Publications

Curved flame is one of the determining aspects in evaluating the risk of tunnel fire. In this study, a series of experiments are carried out to investigate the characteristics of fires in a reduced-scale tunnel model, including the center-line trajectory, length and tilt angle of curved flame. It can be known from the experiments that the total flame length in the tunnel without longitudinal ventilation is almost equal to that in open space. For the flame in the tunnel with longitudinal ventilation, a third-power relationship is shown in the center-line trajectory equation of the curved flame. Meanwhile the length of curved flame can be obtained by the method of calculus. Based on the experimental data from this study, an empirical model is developed to predict the tilt angle of the curved flame, which is based on Oka’s model but with much improved accuracy for the curved flames in the tunnel.

No abstract is provided for this article.

Disposal of plastic waste poses a significant scientific challenge due to its non-biodegradable properties, increasing volume of production, and low recycling rate. One potential solution is its’ manufacture into void formers for use in concrete building elements. However, plastics soften and decompose when exposed to high temperature fire which poses a challenge for fire safety design and certification of construction elements. A combined experimental and numerical study is presented to determine the fire resistance of concrete building elements that incorporate a novel recycled plastic void former (ROBOVOID, US patent No. 11,352,789). Multiple experimental fire exposure tests are performed to determine fire resistance and assess thermally induced damage for various building elements incorporating ROBOVOID. The fire resistance of the voided elements increased as the concrete content increased, or the fire intensity or exposure duration decreased. A finite element model is presented that can predict the thermal response of the building elements when subject fire representative of the Australian Standard Bushfire Attack Level (AS 1530.8.1), Building-to-Building (AS 5113) and Fire Resistance Level (AS 1530.4) conditions. The analysis indicates that polymer-based void formers can be incorporated into concrete structures while maintaining a high level of fire resistance for a variety of fire conditions.

The societal risk acceptance criteria (SRAC) are used in the shipping industry as a ruler to judge whether the actual ship risk is in control. To exploringly refresh SRAC for general cargo ship formulated by International Maritime Organization (IMO) in 2000, a comprehensive analysis was performed by using the accident data recorded in the Marine Casualties and Incidents (MCI) module of the Global Integrated Shipping Information System (GISIS) database from 2005 to 2019. The risk levels of four typical accident factors, including initial event, ship size, classification society, and geographical zone, were evaluated. The results illustrate that the SRAC established in this study for general cargo ship fatality accidents are found stricter than that by IMO presented in 2000. Fire/explosion and capsizing show the highest societal risk levels in the initial events, and large general cargo ships face higher societal risk. In addition, ships that do not belong to the International Association of Classification Societies (IACS) are at a higher risk than IACS ships. And the societal risk levels of fatality accidents in East & Southeast Asia and injury accidents in Europe, the Mediterranean & Black Sea are higher than those in the other zones.

Thermochromic (TC) glazing is an advanced smart window technology that can help to achieve nearly zero-energy buildings. The glazing temperature that affects TC thermo-optical properties directly impacts its energy-saving performance. However, the impacts of solar radiation and natural convection occurring on this temperature-sensitive material are not yet fully understood. Compared to previous focuses on material properties and energy evaluation, this study aimed to provide a different view from thermo-fluid dynamics on the heat transfer characteristics of a TC window, with impacts of environmental factors addressed. A validated Computational Fluid Dynamics (CFD) model identifies the environmental impacts on the TC glazing temperatures under the coupled radiative and convective heat transfer. Furthermore, a theoretical model was developed with an empirical factor obtained from CFD results. It enables a simple calculation to obtain the TC glazing’s temperature by using solar factors, outdoor temperatures and optical properties. The model suggests that the temperature difference between the TC glazing and the ambient is a function of absorbed solar irradiation ( ∝ q ̇ total 0.75 ). The predictive model is then tested using typical climate conditions in three cities in China with different solar angles, which demonstrates good agreement with an average absolute error of 5% compared to simulated glazing temperature. This estimation method can further assist in material design, product selection and Building Energy Simulations to achieve a TC window design that is ‘smart’ on seasonal change requirements for different regions.

No abstract is provided for this article.

