Collaborative Innovation Center for Urban Public Safety

Hefei, China

Collaborative Innovation Center for Urban Public Safety

Hefei, China
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Cong H.Y.,Hefei University of Technology | Wang X.S.,Hefei University of Technology | Wang X.S.,Collaborative Innovation Center for Urban Public Safety | Zhu P.,Hefei University of Technology | And 2 more authors.
Applied Thermal Engineering | Year: 2017

This study investigated the smoke extraction process by natural ventilation through a vertical shaft. In addition, the factors restricting smoke exhaust, such as plug-holing and boundary layer separation are discussed. Accordingly, a new concept (board-coupled shaft) is introduced to solve the dilemma. By installing a thin board under the shaft, the negative effect of plug-holing can be eliminated, leading to higher smoke-extraction efficiency in the shaft. Numerical simulations were performed using the Fire Dynamic Simulation (Version 6.1.2). The influences of board location and fire heat release rate on smoke extraction were investigated. Furthermore, the validity of this model was proved, and the results indicate that the distance between the board and shaft should be properly selected. In addition, a new empirical model was deduced to predict the mass flow rate inside the shaft, which agrees well with the experimental data. © 2017 Elsevier Ltd


Wang Y.,National University of Singapore | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | Wen J.X.,University of Warwick | And 2 more authors.
Applied Thermal Engineering | Year: 2017

To make constructions more artistic, various new kinds of glazing are increasingly employed in building envelopes. However, when subjected to a fire, these glass façades may easily break and fall out, significantly accelerating the development of enclosure fire. Thus, it is necessary to investigate and compare their different fire performance and breakage mechanisms. In this work, a total of ten tests, including single coated, insulated and laminated glazing, were heated by a 500 × 500 mm2 pool fire. Breakage time, glass surface and air temperature, incident heat flux and crack initiation and propagation were obtained. The critical conditions of three different kinds of glazing were determined. It was established that the insulated and laminated glass can survive longer than the single glass. The air gap and fire side glass pane was found to play a key role for the thermal resistance of ambient side pane in the insulated glazing. Although both panes of the laminated glazing broke, it could be held together by the layer of gel, effectively avoiding the formation of a new vent. Numerical simulations were performed to investigate the heat transfer process through the glazing panels and the temperatures in the glazing were predicted well. Suggestions for glass fire resistance design are proposed. © 2017 Elsevier Ltd


Wang Y.,National University of Singapore | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | Su Y.,Hefei University of Technology | And 3 more authors.
Fire Safety Journal | Year: 2017

Double glazing is increasingly employed in glass curtain walls, but very little is known about its thermal response under fire conditions. In this work, a total of twenty seven 600 × 600 mm2 double glazing units, with 6 mm, 9 mm and 12 mm air spacings, were tested. Three different installation types were adopted: 1) exposed frames, 2) horizontal-hidden frames and 3) vertical-hidden glass in order to study their potential effects on the glazing breakage behavior. A 500 × 500 mm2 n-heptane pool fire was used to heat the glass panes. The breaking time, surface temperature, total heat flux, heat release rate, and crack and fallout morphology were measured and analyzed. The test result suggests that different installation types have a significant effect on the fracture behavior of double glazing, especially for glass panes located at the fire side. Glass in exposed framing is more prone to cracks than those in semi-exposed frame, but fallout may more easily occur in semi framing façades. When no, or very limited fallout occurs at the fire side pane, thicker air space leads to a longer breakage time of ambient glass panes, thus improving the unit's integrity during fire. The experimental results obtained in this study is valuable for the development of practical guidelines for fire safety design. © 2017 Elsevier Ltd


Gong J.,Hefei University of Technology | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | Sun J.,Hefei University of Technology
Thermochimica Acta | Year: 2017

Thermogenesis mechanism in the aspect of structural level and thermal hazard to the lithium ion battery are systematically analyzed for Li(NixCoyMnz)O2(NCM, x = 1/3, 0.5, 0.6, 0.8). All the results confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, alternating current impedance and a C80 micro-calorimeter indicate that with the increase of nickel content, the structure of NCM materials tends to collapse causing heat and the valance of Ni element is high enough to oxidize the electrolyte accelerating the decomposition of the electrolyte, also some electrolyte decomposition products are speculated to cover on the surface of the cathode with larger inner resistance for the battery. The thermal tests display that the total exothermic heat of both NCM-electrolyte system and full-cell system increases with increasing nickel content, which testifies the risk of high-nickel NCM to the lithium ion battery. © 2017 Elsevier B.V.


Luo L.,Hefei University of Technology | Yang L.,Hefei University of Technology | Yang L.,Collaborative Innovation Center for Urban Public Safety | Fu Z.,Southwest Jiaotong University | Fu Z.,University of South China
Advances in Intelligent Systems and Computing | Year: 2018

It may encounter some severe problems when simulating a crowd evacuation using human’s data collected from other countries. Thus, to ensure the safety of people in buildings, it becomes quite important to gather and analyze human’s behavior and reaction in fire, with consideration of different culture backgrounds, behavior habits, different physiology and psychology characteristics et al. In this study, we designed questionnaires and analyzed human’s individual characters, cognition degree of fire, sociological behaviors, as well as daily behavior characteristics statistically in multi-ethnics jumping-off of China. We bridged the gap between the human’s characteristics (such as gender, age, education, job, environment cognition and toxic tolerance) and human’s behavior in fire. © Springer International Publishing AG 2018.


