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Shen H.,Xian Jiaotong University | He Q.,Shenzhen Institute of Building Research | Huang Y.,Xian Jiaotong University | Liu Y.,Xian Jiaotong University
Lecture Notes in Electrical Engineering

With the expansion of city, more and more tall buildings arise. It is very important to understand the wind field around buildings for creating safe and comfortable wind environment. At present, three kinds of methods can be used to obtain the wind field information around tall buildings. They are wind tunnel experiment, wind field measurement, and numerical simulation. Numerical simulation is the cheapest way, in which Reynolds averaged Navier-Stokes equations and large eddy simulation approaches are commonly used to simulate turbulent flow. To ensure the accuracy and reliability of the two approaches, the solution validation studies are needed. In this paper, Shear Stress Transport (SST) k - ω model has been used in solving Reynolds averaged Navier-Stokes equations (RANS) and kinetic-energy transport subgrid model has been employed in large eddy simulation (LES) in the simulation of the flow field around a square column. Comparing the numerical results with experimental data, the characteristics of the two models are revealed and their reliability is analyzed. The results show that both kinetic-energy transport model in LES and SST k - ω model in RANS can be used to simulate the field around building but the results are different. With kinetic-energy transport model in LES, the vortex generation and a group of high vertex zones are observed. © Springer-Verlag Berlin Heidelberg 2014. Source

Huang Y.,Xian Jiaotong University | He Q.,Shenzhen Institute of Building Research | Shen H.,Xian Jiaotong University | Liu Y.,Xian Jiaotong University
Lecture Notes in Electrical Engineering

Ground pollutants such as SO2, CO, and other gaseous pollutants generated by the traffic always harm the environment of urban residence communities. Fences or enclosures are common for residence communities in China for security reasons, while they really hinder the wind flow and the pollutant diffusion. In this paper, the computational fluid dynamic (CFD) method has been used to simulate how the fence affects the diffusion of the traffic pollutants around a building. The k-ε equation is used to simulate the diffusion of the CO. The results show that (1) the fences hinder the diffusion of the CO on the horizontal direction, but they promote the diffusion in the vertical direction. (2) The higher the fence, the more the CO concentration between the fence and the building. (3) When a ground pollutant source is on the leeward side of a building, it poses the greatest threat to the air quality around the building. It has the least threat when it is set on both sides of the building in wind direction. © Springer-Verlag Berlin Heidelberg 2014. Source

Mu K.,Harbin Institute of Technology | Liu J.,Harbin Institute of Technology | Lu Z.,Shenzhen Institute of Building Research | Zhang J.,Harbin Institute of Technology
Energy and Buildings

The actual value of the heat rejection through the cooling towers from the air-conditioning system of the typical large-scale office building is measured in the tropical summer climate of Shenzhen. The daily average measured value of the total heat rejection per unit building area is 82.75 W/m2 during weekdays. During the weekend, this value is only 20.24 W/m2, i.e., about 1/4 of that found for the weekdays, which is attributable to the less activity of building. The proportion of the sensible heat rejection is only 1.15%, and even attains a negative value when the inlet water temperature is lower than the inlet air temperature of the cooling towers. To evaluate quantitatively the effect of the heat rejection from the air-conditioning system on the urban thermal climate, the heat-rejection efficiency ratio (HRER) is presented in this study, for which the average measured value during weekdays is 1.35. In addition, a heat-rejection numerical model is developed, and the heat-rejection simulation results generally agree well with the field test data. The results indicate that the hot and humid climatic conditions impair the heat and the mass transfer efficiency of the cooling towers, and ultimately reduce the heat rejection from the building air-conditioning system. © 2015 Elsevier B.V. All rights reserved. Source

Weng X.-X.,South China University of Technology | Huang D.-J.,South China University of Technology | Li S.-F.,Shenzhen Institute of Building Research
Huanan Ligong Daxue Xuebao/Journal of South China University of Technology (Natural Science)

The pedestrian traffic system in public buildings is a nonlinear stochastic dynamic system with uncertain cluster density and interactive individuals. At present, computer dynamic simulation is one of the effective methods to investigate the dynamic characteristics of pedestrian traffic flow in public buildings. In this paper, aiming at the difference in simulation results of pedestrian evacuation obtained by several major simulation softwares in the same scene, the performance differences of the simulation software models are discussed, the simulation error due to the discrete space is analyzed, and the accuracy of the simulation models is evaluated by means of fidelity analysis. By comparing the simulated results of the travel time in the channels of the metro station with the experimental ones, it is found that the simulation performance of pedestrian traffic is closely related to the building environment, and that fidelity is important to the simulation model. Moreover, case study indicates that the multi-agent simulation model based on continuous vector space is of a fidelity up to 87% for reproducing the pedestrian behaviors in complex public buildings. Source

Gou Z.,University of Hong Kong | Lau S.S.-Y.,University of Hong Kong | Chen F.,Shenzhen Institute of Building Research
Indoor and Built Environment

A post-occupancy study was carried out to investigate the thermal environment in a high-standard office building certified by China Three-star Green Building Label. The study included a subjective evaluation of the indoor environment quality and work performance. A total of 182 office workers responded to the questionnaire survey based on the Building Use Studies (BUS) Occupant Survey and Reporting Method. Objective measurements of the thermal environment (temperature and relative humidity) under mechanically and naturally ventilated conditions were also carried out in the building. Although the thermal environment satisfied the majority of respondents, 12% and 20% reported dissatisfaction with summer and winter temperatures, respectively. The complaint on summer temperature was mainly from those working close to the chilled air outlets of the air-conditioners. The perception of cold winter temperatures revealed the potential shortcomings of sustainable building design in humid subtropical climates, where natural ventilation and passive cooling would predominate in the sustainable design while cold air in winter would tend to be neglected. The purpose of this study was to investigate the reasons why green buildings succeeded or failed to meet occupants' perception and this could have an implication in the design decisions for green building practice. © The Author(s), 2011. Source

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