To date, the development of safe and robust lithium-ion batteries is still hindered by the commercial polyolefin membrane due to its poor thermal stability and inferior electrolyte wettability. Thus, to address this shortcoming, an advanced polyimide aerogel separator was designed by simple one-pot reaction via co-precursor and cross-linking methods in this work. Based on molecular structure designation and gelation time control, the as-prepared polyimide aerogel separator (C-PI separator) possessed high porosity, good flexibility, excellent thermal stability, and superior electrolyte wettability, which are essential attributes of a high-performing separator. LiFePO 4 |Li metal battery was later assembled with C-PI separator, and the cell demonstrated outstanding long-term cyclic performance (>1000 cycles at 1C with 93.6% retention). Compared with PE separators, the NCM523- graphite pouch cell assembled with C-PI separators exhibited high thermal stability with a higher thermal runaway temperature (204.9 ºC vs. 140.4 ºC) and a lower maximum temperature rise (0.06 ºC /min vs. 8 ºC/min), demonstrating its application potential in scenarios with high requirements for safety. Furtherly, the thermal runaway mechanisms of the full cells were explored and explained in this work.

In order to improve their thermal insulation performance, silica aerogel reinforced polytetrafluoroethylene (PTFE) composites with 10–30 wt% silica aerogel were prepared and tested. The morphology, density, structure and thermal properties of the composites were characterized through scanning electron microscopy, infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller analysis, thermo-gravimetric analysis (TGA) and thermal conductivity analysis. A theoretical model of the effective thermal conductivity (ETC) was developed based on the three-level homogenisation theory. It was found that the density of the composites decreases linearly with the mass fractions of silica aerogel. The composites showed remarkable smaller pore radius (1–10 nm) when compared to that of the pure silica aerogel (10–35 nm). The FTIR and TG results confirmed that the reaction of silica aerogel and PTFE occurs during the mixture or heating stage. But the reaction did not effect the structure of the composites. Moreover, the ETC of the composites along the silica aerogel contents can be divided into two stages, where the critical content is 18 wt%. The lowest thermal conductivity can reach 0.13 W m−1·K−1. The ETC of the composites predicted by the theoretical model is in good agreement with those experiment results. The volume fractions of the PTFE in the silica aerogel pore are 87% and 73% for the two stages, respectively, and mainly the large pores on the surface of the silica aerogel particles are filled by PTFE.

Solar chimney is a reliable renewable energy system that enhances the natural ventilation to reduce the energy consumption in buildings. Under the fact that previous optimization designs usually ignore the external wind, the impacts of external wind on the optimum designing parameters are then investigated. It is confirmed that external wind could affect its optimum designing parameters, which are different from those previously obtained value in the literature without considering the external wind. For the analysed wall solar chimney, it was known that previously obtained optimal cavity depth of 0.2–0.3 m is no longer applicable under the external wind, and the optimal value rises to 0.4–0.5 m, while the same applies to inlet height/area. Solar chimney performance is enhanced under the external wind, which is not only because of the incoming wind flow from the room opening but also the reduced air resistance. It was observed that increased solar intensity shows limited influences on the overall airflow characteristics. Solar chimney performance also presented a generally enhanced trend under a low external wind speed, but a strong wind could dominate its performance with limited fluctuation even though the wind angle is higher as 45°. It was known that the airflow rates through the solar chimney are largely hampered with a small cavity depth (i.e., smaller than 0.2 m) and inlet height under the external wind. And the airflow profiles are less affected when both of cavity depth and inlet height are bigger than 0.2 m. The obtained research outcomes could provide a technical guide on the optimization design of solar chimney in buildings.

