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Optimization of Wind Louver Angle by CFD Simulation

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Optimization of Wind Louver Angle by CFD Simulation ARCHITECTURAL RESEARCH, Vol. 18, No. 4(December 2016). pp. 137-144 pISSN 1229-6163 eISSN 2383-5575 Optimization of Wind Louver Angle By CFD Simulation Gensong Piao, Donghwa Shon, Youngwoo Kim, Jungwon Lee and Jaepil Choi Researcher, Department of Architecture, Chungnam National University, Korea Researcher, Department of Architecture, Chungnam National University, Korea Ph. D candidate, Department of Architecture, Seoul National University, Korea Professor, Department of Architecture, Chungnam National University, Korea Professor, Department of Architecture, Seoul National University, Korea http://dx.doi.org/10.5659/AIKAR.2016.18.4.137 Abstract The objective of this study was to determine the optimal angle of a wind louver that would induce the optimal wind speed for indoor. Being controlled to have an optimized angle depending on the direction from which wind is blowing and the wind speed, the wind louver to be installed on the building envelop comes to create indoor comfort through a constant wind speed using the function that reduces the indoor wind speed by changing the angle when the wind speed is not lower than a certain level and makes wind flow into the room to the maximum when the wind direction is adverse to catching the wind or the wind speed is not higher than a certain level. To determine the optimal wind louver angle, a core-centered office building with cross-ventilation problems in the climate of Seoul, Korea, which experiences four distinct seasons, was considered for analysis in this study. A module 1 office space model was used for the CFD simulation to analyze the average indoor wind speed with respect to the outdoor wind speed (varied between 1 and 8 m/s), the wind louver angle, and the outdoor wind direction (varied between 0°and 180°in steps of 10°). Keywords: Wind, CFD, Wind Louver, Eco-friendly Architecture, Indoor Comfort 1. INTRODUCTION speed and direction over different seasons, an indirect method of natural ventilation based on temperature difference has been The comfort of a building is an environmental assessment developed more recently. criterion that significantly affects the quality of life or the It is considered that, if the challenges of natural ventilation can efficiency of the business conducted in it. This is because be overcome by using real-time control to achieve effective flow of the comfort felt directly impacts the human sensory system. the outdoor air current into a room, or to cut it off when need be, However, because the control of environmental factors such as the indoor air quality and comfort may be enhanced to reduce the light, temperature, and humidity is necessary for improving and cooling and heating energy consumption of the building.1 In the maintaining the comfort of a building, considerable amounts present study, we developed a system in which louvers are vertically of energy are expended on the required equipment. This has installed in the building1 envelop and controlled in real time with prompted the development of passive techniques for achieving regard to the wind conditions and the prevailing season.2 The indoor comfort and hence maximizing the energy efficiency of a system can be used to decrease or increase the indoor wind speed building. Such techniques include temperature regulation by solar by varying the angle of the louvers. We particularly investigated the energy, the stack–effect ventilation technique, and the storage of optimal angle of the wind louvers for achieving indoor comfort.3 heat in the walls or below a building. Natural ventilation, which When indoor air current speed exceeds a particular level, has been utilized from ancient times, is another very common discomfort may be experienced by the occupants. Moreover, in example. However, owing to the difficulty of controlling the wind the Korean climatic zone, there are three distinct seasons, namely, winter, summer, and spring/autumn, during which different indoor wind speeds are required for comfort. In the present study, Corresponding Author: Jaepil Choi the indoor wind speeds that are suitable for the different seasons Department of Architecture, Seoul National University, Seoul, Korea were identified, and CFD simulation and analysis were used to e-mail: [email protected] determine the angles of the wind louvers for achieving these speeds with respect to the outdoor wind speed. Based on the outdoor wind This research was supported by a Chungnam National University Grant in speed, wind direction, and angle of the wind louvers, 2,888 (19 × 19 2015. × 8) cases were simulated to determine the optimal average indoor wind speed. In addition, a function that can be applied to other This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. climatic zones was derived by an analysis of the correlation between org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, the outdoor and indoor wind speeds and the corresponding angle distribution, and reproduction in any medium, provided the original work is of the wind louvers for achieving indoor comfort in the Korean properly cited. climatic zone. ©Copyright 2016 Architectural Institute of Korea. 