Optimizing earth-to-air heat exchanger performance: thermal analysis and parametric optimization study using laboratory simulation and response surface methodology

Earth-to-Air Heat Exchanger (EAHE) systems present an extremely profitable addition to energy-efficient HVAC solutions in sustainable buildings yet optimizing their adaptability and performance remains a challenge. This study develops an EAHE system with optimized performance-to-cost characteristics, reduced energy demand, and reliable operation.

A mathematical model was developed in MATLAB and validated against experimental measurements of air temperature along the pipe under steady-state conditions, showing a maximum deviation of 2.55 $\%$. The system was tested under various pipe materials, burial depths, diameters, lengths, and inlet air conditions. This validated model was then used to generate a dataset for parametric analysis, which formed the basis for constructing a Response Surface Methodology (RSM) model. This approach allowed for optimization of system performance while reducing reliance on extensive physical testing. Key findings include minimal impact of pipe material on performance. Longer pipes improved heat transfer by 15 $\%$, while smaller diameters improved thermal efficiency by 12 % due to stronger convective effects, but also increased flow resistance. At the optimal conditions (inlet temperature of 45 °C, air velocity of 2.562 $m/s$, pipe diameter 0.0238 $m$, and length of 5.27 $m$) the system achieved 92 $\%$ thermal effectiveness and up to 25 $\%$ reduction in fan power consumption. This study delivers a validated simulation framework and an experimentally informed optimization strategy that supports the design of efficient EAHE systems for sustainable building applications. Future work may focus on field-scale implementation, integration with dynamic simulation tools CFD, TRNSYS, hybrid operation with active cooling systems, and full life-cycle cost assessment.