Field Evaluation of Thermal Comfort and Cooling Performance of Underfloor Air Distribution Systems in Stratified Spaces

Indoor environments have received increasing attention in recent years, and achieving high-quality indoor conditions has become increasingly important. Underfloor air distribution (UFAD) systems have attracted significant interest due to their potential to improve ventilation efficiency, enhance thermal comfort, and reduce energy consumption. Compared with overhead air distribution (OHAD) systems, UFAD not only offers better energy savings but also demonstrates improved thermal stratification performance. However, most previous studies have relied on numerical simulations to evaluate UFAD performance under specific system designs or scenarios. Few studies have conducted on-site measurements to investigate the combined effects of multiple air-conditioning settings, which are closely related to user control strategies. This study experimentally evaluated the cooling performance and thermal comfort of a UFAD system under different control configurations. By combining variations in airflow rate, temperature setpoints, and supply air distribution, a total of 12 test configurations were examined. The results indicate that configurations with lower temperature setpoints achieved the highest cooling performance. Most test settings produced neutral thermal conditions at heights between 120 and 180 cm, while areas at 60 cm or below were noticeably cooler. These findings provide practical guidance for users in controlling UFAD systems.