Mixing characteristics and co-flow behavior in interactive cascade ventilation: An experimental approach

Abstract

Achieving optimal indoor air quality that is both healthy and comfortable remains a persistent pursuit. Interactive cascade ventilation (ICV) has demonstrated remarkable performance, harnessing a temperature gradient to reverse the direction of buoyancy flux. The aim of this study is to investigate the mixing characteristics and co-flow behavior of ICV. Experiments, informed by Abramovich's theory and the principles of similarity, are conducted using a scaled-down experimental setup. The research results indicate that varying the temperature difference between the upper and lower jets from 2 °C to 7 °C significantly influences the deflection angle. Notably, the lower jet exhibits a more pronounced decrease of 52 %, suggesting that the warmer lower jets effectively uplift the cooler upper jets. It can counteract their descent, optimizing the use of cool air in occupied spaces. Additionally, analysis of different velocity ratios reveals a reduction in the deflection angle from 12.69° to 5.57° as the velocity ratio increases from 0.5 to 0.81. A modified jet equation has been derived, which delineates the central path of the jet trajectory. The insights obtained from this research serve to bolster the theoretical framework for optimizing critical supply air parameters within the ICV system, thereby significantly enhancing its ventilation performance. These findings elucidate the underlying mechanisms of ICV, leading to a more profound understanding of its operational dynamics.