Experimental investigation of different nozzle designs inside active chilled beams

The aim of this study is to improve the performance of active chilled beams (ACB) by varying the nozzles cross section geometry. Most of the common ACB today have circular nozzles for the primary air plenum, as they are easy to produce and ensure a good performance. The amount of induced secondary air and thereby the performance of the system can be increased by improving the properties of the primary air jet. In other research fields like engine jets or air diffusers, different nozzle designs have been developed to enhance the jets mixing. In this study, a generic test bench is built to investigate different nozzle designs for ACB. The flow field is investigated with particle image velocimetry (PIV) which gives detailed information about the jet’s shape. The designed test bench ensures optical access to the flow field while the induced room air is measured via differential pressure methods. The cross-shaped nozzle achieved the best results among the investigated ones and could significantly increase the induced air amount. An elliptic opening also shows promising results but cannot reach the performance of the circular nozzle in this study. A rectangular nozzle opening turns out to be unsuitable in ACB.