Dynamic Airflow Patterns and Directional Effects on Human Thermal Comfort: Evidence From a Controlled Chamber Study

Abstract

Despite growing interest in airflow-based cooling, the combined effects of airflow mode and discharge angle on human thermal comfort remain systematically unexplored, particularly under hot–humid conditions. This study presents a controlled chamber investigation that jointly examines airflow mode and discharge angle within a unified experimental framework, directly comparing fan-assisted ventilation against still-air and actively cooled baselines. Twenty-six participants were exposed to constant, sinusoidal, intermittent, and oscillating airflow patterns at discharge angles of 45°, 65°, and 90° under three environmental conditions: air-conditioned (AC), mechanically ventilated (MV), and a warm still-air control group (CG). Subjective responses—thermal sensation vote (TSV), thermal preference, thermal acceptability, and thermal satisfaction—were collected and compared against objective predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) metrics. Results showed that air-conditioning yielded the highest thermal satisfaction, while mechanical ventilation improved airflow perception without a commensurate gain in overall comfort. Within the AC condition, the 65° discharge angle combined with oscillating airflow was associated with relatively higher satisfaction responses, whereas 90° horizontal airflow provided more uniform but less preferred cooling. Dynamic airflow patterns influenced TSV but did not reliably enhance overall satisfaction across all configurations. Notably, PMV and PPD showed limited agreement with subjective satisfaction, acceptability, and airflow preference under dynamic ventilation, despite moderate-to-strong correlation with TSV. This suggests that steady-state models have limitations in capturing integrative comfort responses in nonuniform airflow environments. Airflow angle and temperature preference were stronger predictors of comfort than fan speed or airflow mode alone. These findings support the integration of directional, low-frequency dynamic airflow into adaptive, energy-efficient ventilation design.