Analysis of the factors influencing the airflow behavior in an impinging jet ventilation room
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Analysis of the factors influencing the airflow behavior in an impinging jet ventilation room
1. School of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China 2. School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou, 225127, China 3. School of Mechanical and Automobile Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
Abstract
Keywords
A validated CFD model is employed to predict the airflow behavior in an impinging jet ventilation (IJV) room with cool, isothermal or warm jets. By using the numerical results, the influences of jet discharge height, supply grille shape and room height on the jet flow behavior as well as the draught discomfort are analyzed for IJV operating in heating scenarios. The results indicate that the warm supply jet of IJV rises upward to the ceiling after spreading along the floor for a certain distance due to thermal buoyancy, resulting in a limited dispersion area, while the cool and isothermal jets of IJV always spread along the whole floor. When IJV is used for space heating, the lower the jet discharge height, the farther the supply air spreads along the floor, and the supply grille shape and room height almost have no effect on the air dispersion area. The results also show that the energy-efficient advantage of IJV in its heating mode compared to the mixing ventilation (MV) system is more remarkable in higher rooms. Moreover, there is a risk of draught discomfort in IJV heating rooms and it is recommended to wear socks to avoid this discomfort.
impinging jet ventilation,
1
Introduction
heating scenario, airflow behavior, draught discomfort
Article History Received: 01 July 2019 Revised: 06 July 2020 Accepted: 16 July 2020 © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020
One advantage of IJV is that it produces a clean air zone in the lower part of the occupied zone and exhibits higher air-exchange effectiveness than the MV system. Another advantage is that it can be used not only for room cooling but also for space heating, giving it greater working flexibility than the DV system. Moreover, the warm supply jet of IJV is directly delivered to the occupied zone unlike the MV system which cannot distribute the warm air into the lower parts of room effectively. Consequently, the IJV system has the potential to be an alternative to the DV and MV systems (Awbi 2003; Karimipanah and Awbi 2002). Although the biggest advantage of IJV is that it can meet the requirement not only of room heating but also of room cooling efficiently, most of the existing studies focus on the cooling or isothermal scenario. Only a few studies have been done to evaluate the ventilation performance of IJV operating in heating mode up to now. For example, Gauntner et al. (1970) reviewed the flow field of a single impinging jet and presented the methods for determining the pressure and velocity profiles in the IJV room. Beltaos
E-mail: [email protected] (Ke Zhong); ymkang@dhu.
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