Active Chilled Beams for Producing Symmetric Air Discharge Patterns Using Jet-Cone System: an experimental study

Literature studies show that the efficiency of Active Chilled Beam (ACB) systems can be improved by proper modifications in the geometry of its terminal unit [1]. A typical ACB system comprises of a heat exchanger, primary air plenum, mixing chamber and set of nozzles, as shown in figure 1. Nozzles with different shapes and sizes, in the terminal part of ACB unit discharge air into the occupied zone [2]. A previous study shows that asymmetric flow with large-scale circulation patterns were produced by ACB units and can be a cause of draught discomfort for the building occupants [3]. The uneven air jet patterns have been observed from the nozzles inside the ACB discharge unit. The velocity differences between the nozzles, which are close to the ACB inlet and the ones, which are away from it cause these uneven air jets. Different design modifications have been applied to produce air velocities of equal magnitude from all nozzles. Uniform velocities were achieved either by using small size nozzles (9mm diameter), or by adding a board in the middle of the air plenum to have uniform discharge from the terminal unit [4]. Jet cone system [5], can provide uniformity and controls over supply airflow coming out of the terminal units into the room, compared to conventional nozzle designs applied for ACBs. The jet-cone system can change the magnitude of airflow rates and the air direction through different pin adjustments. This can reduce the risk of draught by providing uniform air distribution patterns in the occupied zones.