A field study of occupant thermal comfort with radiant ceiling cooling and overhead air distribution system

Abstract

This paper presents the findings of a field research on occupant comfort with radiant ceiling cooling and overhead dedicated outdoor air system (RCF). This extends a previous thermal comfort study with radiant cooling and intended to investigate the actual occupant thermal comfort with radiant ceiling cooling and overhead air distribution system. The research is based on a revised ASHRAE RP-921 project protocol with a combination of field measurements and questionnaires. A total of 135 sets of data from 44 participants were collected in summer. The results show that occupant whole-body thermal sensations with the radiant ceiling and overhead air system had deviated from the PMV model at the 23.6~28.6 °C operative temperature (OPT) range in the summer. The main advantage of the RCF system for thermal comfort was found to be better comfort conditions than with conventional air conditioning at the same operative temperature range. The results of this study showed that the neutral temperature with the RCF is around 26 °C; the preferred temperature by occupants was around 25.3 °C with the RCF. The calculated Predicted Percentage Dissatisfied (PPD) rate is 13.9%, but the actual thermal environment dissatisfaction rate was 8.3% with an unacceptability rate of only 1.5%, which is substantially better than the calculated PPD rate. The study results were compared to earlier findings and validated against some important results, providing benchmarks for future work.