A Study On Airflow Characteristics Of The Dual-jet Air Curtain

In this paper, the airflow characteristic was studied with the dual-jet air curtain. Air curtain was often used as dynamic barriers to separate two different environments. In the heating and air conditioning building, the doorway air curtain could reduce energy consumption by preventing or decreasing the heat and mass transfer between indoor zone and outdoor environment. Traditionally air curtain had only a single jet. In order to improve its effectiveness, the dual-jet air curtain was proposed and researched.There were two ways to research the dual-jet air curtain. At first a stream function method was applied for analyzing the dual-jet air curtain's flow field. Secondly, the physical and mathematic models were established and the CFD technique was used to discuss the dual-jet air curtain's flow characteristics and their influence factors.Some conclusions could be found after the research. The dual-jet air curtain could be divided into two regions: convergence region and association development region. The convergence region's length was nearly proportional to the spacing of jets. The wider the spacing was, the longer the length was. When the jet entered the association development section, the single-jet's centerline velocity was bigger than dual-jet', but the jet extended width was narrower. The air curtains'ability to resist lateral pressure was related with jet velocity. The bigger the jet velocity was, the better the effect of the dual-jet was. Within design jet velocity, the dual-jet's dynamics characteristic would be better than single-jet'on the same conditions, and became better with the spacing increasing. The dynamics characteristic with the wider outlet is superior to the narrower one with the same jet exit momentum. The dual-jet's efficiency was also related to the pressure distribution. There were two distribution types: higher from the up to down, uniform distribution. The dual-jet air curtain was more effective for the former. As to the jet angle, it's about 45 to improve the effect for the dual-jet air curtain.By analysis, the mechanism was known why the dual jet air curtain had a better effect than the single jet. There were a double of stable backflow vortex and a low pressure zone on the convergence region of the dual-jet air curtain. And then two jets formed broader curtain. At the same time, the jets extended width was wider on the association development region.