138 Gensong Piao, Donghwa Shon, Youngwoo Kim, Jungwon Lee and Jaepil Choi An example of a device that can be used to manipulate wind parameters for achieving indoor comfort by varying the speed flow into a room is the wind catcher, which was used in the of the wind blowing into the room through control of the angle ancient Persian region. The device is used to lower underground of louvers attached to the building envelop. The study was thus indoor temperature by catching the wind with a cross-shaped different from previous relevant studies.4 wall at the top of a tower-type building and making it flow into the underground. It is particularly suitable for areas with a hot 2. SIMULATION SETUP climate. In modern times, windows or forms of objet that receive wind have been used as wind catchers to improve ventilation The wind speed required to achieve indoor comfort in each performance under winds in specific directions. Moreover, while season relative to the outdoor wind speed in the Korean climate was several studies have been conducted on the use of louvers to established before the simulation. The 3D model and CFD analysis control solar radiation in buildings, rarely has the application of method were also established. the device to wind flow into a room been considered. Because the element that catches the wind is always fixed in such applications, the effect is maximized by moving the actual device based on the prevailing conditions. Figure 2. Simulation Model The outdoor wind speed range for the simulation was set to 1–8 Figure 1. Passive Cooling Using Wind Catchers (Legion in Persia) m/s, which had been determined by previous studies to be typical Source : http://www.customgreen.com.au for the Korean climatic zone. The annual mean values of the wind speed and wind direction were calculated for different heights, and In the field of architectural environment, CFD simulations based on the wind pressure at each height, could be adjusted using have been used to some extent in studies on buildings and wind. the ASHRAE (2001) standard. Generally, half of the average wind However, most of the studies considered natural ventilation speed for each season is recommended for use in the design of 5 methods such as cross-ventilation, as well as wind pressure and natural ventilation systems. However, in the case of Korea, which turbulence in a building or in an urban space. To the best of the has no outdoor wind speed standard for natural ventilation, the authors’ knowledge, no study has been found in which CFD wind speed data for Seoul with respect to the height, as corrected simulation was used to investigate the achievement of indoor by Jun et al. (2010), is used. In the present study, the wind speed for comfort through wind control. Through an experiment performed Seoul was calculated using the wind speed correction formula and on the effect of the window opening position and roof inclination meteorological data for between 1999 and 2008. By this means, angle on cross-ventilation, J. Peren et al. (2015) confirmed that the the wind speed at heights between 0 and 50 m was determined to roof inclination angle indeed affected the ventilation. H. Montazeri be 3.79 m/s, and that between 450 and 500 m was determined to et al. (2013) noted that many studies have focused on the effect of be 7.18 m/s. A wind speed range of 0–8 m/s was thus used for the 6 simple external building forms, whereas the balcony of a building present simulation. also affected the wind pressure and ventilation. T. Choi (2010) used The indoor average wind speed for human comfort with respect CFD to analyze natural ventilation by wind pressure in a high-rise to the temperature and climatic zone has been determined by building using a window that they developed, with the purpose different studies, and is available in international standards such as of determining the optimal indoor wind speed. Most previous ISO-7730 and ASHRAE. However, such standards, in addition to studies on louvers and wind were conducted by private companies being concerned with other environmental conditions, sometimes in the fields of machinery, and they mainly focused on the change conflict. In the present study, the climate was classified into three in the pressure or flow rate. For example, Komastu and Nakanishi seasons, namely, spring/autumn, summer, and winter, and the (2007) used CFD simulation and an experiment to establish the corresponding optimal indoor wind speeds were set to not more relationship between the shape of the louver on the front of a car than 0.5, 2.5, and 0.3 m/s, respectively, which are not significantly and the wind inflow and pressure.
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