Double skin façade (DSF) as a passive renewable technique has been widely used due to its ability to reduce energy consumption by enhancing natural ventilation. However, previous studies mainly focused on its optimization designs, and its potential risks as determining factors have been less explored. This study reviewed three typical potential risks of DSF, including overheating, structural, and fire risks, and analyzed their manifestations, influencing factors, and possible mitigation. The overheating risk, mainly from direct sunlight and inadequate ventilation, can be mitigated by optimizing DSF design parameters or adding additional components. Wind-induced vibration, earthquake, or blast impact are the causes of the second risk, structural damage to DSFs. Appropriate building shapes and vent sizes can improve airflow inside and outside the DSF and reduce wind-induced vibrations. Regarding strong shocks, dampers can be used to eliminate excessive movement. Heat and smoke from a fire show complex coupling effects on the structures of DSFs, propagating along the cavity and causing flame spread, glass cracking, and else. Optimizing DSF design parameters and adding perforated plates and refractory glass can reduce the risk of fire to DSF. It is crucial to consider the relevance of the thermal performance of various DSFs to safety. Different types of DSFs have different potential risks, so it is necessary to fully consider not only their energy performance but also their application scenarios and the corresponding areas where risks will occur. This study provides a guideline for designing and optimizing DSFs regarding risk mitigations.

Solar chimneys under heating modes are much more complicated than those under cooling modes, as their performance should consider both airflow rate and temperature rise. Their heating performance and optimization designs are still unclear under various heating modes. This study then addressed the impacts of typical design factors on their heating performance numerically and empirically under three heating modes, including two fresh-air heating modes (i.e., through inlet and window) and a sealed heating mode. Similar to the cooling mode, the impacts of the analyzed design factors on the temperature rise and airflow rate can be expressed by the exponential function. Differently, the cavity gap under the three heating modes shows negative exponentials (−0.18 to −0.088), while the cooling model is between 0.652 and 0.756. Solar radiation shows positive exponential under both heating and cooling modes, and its impacts on airflow rate are relatively higher under cooling mode. Also, the temperature rises within both the chimney cavity and the attached room along the height show natural exponential functions. A lower window (or even closing it and replacing it with a bottom vent near the floor for fresh air supply) is suggested for the two heating modes with fresh air supply to avoid vertical temperature differences inside the room. Compared to the fresh air through inlet, sealed heating offers a 292.8% higher air temperature rise and 3.9% lower airflow rate, whereas fresh air through window offers a 19.3% higher airflow rate and 44.5% higher air temperature rise. Therefore the modes of fresh air through inlet and window can be applied to those locations under cool and cold climates, respectively; sealed heating is only applicable to those scenarios without or with limited occupants (i.e., storage) as no fresh air is supplied.

Fire behavior of natural rubber latex foam under different thickness conditions(d=1,2and 5cm)were explored though a little of experiments by using the self-built small scale experimental platform. It can be shown that the flame spread law of thermally thin and thermally thickness are different. Natural rubber latex foam with thickness of 2cm show higher fire risk, which value of flame spread rate, maximum flame height, maximum mass loss rate and maximum temperature is 0.00293m/s, 851.875mm, 1.83g/s, 948K,repectively.That may because the thickness of residue formed of thermally thick materials is larger than the thin one, obstructing the contact of the natural rubber latex foam with fresh air .In addition, a special phenomenon is noticed that during the second stage, the bottom unburned zone located in the four edges(thermally thin material) and middle player(thermally thick material).

Naturally ventilated double skin façade (NVDSF) utilizes solar radiation to introduce natural ventilation through a double-skin façade cavity with vents. It is an easy-to-implement green technology that can be widely applied to new or existing buildings. However, its implementation in buildings is still limited as the coupled radiation and natural convection pose challenges in predicting ventilation performance. Moreover, the diversity of real-life applications raises a great need for a universally applicable method that can account for realistic design factors. Hence, an in-depth theoretical analysis model is required to facilitate the application of NVDSFs in buildings. This study proposes two new analytical models for NVDSFs that can directly predict ventilation rates with simple inputs. Numerical simulations are also conducted to validate the developed analytical models. It demonstrated that the experimentally validated numerical model can offer accurate predictions of natural convection and radiation for the case that involved complicated environmental, structural, and material factors. Most importantly, the realistic scenarios, NVDSFs with exterior vent louvers are studied both analytically and numerically. Different optical properties from two glazing materials, regular glass and low-e glass, are also tested with the proposed analytical models. Through validation, the discrepancies of the predictions by the proposed analytical models are −5% to −9% for ‘no-louver’ NVDSF for two different glazing materials (i.e., regular and low-e glass), and 13%–27% for NVDSFs with adjustable louver angles 45°–150°.