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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.

Silica aerogel is a unique three-dimensional nano-porous material and its characteristics have attracted much attention from both engineers and researchers. However, their structural behaviors under high temperature are not well known yet. The structure of silica aerogel under high temperature from 950°C to 1200°C was investigated based on pycnometry, scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction patterns (XRD). It was obtained that the structure of silica aerogels was strongly affected by heating temperature and time. It was known based on experimental results that the changes of silica aerogel during 950–1200°C can be divided into three steps: expansion of primary particles at sample surface (step I), atrophy and pore collapse of primary particles at the surface (step II), and atrophy and pore collapse of primary particles inside the sample (step III). Change rate was found significantly dependent on the moving rate of expansion region, while during the first two steps only limited changes were observed about three dimensional nanoporous structures. During Step III, the structure of silica aerogel was completely destructed, while the density can reach to about 1600kg/m3.

Solar chimneys as cost-effective renewable energy systems offer significant energy saving in buildings through the enhanced natural ventilation. Previous studies have focused on the fluid dynamics of the solar chimney itself. Still, few studies were found in the literature on its assessment on the energy performance in buildings, such as addressing how many percentages of energy can be saved based on it in buildings. This is mainly due to the relevant challenges of the assessment methods, such as absent functions, modeling accuracy, experimental validation, and the capability of addressing many influencing factors. To overcome the constraints, five typical energy assessment methods were critically reviewed through this review, including hydrostatic pressure, thermal network, zonal model, theoretical/empirical models, and computational fluid dynamics (CFD) modeling. This is the first review paper specified for the energy assessment methods of solar chimneys. The major influencing factors of solar chimney include configuration, installation conditions, material usage, and environment. The current energy assessments for solar chimneys are primarily based on the thermal network and zonal model (or the combination) but not CFD modeling. The current challenge for hydrostatic pressure analysis is its applications in multiple chambers, especially with those large openings (e.g., doors and windows). The thermal network could overcome this challenge, but its modeling accuracy and generality still require effort. Due to many influencing factors, a single assessment method may not be viable for practical implementation. Future research on energy assessment could be in several directions, such as a combined zonal and CFD modeling, the validity and uncertainty of those energy assessments in practical building applications, and detailed and comprehensive experimental tests for the validation.

Although a combination of various (or types of) solar chimneys (SCs) can overcome the limitations of a solo system, the interactions, designing factors and overall performance in one building are still not known. Therefore, a combined wall and roof SCs were investigated both numerically and theoretically through this study. After being coupled with a roof SC, the performance of the wall SC is generally enhanced, which is quite stable when the designs of the roof solar chimney keep changing. The optimal designs of the wall SC are basically the same with those without coupling a roof SC. Furthermore, the window area shows an obvious impact on the roof SC but not the wall SC. Solar radiation offers an obviously positive effect on both the wall SC and the overall performance, while its impacts on the roof SC are relatively less obvious. The optimized design of the combined system can be achieved with specific designs, such as possibly big absorption walls for both chimneys, a big window, an appropriate level of cavity gap and air inlet height for the wall SC, a relatively small cavity gap for the roof SC, and a closer wall and roof SCs. A theoretical model is also developed to predict the airflow rates through both the wall and roof SCs. A coefficient, namely α, is proposed to describe the percentage of the airflow from the window to the wall SC. The predictions based on fixed α obey well with those numerical results.

High-performance silicon carbide (SiC) aerogels with excellent high-temperature resistance and high porosity are highly desirable in the fields of thermal insulation and adsorption. However, constructing a super-elastic SiC aerogel and controlling its properties is still a significant challenge. To better regulate its properties, it is necessary to clarify its reaction and growth mechanism. Here, we propose an in-situ reactive growth strategy to prepare super-elastic SiC aerogels. The obtained aerogels can withstand 80 % deformation and exhibit an ultra-low thermal conductivity of 0.024 W·m−1 K−1. Furthermore, the aerogel shows a superior electromagnetic wave (EMW) absorption performance with a minimum refection loss (RLmin) value of – 40.7 dB. More importantly, we reveal the mechanism of the reaction and growth of SiC crystal. The growth process of SiC crystal can be divided into three stages: pyrolysis, nucleation and growth. Based on understanding the growth mechanism, we can further regulate the structures of SiC crystals by controlling the sintering time, including sea urchin-like, nanorod-like, nanowire-like and slub-like shapes. This study provides a new idea for preparing super-elastic SiC aerogel and regulating its structure.

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.

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.