Performance analysis of air-to-ground heat exchanger in equatorial Yaoundé: Hourly and daily thermal behaviour and efficiency optimization

Abstract

This study examines an air-to-ground heat exchanger operating continuously during Yaoundé’s hottest month. The paper focuses on identifying cooling and heating periods based on the local thermal comfort range. We equally determine the duct length needed for 70 % efficiency at various air inlet speeds. Ground temperature measurements are taken to inform an analytical model predicting air outlet temperatures. Additionally, calculations are made for hourly thermal efficiency and potential. The results reveal ground temperatures ranging from 20.8 °C to 23.4 °C within 5 m of the surface. To achieve 70 % efficiency, duct lengths range from 44.3m to 48.7m depending on air inlet speed (0.5–1.5 m/s). The air-to-ground heat exchanger system can effectively cool buildings between 8am and 10pm, delivering comfortable air temperatures (23.5–25.5 °C). The air-to-ground heat exchanger can also provide heating from midnight to 5am before switching to cooling for the rest of the day. This demonstrates the potential of air-to-ground heat exchanger systems in equatorial climates to maintain comfortable indoor temperatures throughout the day by both heating and cooling buildings. The study's implications suggest that AGHEs can significantly enhance energy efficiency in building systems in equatorial regions, offering a sustainable solution for climate control. The novelty of this research lies in its detailed analysis of AGHE performance in a specific equatorial climate, addressing previously unexplored aspects of hourly and daily thermal behaviors, and providing valuable insights for optimizing AGHE systems in similar climates.