Findings of personalized ventilation studies in a hot and humid climate

The concept of personalized ventilation (PV) is at the cutting edge of technological development in the area of air conditioning and is fundamentally aimed at improving ventilation in the immediate breathing zones of occupants in the built environment. While the current state-of-the-art PV systems make this possible for seated individuals within the occupied zone, it is envisaged that flexible PV systems, extending the range of application within the dynamic movements of individuals in an air-conditioned zone, may be a reality in the near future. The ability of P V systems to enhance thermal comfort and indoor air quality (IAQ) and the energy savings that would result were examined under the hot and humid tropical conditions of Singapore. The experimental design consisted of 17 different environmental conditions, characterized by a combination of room ambient temperature (23 degrees C and 26 degrees C), PV air temperature (20 degrees C, 23 degrees C, and 26 degrees C), and the PV airflow rate (7, 11, and 15 L/s per person). The experimental design also included a reference condition with the primary background air-conditioning system operating under the same conditions but without PV air. Eleven human subjects took part in all the experiments, and a detailed questionnaire was employed to solicit their subjective responses during each exposure. Air velocity, air temperature, and ventilation effectiveness were measured in the immediate breathing zone of each occupant. The results indicate that the use of a secondary PV system in conjunction with a primary air-conditioning system not only enhances thermal comfort and IAQ acceptability but can reduce energy consumption by 15-30%. PV systems can improve ventilation effectiveness at the immediate breathing zone by up to 50% more than can be obtained with mixing ventilation (MV) alone, and P V tends to lower the average temperature of inhaled air in the breathing zone by 2-5 degrees C, enhancing perceived air quality. PV temperature and PV flow rate were found to be more critical than ambient temperature for occupants' thermal comfort and the perceived air quality of inhaled air.