiation in the system and in the ground,
the consequent increase in the inlet temperature of the exchanger, and the relatively low COP, positive results were
obtained in the removal of heat from the environment, factors such as the high power of the fan and the climate in
the region were crucial to ensuring that results did not improve.