Experimental investigation of different nozzle designs inside active chilled beams

Max Rohn,Paul Mathis,Dirk Müller,S.I Tanabe,H Zhang,C Inard,L Mazzarela,G Cao,M.C Gameiro Da Silva,P Wargocki,I Nastase,J Kurnitski

doi:10.1051/e3sconf/201911101005

Abstract

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.

Highlights

The use of active chilled beams (ACB) in modern HVAC systems is receiving more attention during the last past years
One major aspect is the reduction of the fresh air amount, which is proved in the studies of Mathis et al [1]
By installing the elliptic nozzle, the pressure loss is slightly decreased and the induction ratio (IR) decreases by 3.0 %

Summary

Introduction

The use of active chilled beams (ACB) in modern HVAC systems is receiving more attention during the last past years. Their significant advantages compared to typical all-air systems make them a promising opportunity regarding energy savings in the building sector. In allair systems the occurring heat loads are removed by supplying conditioned air, in the following called primary air, to the room. The ratio of induced room air and primary air is called induction ratio (IR). It is a suitable indicator for the performance of the system and its enhancement is one major goal when optimizing ACB. Smaller nozzle diameters and larger distances between the nozzles lead to an increase of the IR, whereas these changes lead to smaller volume flows, which is not always acceptable because of the humidity restrictions inside the room

Objectives

Methods

Results

Conclusion