Experimental and numerical study of the effect of perimeter jet enhancement on the capture velocity of a rectangular exhaust hood. (January 2021)

• Record Type: Journal Article
• Authors: Zhang, Jing; Wang, Jian; Gao, Jun; Xie, Mengxiao; Cao, Changsheng; Lv, Lipeng; Zeng, Lingjie
• Is Part Of: Journal of building engineering. Volume 33(2021)
• Publication Date: 2021-01
• Subjects: Centerline velocity -- Rectangular exhaust hood -- Jet -- Local ventilation -- Energy saving; Building -- Periodicals; 690.05
• DOI: 10.1016/j.jobe.2020.101652
• Languages: English
• ISSNs: 2352-7102

Abstract

Abstract: Using a radial jet at the outer edge of a circular exhaust hood can effectively reduce the velocity attenuation in front of the exhaust hood. The velocity distribution, especially the centerline velocity, is a key parameter in the effective design and use of an exhaust hood. In this paper, based on the derivation of the prediction formula of the suction velocity, the study of the suction velocity of jet-enhanced rectangular exhaust hood that considers the jet enhanced, viscous and geometrical effects is presented via the experimental and numerical methods. To understand the suction velocity distribution, the centerline velocity is investigated by varying the jet velocity, jet angle, jet slot width, exhaust rate and aspect ratio of the hood. It is found that the critical jet velocity condition is a most effective and energy-saving working condition for this kind of hood. Based on the critical jet velocity working condition, reducing the jet angle instead of increasing the exhaust rate is an airflow-rate-saving way to further increase the centerline velocity at a relatively large distance away from the hood opening. Calculation equations for the prediction of the centerline velocity of rectangular jet-enhanced exhaust hood are proposed. The error of the formula is proven to be within 10%, and its application range is proposed. The outcome of this work can help to efficiently design and use this type of energy-saving exhaust hood in residential and industrial local ventilation applications. Highlights: The suction velocity of the novel jet-enhanced rectangular exhaust hood is studied. The effect of the jet and aspect ratio on the separated flow at inlet is studied. The suction-velocity study considers the viscous, jet and geometrical effects. Determined the effective working conditions of this kind of exhaust hood. The formulas are recommended to predict the jet-enhanced suction velocity.