Numerical Analysis to Understand the Influence of Ventilation Systems on the Thermal Comfort Parameters, Air Quality and Local Sweating

Indoor environments must maintain both thermal comfort and good air quality to support occupant health and wellbeing, making it essential to analyze airflow, temperature, and contaminant distribution together. This study presents a Computational Fluid Dynamics (CFD) investigation assessing multiple ventilation strategies in two office settings, an office cubicle and a conference room. The models include realistic indoor elements such as human occupants, furniture, computers, ceiling fans, and ventilation inlets and outlets. Ventilation scenarios were evaluated: full-capacity air-conditioning (AC), natural ventilation, ceiling fan with closed windows, ceiling fan with open windows, and a hybrid system combining fans with reduced-capacity AC. Simulations were performed in ANSYS Fluent and ANSYS CFX, with user-defined functions (UDFs) accounting for transient thermal loads and species transport. Key performance metrics included air temperature, velocity, CO₂ concentration, and mean age of air around occupants. A multiphase sweat-evaporation model was also applied to better capture localized thermal influence on the skin. The analysis shows that hybrid systems combining ceiling fans with reduced mechanical ventilation can maintain acceptable comfort and indoor air quality while substantially lowering energy consumption. Replacing high-tonnage, AC-only systems with hybrid systems using low-tonnage AC and ceiling fans reduces annual operating costs by more than 50%, with a comparable reduction in energy use under moderate outdoor humidity conditions (40–60%). These findings suggest that mixed ventilation provides a comfortable, cost-effective and energy-efficient alternative to full AC operation in subtropical climates such as Bengaluru, India.