An Active Diffuser Control Method Based on the Constant Jet Throw for Improving Airflow Distribution in Variable Air Volume Systems

The air supply of the variable air volume (VAV) system could decrease with indoor load, resulting in reduced indoor comfort. An active diffuser is a good solution, but its adjustment process is often neglected. In most cases, the diffuser maintains the air supply velocity constant by controlling the air supply area. This traditional control method based on constant velocity (CMV) often fails to reach jet throw expectation due to the continuous change of airflow diffusion performance during the adjustment process. In this study, a new control method based on constant jet throw length (CMT) is proposed and applied in two typical rooms (office and conference). The results show that the CMT could increase the throw length in the spreading zone and enhances the airflow at the wall zone and ground zone, providing a more uniform temperature and more comfortable indoor environment. In 40% air volume condition, the air diffusion performance index (ADPI) in the office using CMT has improved from 89.66% to 95.69% compared to CMV, while ADPI in the conference improved from 92.11% to 97.37%. This study can help designers determine the optimal adjustment scheme to improve the adaptability of the active diffuser to the VAV system.