Active Chilled Beam Wall Jet Prediction by the Free Convection Model

Abstract

In this study, the measured and predicted air distribution of an active chilled beam in a typical office room is described. A free convection model was applied for the vertical downward air jet along the wall by superposing a free convection velocity and an isothermal jet velocity. The velocity and temperature of the wall jet were measured at six different heights and six distances from the wall in the near wall zone and in the wall-floor corner zone. The experiment implemented two airflow rates of 20 and 28 L/s with three cooling loads of 0, 40 and 100 W/m2. The results of the measurements show that the maximum velocities were close to the wall surface, between 0.025 to 0.05 m from the wall. Below the height of 1.7 m, air velocities decreased quasi-linearly when approaching the floor level. The calculated non-isothermal wall jet velocities superposed with the free convection velocity show that the introduced model can be used for the prediction of the maximum velocity of the wall jet. The model is free of a problem of the conventional non-isothermal jet equation, which predicts velocities slightly increasing downwards, while the measured ones significantly decreased along the wall.