Ceiling-Fan-Integrated Air Conditioning (CFIAC): Age-of-air, Air Pollution, and Airflow Distribution

¹ Division of Environment and Sustainability, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
² Center for the Built Environment, University of California, Berkeley, CA, USA.
³ School of Infrastructure Engineering, Nanchang University, Nanchang, China.
⁴ College of Civil Engineering, Hunan University, Changsha, China.
⁵ Department of Mathematics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
⁶ Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.

^* Corresponding author: chenwenhua14@tju.edu.cn

Abstract

Ceiling-Fan-Integrated-Air Conditioning (CFIAC) is a heating ventilation and air conditioning (HVAC) design approach that jets supply air into the vicinity of ceiling fans to be mixed and distributed within the room. This eliminates terminal ductwork and diffusers and provides very efficient cooling for the occupants. Two previously published papers have described the air velocity, temperature, and thermal comfort fields in a space conditioned by CFIAC. This paper is the third in this series, to evaluate CFIAC ventilation effectiveness and its effect on air pollution. In a test chamber, HVAC supply air was jetted from a high-sidewall vent into the centreline of a ceiling fan. The ceiling fan was operated at various conditions (off, level 2-downward, level 4-downward, and blowing upward). Carbon dioxide (CO2) was used as a tracer gas for the age-of-air evaluation, and as a proxy for an indoor air pollutant. For the age-of-air measurement, the CO2 source was injected into the side wall jet, and the age-of-air was monitored in various locations in the chamber. For the air pollution test, CO2 as the pollution source was released near a thermal manikin’s nose that was located in the middle of the chamber. The CO2 concentrations were measured at different locations around the ceiling fan and the thermal manikin. The ventilation effectiveness and health exposure are represented by the age-of-air and intake fraction (IF). At level 2 and level 4 downward fan operations, the age-of-air is reduced in the measured locations compared to the fan-off operation. The age-of-air for upward fan operation is equal to the age-of-air in fan-off operation, except for one location that is farthest from the fan. The IF results are very similar among all 4 fan operations, with level-4-downward and upward-fan operations slightly lower than the fan level-2 downward and fan-off operations. The study is considered preliminary, but at this point, we can say that fans reduce age-of-air and cross-infection risk.