Zhang T.,Hefei University of Technology | Zhou X.,Hefei University of Technology | Yang L.,Hefei University of Technology | Yang L.,Collaborative Innovation Center for Urban Public Safety
Materials | Year: 2016

This work investigated experimentally and theoretically the fire hazards of thermal-insulation materials used in diesel locomotives under different radiation heat fluxes. Based on the experimental results, the critical heat flux for ignition was determined to be 6.15 kW/m2 and 16.39 kW/m2 for pure polyurethane and aluminum-polyurethane respectively. A theoretical model was established for both to predict the fire behaviors under different circumstances. The fire behavior of the materials was evaluated based on the flashover and the total heat release rate (HRR). The fire hazards levels were classified based on different experimental results. It was found that the fire resistance performance of aluminum-polyurethane is much better than that of pure-polyurethane under various external heat fluxes. The concentration of toxic pyrolysis volatiles generated from aluminum-polyurethane materials is much higher than that of pure polyurethane materials, especially when the heat flux is below 50 kW/m2. The hazard index HI during peak width time was proposed based on the comprehensive impact of time and concentrations. The predicted HI in this model coincides with the existed N-gas and FED models which are generally used to evaluate the fire gas hazard in previous researches. The integrated model named HNF was proposed as well to estimate the fire hazards of materials by interpolation and weighted average calculation. © 2016 by the authors.


Yan J.,Hefei University of Technology | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | Wang Q.,CAS Hefei Key Laboratory of Materials for Energy Conversion | And 3 more authors.
Applied Thermal Engineering | Year: 2016

One kind of composite board based battery thermal management system (BTMS) is proposed and a three-dimension battery thermal model is proposed in this work. The composite board consists of three parts with a sandwich structure, which contains a heat conducting shell, an insulation panel and phase change material (PCM). Then four different modes are compared in detail to verify the thermal performance of the composite board under normal operating condition and thermal abuse condition. The results show that the composite board can effectively improve the heat dissipation capability and the uniformity of the temperature, meanwhile it can enhance the heat-insulation capability of the battery pack to prevent the thermal runaway propagation. In addition, increasing the latent heat of PCM can greatly improve the thermal performance of the composite board, thus the PCM with a latent heat of 1125 kJ/kg and the phase change temperature between 303.15 K and 323.15 K are recommend to be used in the battery thermal management. © 2016 Elsevier Ltd


Ping P.,Hefei University of Technology | Ping P.,China University of Petroleum - East China | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | And 5 more authors.
Journal of Power Sources | Year: 2015

Abstract A full-scale burning test is conducted to evaluate the safety of large-size and high-energy 50 Ah lithium-iron phosphate/graphite battery pack, which is composed of five 10 Ah single cells. The complex fire hazards associated with the combustion process of the battery are presented. The battery combustion behavior can be summarized into the following stages: battery expansion, jet flame, stable combustion, a second cycle of a jet flame followed by stable combustion, a third cycle of a jet flame followed by stable combustion, abatement and extinguishment. The multiple jets of flame indicate serious consequences for the battery and pose a challenge for battery safety. The battery ignites when the battery temperature reaches approximately 175-180 C. This critical temperature is related to an internal short circuit of the battery, which results from the melting of the separator. The maximum temperature of the flame can reach 1500 C. The heat release rate (HRR) varies based on the oxygen generated by the battery and the Joule effect of the internal short circuit. The HRR and heat of combustion can reach 49.4 kW and 18,195.1 kJ, respectively. The state of charge of the battery has a significant effect on the maximum HRR, the overall heat generation and the mass loss of the battery. © Elsevier Inc. All Rights reserved.


Sun Q.,Hefei University of Technology | Wang Q.,Hefei University of Technology | Wang Q.,Collaborative Innovation Center for Urban Public Safety | Wang Q.,CAS Hefei Key Laboratory of Materials for Energy Conversion | And 3 more authors.
Energy Conversion and Management | Year: 2015

To analyze the thermal behavior of 945 mA h lithium titanate battery during charging and discharging processes, the experimental and numerical studies are performed in this work. The cathode and anode of the 945 mA h lithium titanate soft package battery are the lithium nickel-cobalt-manganese-oxide and lithium titanate, respectively. In the experiment, an Accelerating Rate Calorimeter combined with battery cycler is employed to investigate the electrochemical-thermal behavior during charge-discharge cycling under the adiabatic condition. In numerical simulation, one electrochemical-thermal model is adopted to predict the thermal response and validated with the experimental results. From both experimental and simulated results, the profile of potential and current, the heat generation, the temperature, the temperature changing rate and the temperature distribution in the cell are obtained and thermal runaway is predicted. The analysis of the electrochemical and thermal behavior is beneficial for the commercial application of lithium titanate battery in the fields of electric vehicles and hybrid electric vehicles. © 2014 Elsevier Ltd. All rights reserved.


He S.,Anhui University of Science and Technology | Li Z.,Anhui University of Science and Technology | Shi X.,Anhui University of Science and Technology | Yang H.,Anhui University of Science and Technology | And 3 more authors.
Advanced Powder Technology | Year: 2015

In this study, we tried to synthesize ultralow density and super hydrophobic silica aerogel with extra high specific surface area, by using absolutely cost effective processing from sodium silicate. Hydrosol was obtained through ion exchange. To reduce the processing time, the gels were mechanically agitated to granules before solvent exchange. N,N-Dimethylformamide (DMF), serving as drying control chemical additive (DCCA), was introduced to reduce shrinkage. When the molar ratio of Si in sodium silicate to DMF is 0.31, the pore size distribution is the narrowest. Before dried under ambient pressure, the gels were surface modified by Trimethylchlorosilane (TMCS) in order to make sure the aerogels are hydrophobic. And the proper molar ratio of TMCS to pore water is 0.0233 which is much lower than that in previous experiments. The resulting aerogels have well-developed mesoporous structure with extremely high specific surface area (817 m2/g) and super hydrophobicity (contact angle of 165°). © 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

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