Evaluation of thermal comfort and age of air on employing micro-zonal air-conditioning in an existing open-plan office in India

Abstract

Micro-Zonal Occupant-Centric Control (MZOCC) is an emerging strategy to facilitate localized air-conditioning within large thermal zones. While energy-saving potential of MZOCC is extensively studied, adequate studies have not explored its impact on thermal comfort. Localized air-conditioning can lead to discomfort due thermal gradients, draft, and poor ventilation. This study evaluates thermal comfort, air of age, and ventilation effectiveness in an Indian open-plan office, offering quantitative insights into the effects of MZOCC on thermal comfort. Results indicate that thermal comfort is achieved in micro-zones before reaching setpoint temperature and using setpoint-based control causes over-conditioning. PMV values near the diffusers fall below 0.5; while further away, they exceed 0.5. Percentage of people dissatisfied due draft exceeds 20% in most of the experimented scenarios. In few scenarios, temperature differences between head and ankle reach 5 °C, indicating discomfort from thermal gradients. Cool air jets from diffusers are concentrated at specific regions around the diffusers, causing discomfort from horizontal gradients. Though breathing level has relatively fresh air, air-conditioning the entire zone using only two cassette diffusers results in air stagnation. These findings underscore the difficulty in maintaining thermal comfort under localized cooling methods like MZOCC, suggesting the need for improved air distribution and airflow control.