The influence of zonal air supply on thermal comfort in a classroom located in a hot and humid environment: a case study from Jeddah—Saudi Arabia

Abstract In hot and humid regions, many classrooms depend on air conditioning systems equipped with mixing ventilation to maintain acceptable indoor temperatures. However, this method often proves inadequate in delivering satisfactory thermal comfort due to elevated temperature and poor air distribution. This research explores the potential of zonal air supply strategies to enhance thermal comfort in a classroom situated in Jeddah, Saudi Arabia. During July 2024, field data—including measurements of airflow velocity, air temperature, relative humidity, and globe temperature—were collected to find key thermal comfort indices: Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD). In addition, a survey was administered to assess students’ thermal perceptions. Computational Fluid Dynamics (CFD) simulations were utilized to predict air temperature, velocity, and humidity distribution, evaluating the impact of zonal air supply designs on thermal comfort within the classroom. Parametric analysis was used to identify the most effective zonal air supply configuration for reducing PMV and PPD values. The findings show that, under existing ventilation conditions, PMV and PPD indices at different heights exceed the recommended limits established by ASHRAE Standard-55, indicating thermal discomfort during peak temperature periods. Further investigation demonstrated that introducing a 4-zonal air supply system could reduce PMV by 16–32% and PPD by 32–36%, thereby significantly improving thermal comfort in the classroom.