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Wang Z.,Shenzhen Institute of Building Research | Wang Z.,Laboratory of Building Energy Efficiency and Applied Technology in Guangdong Province | Pei J.,Tianjin University | Zhang J.S.,Syracuse University
Building and Environment | Year: 2012

A numerical model for simulating the performance of a dynamic botanical filtration system has been developed for the first time. The model accounts for the various transport and storage processes including air and contaminant convection, adsorption of non-water soluble compound by activated carbon, absorption of water soluble compound by water, bio-degradation of chemicals by microbes in the root bed as well as the automatically controlled irrigation system for the root bed. The model was built upon an existing Coupled Heat, Air, Moisture and Pollutant Simulation for Building Envelope System (CHAMPS-BES) model with the addition of bio-degradation process and the irrigation system. Model parameters were estimated from the experiments. The simulation results showed that the model could describe the pressure drop and airflow relationship well by using the air permeability as a model parameter. The water source added in the model also led to the similar bed moisture content and outlet air RH as that in real test case. The simulation results also showed that the developed model worked well in analyzing the effect of different parameters. It was also found that the critical bio-degradation rate constant was 1×10 -5s -1 in this study, below which the dynamic botanical filtration system would not be able to sustain the formaldehyde removal performance. The bio-degradation rate constant of the reduced scale filter system tested was estimated to be in the range of 0.8-1.5×10 -4s -1. © 2012 Elsevier Ltd.

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 | Year: 2016

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.

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) | Year: 2012

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.

Shen H.,Xi'an Jiaotong University | He Q.,Shenzhen Institute of Building Research | Huang Y.,Xi'an Jiaotong University | Liu Y.,Xi'an Jiaotong University
Lecture Notes in Electrical Engineering | Year: 2014

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.

Huang Y.,Xi'an Jiaotong University | He Q.,Shenzhen Institute of Building Research | Shen H.,Xi'an Jiaotong University | Liu Y.,Xi'an Jiaotong University
Lecture Notes in Electrical Engineering | Year: 2014

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.

Gao N.,Tongji University | He Q.,Shenzhen Institute of Building Research | Niu J.,Hong Kong Polytechnic University
Building Simulation | Year: 2012

This paper adopts an Eulerian-Lagrangian approach to investigate the lock-up phenomenon (or trap phenomenon) of human exhaled droplets in a typical office room under displacement ventilation (DV). A particle-source-in-cell (PSI-C) scheme is used to correlate the concentration with the Lagrangian particle trajectories in computational cells. Respiratory droplets with sizes of 0. 8 μm, 5 μm and 16 μm are released from a numerical thermal manikin (NTM). The influence factors including indoor temperature gradient, heat source configuration and exhalation modes are studied. It is found that large temperature gradient would result in trap phenomenon of small exhaled droplets (smaller than 5 μm). The intensive heat source near the NTM could help to transport the small droplets to the upper zone and decrease the concentration level in the trapped zone. Both nose-exhaled and mouth-exhaled small droplets would be trapped at the breathing height when temperature gradient is sufficiently high. However, the trap height of the droplets from mouth is a little bit higher. Because of large gravitational force, it is difficult for the thermal plume to carry 16 μm respiratory droplets to the upper zone. © 2012 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

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 | Year: 2012

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.

Wang X.,Harbin Institute of Technology | Wang X.,Shenzhen Institute of Building Research | Zha X.,Harbin Institute of Technology | Zhu Y.,Harbin Institute of Technology
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2014

The fire performance of concrete beams reinforced with GFRP rebar was studied in this paper by the method of numerical simulation and theoretical calculation. Finite element models of concrete beam heated by ISO 834 standard heating curve were developed, and the suitable thermal and thermodynamic parameters were selected for the analysis. The accuracy of FEA model was proved by the comparison with the results of fire experiments, and different influencing factors were taken into account for the parametric studies to describe the fire performance. FEA results indicate that the fire behavior of GFRP reinforced concrete beams is only controlled by three factors: loading rate, GFRP rebar position, and the time exposed in fire. Refer to the structure fire design of steel reinforceal concrete in Eurocode 2, the inhomogeneous material properties under fire exposure can be assumed as homogeneous by reduced cross-section of concrete. The load-bearing capacity of the GFRP reinforced concrete members in fire environment can be calculated by the reduction of concrete cross section exposed in fire and the equivalent strength of GFRP rebars in different positions with different temperatures. The theoretical design method proposed in this paper shows good agreement with FEA results, which can be used to calculate the bearing capacity of GFRP reinforced concrete beams in fire environment.

Li N.,Hunan University | Ma J.,Hunan University | Liu G.,Shenzhen Institute of Building Research | Li X.,Hunan University
Taiyangneng Xuebao/Acta Energiae Solaris Sinica | Year: 2013

Two groups of flat plate solar collectors which were respectively in simulative dusty and clean condition were researched in the same conditions of circumstances, and the effects of various mass of dust on their thermal properties was researched by comparing their instantaneous efficiencies and efficiency curves. The results of experiment showed that the dust not only reduced the instantaneous efficiency of the collector, but also lowered the highest efficiency and temperature which it can reached; The value of efficiency declining is in direct proportion to the mass of dust, Δηd=0.089lnm-0.118; The surface of collector should be kept cleaning in the arid area or season, especially in the early days of dust accumulation; If we intend to obtain higher thermal properties in operating course for collector, we should not only improve its performance, but also attach importance to its operational maintenance.

Shen H.,Xi'an Jiaotong University | He Q.,Shenzhen Institute of Building Research | Liu Y.,Xi'an Jiaotong University | Zhang Y.,Xi'an Jiaotong University | Dong B.,Xi'an Jiaotong University
Building Simulation | Year: 2014

The airflow around a building is in high Reynolds number flow regime. It can be calculated by large eddy simulation method (LES). The air temperature around buildings is passive scalar. If the behavior of passive scalars is considered with sub-grid scale (SGS) model for LES, the calculation or the results will be improved greatly but it has not been implemented, till now. In this paper a passive scalar SGS model (PS-SGS) was derived based on the hypotheses about the sheet-like structure in Taylor scale. The kinetic-energy SGS model was improved with the derived PS-SGS. The validity of the model was checked out using the experimental data in reference. The field around a supposed two-dimensional building was estimated with the improved kinetic-energy SGS model. Karman vortex-street and some special behavior for passive scalars were distinguished with the derived model. © 2014 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

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