Evaluation of Air Diffusion Performance and Thermal Environment by Additional Vanes of Ceiling-mounted Air Conditioner

Ceiling-mounted air conditioners often cause thermal discomfort when the discharged cold air descends directly to the occupied zone, generating a cold draught for occupants.To prevent the local discomfort, guide vanes are commonly installed to deflect the air flow from the ceiling-mounted air conditioner; however, the effect of additional vanes on the air diffusion performance and thermal environment has not been investigated in previous studies.In this study, a length-adjustable vane was developed to adjust the air flow passing through the vane.The impacts of the vane on the air diffusion performance and thermal environment were evaluated in a university lecture room located in the Busan region.The field test results showed that the vane was effective in reducing the air velocity and elevating the air temperature in the occupied zone, whereas the stretched vane was ineffective in mitigating the air velocity in the zone.The air diffusion performance index (ADPI) was not degraded by applying additional vanes.The application of the vanes resulted in the slight enhancement of ADPI from 79.6% to 80.4%, satisfying the ASHRAE standard for room air diffusion.In addition, the vanes were effective in achieving thermal comfort near the neutral state.The predicted mean vote (PMV) of the occupied zone met the thermal comfort category A or B of the ISO 7730 standard.The developed vanes effectively improved the air temperature and velocity distribution, ADPI, and PMV.Further study is suggested to investigate the impact of additional vanes under various cooling loads and operating conditions (e.g., supply air flow rate, temperature) of air conditioners.