The Air Distribution Around Nozzles Based On Active Chilled Beam System

During the past two decades, the utilization of Active Chilled Beam (ACB) systems as promising air-conditioning systems has becoming increasingly prevalent in Europe, North America and Asia. However, the studies on air distribution of ACB systems are still inadequate. The air distribution has a great impact on thermal comfort. The ununiformity of air distribution will easily lead to turbulent flow which can cause unpleased feeling such as draught in the occupied zone. ACB terminal unit is the source of the air flow entering into the occupied place, which plays a crucial role on the air distribution inside the room. Therefore, it’s of great importance to evaluate the air distribution in the vicinity of ACB nozzles. In order to fulfil the gap, air distribution for a two-way discharge ACB terminal unit is investigated in this study. The air velocities around the nozzles under different conditions are tested in a 7.3m*3.3m*2.5m thermal isolated room and simulated by a three dimensional Computational Fluid Dynamics (CFD). After being verified, the CFD model is utilized to examine the effects of nozzle diameter and inlet pressure. From the results of experiments and simulation, it is found out that the air flow is discharged in an asymmetric way from nozzles, which is ascribed to un-uniformity of pressure distribution inside ACB caused by the layout of the duct. Moreover, the un-uniformity is significant when the nozzle diameter is large and the elevation of the inlet pressure would aggravate this ununiformity. Therefore, as we design the ACB systems, high attention on the nozzle diameter should be paid to prevent the un-uniformity air flow when the nozzles and the inlet pressure are large. Eventually, a proper strategy to solve this problem is also proposed and validated by CFD simulation.