Air Diffuser for Ventilation and Air Conditioning Systems with Quantitative Control

Abstract

AbstractThis paper proposes a new design of the variable geometry air diffuser for energy-efficient ventilation and air conditioning systems with variable airflow. The device enables to adjust the outflow parameters, and therefore the jet properties (range, expansion angle, decay rate). The kinematic characteristics of the formed jet are studied for different ratios of the inlet and outlet diameters of the air diffuser. In the course of the experiments, the jet axis velocities were registered at different distances from the outflow plane. It was shown that at the jet formation section (x ≤ 0.25 m), the axial velocity first decreases and then increases intensively, which indicates the presence of a rarefaction zone behind the baffle. It was found that the change in the relative jet velocity as a function of the distance to the air diffuser is practically the same for all the considered outflow velocities at a fixed angle of the case petals’ expansion. The change in the velocity coefficient with an increase in the expansion angle of the air diffuser plates was plotted. It was found that for small expansion angles the kinematic coefficient equaled 5.1, which is typical for a compact jet. At angles of 45° and 80° it equaled 3.9 and 2.9, respectively, which is typical for conical and fan jets. Thus, the proposed air diffuser allows adjusting the parameters of the outflow and, accordingly, the kinematic coefficient in a wide range, and can be used for ventilation and air conditioning systems with variable air supply.KeywordsVariable geometry air diffuserJetKinematicCharacteristicsAxial velocityChange in the velocity coefficient