Low Energy Comfort With Air Movement In Hot-humid Environments

Compressor cooling in buildings is already the main contributor to peak load in longtropical or sub-tropical summers, affecting both energy use and electrical grid safety, and thistrend is going to accelerate in the coming decades with the cooling demand growth in SouthChina, mainly due to the great population and booming economy in this area. In the face ofthe huge energy impacts that this increase is causing, one must examine alternative ways ofachieving comfort in warm-humid environments. Although air movement has been known asan effective to conserve energy while maintaining occupants’ comfort in warm-humidenvironments, only few studies have been done to address this topic. The aim of the currentstudy is to evaluate human responses to air movement in warm and humid environments.Firstly, in a well-controlled climatic chamber, human subjects tests were conducted oncomfort with personally controlled air movment in warm-humid environment. It was foundthat comfort upper limit can be extended to28°C/80%RH and30°C/60%RH. Thecomparions with the comfort zone with occupant control over air movement that specified byAmerican Society of Heating, Refrigirating and Air-conditioning Engineers (ASHRAE)standard55specified show big discrepancy. Based on our results, suggestions were made onrevising the standard to extend the allowable temperature and humidity limit.Secondly, an experimental study was conducted on subjective response to uncontrolledair movement from ceiling fans in warm-humid environments. Compare to the controlconditions without air movement, elevated air speed without occupant control were found tosignicantly increase the thermal comfort and perceived air quality (PAQ) up to30°C/80%RH,without causing discomfort due to humidity, air movement, eye-dryness and noise.Comparisons with ASHRAE standard55comfort zone without occupant control over airmovment show great discrepancy as well. It is suggested ASHRAE recommendation on airmovement should be revised to allow air speed to1.6m/s to improve comfort and save energy.Thirdly, experimental studies were done to address the effect of constant airflow andfluctuate airflow (sine wave change with a period of240s), direction of airflow and fix fan vs.oscillating fan on subjective responses in warm environments. It was found that constantairflow and fluctuate airflow can significantly impove thermal comfort and PAQ in warm-humid environment, although the differences between the two were not significantly different.Directions of airflow were found have no signicant effect on subjective comfort. At the samefan level. fix fan performed better than oscillating fan, however both mode were able toimpove comfort signifantly compared to the control condition without air movement. Finally, based the previous experiments, we conducted a correlation study on therelationships of subjective votes with thermal indices such as Predicted Mean Votes (PMV)and Standard Effective Temperature (SET), and the relationships among different subjectivevotes for three senarios–uniform thermal envrionments without elevated air movement, non-uniform conditions with elevated air movment with and without occupant control. PMV andSET were found to correlated with thermal sensation votes in uniform environment but notnon-uniform environment. Thermal sensation votes were found to a suitable subjective indicein uniform envrionments, but not non-uniform environment. Thermal comfort votes werefound to be the right indice to be used in all three senarios. An evaluation system was madebased thermal comfort votes.The results found in the current study can be used to guide the building design withelevated air movement for cooling in hot and humid climate.