Publications

With the advancement of transparent materials on building facades, solar incidence causes complex heat-flow coupling that impacts energy saving and urban heat evaluations. Environmental factors further compound such effects due to drastic optical variation caused by high-to-extreme solar angles. Yet, little is known about solar angles' impact on building facades' thermal-flow performance when applied in different climate and temporal conditions. This study proposes a new theoretical model for the naturally ventilated double-skin facade (NVDSF), focusing on addressing high to extreme solar angles' impact on passive ventilation and thermal performance. The change in latitude, season and time of the day are integrated with optical properties, energy balance and the fully-mixed model. Moreover, details of buoyancy flow are revealed numerically to deepen the understanding of radiation-convection coupling. New Incidence Angle Modifiers (IAMs) correlations, considering polarization under high angles, are empirically proposed for reflectivity, absorptivity, and transmissivity, yielding mean absolute errors of 8 %, 1 %, and 5 %, respectively. The coefficients are then integrated into a new model to reflect the angular impact on transparent panes. Compared to numerical results, the analytical model shows average errors of 4 % in natural ventilation rate, 8 % and 4 % in glazing temperatures (outer and inner). The model's implementation for a city at L = 31.15 ° during transition seasons promptly suggests the NVDSF's suitability, e.g. during the 150 days, natural ventilation provides only 33 % satisfaction for 1 m 2 NVDSF, but 95 % for 2 m 2 ; temperature differences between the outer surface and air are 39 % under 5 °C and 61 % between 5–11 °C. The new model provides a readily calculable form, supporting a new solution for future integrations with passive ventilation design, building thermal plumes and related urban evaluations.

Although solar chimney as a reliable passive renewable energy system has been widely adopted in buildings, its application in the tunnel is so far limited. By developing a validated numerical model, this study systematically investigated four critical factors that govern the effectiveness of solar chimney in tunnel applications, such as cavity height (h c ), cavity gap (L), solar radiation, and fire size. It was known that the chimney height in tunnel shows a relatively higher impact on the natural ventilation when comparing to the applications in building, but in an opposite position for the solar radiation. The natural ventilation rate is proportional to h c 0.69 in the tunnel, but the power is between 0.5 and 2/3 for building applications. The power for solar radiation in tunnel is 0.34, where it is 0.572 for building. It was obtained from an orthogonal analysis that chimney height presents a relatively higher impact on the natural ventilation performance of a solar chimney in the tunnel, but it shows an opposite phenomenon under the smoke exhaustion model. Under both natural ventilation and smoke exhaustion modes, chimney height and cavity gap show relatively stronger influence on the performance than that from the solar radiation. A theoretical model was also developed that considers both the vertically linear and horizontally parabolic temperature distributions inside the chimney cavity. The predictions when considering both distributions agree reasonably well with those numerical results, which drops about 20.6% when comparing to the predictions of those traditional models without the considerations.

Firefighting by sealing the cabin is often served as a final-taken and efficient means of suppressing ship fire. When a fire occurs in a closed engine room, it could cause the internal pressure increased and the oxygen concentration decreased, which further affects the fire burning processes. The interaction between the combustion processes and the changing environment makes sealed fires even complicated. This study investigates the behaviors of smoke plume entrainment and filling in a sealed ship engine room. Theoretical models regarding the plume entrainment and smoke filling are developed, respectively. A new reverse analysis method by coupling particle swarm optimization (PSO) with the smoke filling model is proposed to determine the unknowns in the plume entrainment model. Based on the experimental data in the literature and the reverse analysis, the explicit smoke filling model of sealed ship engine room is developed. Several previous experimental measurements and numeric simulations are used to validate its prediction ability. The results also suggest that a sealed fire has a higher smoke entrainment level than an open case. The proposed sealed ship engine room fire model can be applied to the engineering safety design of cases with potential sealed fires.

Although solar chimney as a reliable passive renewable energy system has been widely adopted in buildings, its application in the tunnel is so far limited. By developing a validated numerical model, this study systematically investigated four critical factors that govern the effectiveness of solar chimney in tunnel applications, such as cavity height (h c),cavity gap (L),solar radiation, and fire size.It was known that the chimney height in tunnel shows a relatively higher impact on the natural ventilation whencomparedto the applications in the building, but in theopposite position for the solar radiation. The natural ventilation rate is proportional to h c 0.69 in the tunnel, but the power is between 0.5 and 2/3 for building applications. The power for solar radiation in tunnel is 0.34, where it is 0.572 for thebuilding.It was obtained from an orthogonal analysis that chimney height presents a relatively higher impact on the natural ventilation performance of a solar chimney in the tunnel, but it shows an opposite phenomenon under the smoke exhaustion model. Under both natural ventilation and smoke exhaustion modes, chimney height and cavity gap show relatively stronger influence on the performance than that from solar radiation. A theoretical model was also developed that considers both the vertically linear and horizontally parabolic temperature distributions inside the chimney cavity. The predictions when considering both distributions agree reasonably well with those numerical results, which drops about 20.6% when compared to the predictions of those traditional models without the considerations.

As a practical but seldom concerned issue, the morphologic characteristics of a turbulence diffusion flame under the effects of upstream blockage in a longitudinally ventilated tunnel was studied based on a series of model-scale experiments. Different blockage sizes, blockage-fire distances, longitudinal ventilation velocities, and fire sizes were considered for research. Numerical simulations were also carried out to calculate the flow field for analyzing the causes of the variety in the flame morphology and determining the length of the near wake. Experimental results showed that the flame morphology can be divided into two stages according to the dimensionless blockage-fire distance normalized by the length of the near wake, namely flame bifurcation and flame tilt. By comparing with previous literature, the critical blockage-fire distance corresponding to the symmetrical bifurcation was achieved which follows a linear relationship with the length of the near wake. On the basic of tilt angle and centerline trajectory, dimensionless models were developed to predict the flame tilt under the effects of blocking ratio and blockage-fire distance. The research outcomes can provide a reference and tool to assess the fire risks of tunnels with blockage effects.

Latex foam based upholstered furniture has been widely used in our daily lives. Its high fire risk can be reflected by its extremely thin surface layer together with a cellular structure sponge. Therefore, through this study, an experimental study was carried out to address the fire behaviors of typical latex foams, including cotton, hemp, silk, and blending coated latex foam. The thermal properties and structure of these fabric materials and latex foam were analyzed experimentally, together with the analysis of the heat transfer mechanism and the calculation of flame spread rate. Experimental results showed that the thin surface fabric covered on the surface of the latex foam could prolong the combustion process for more than 150 s. The peak bottom flame area of the silk coated sample was only 40 % of the uncoated one. The combustion residues of the surface fabric after the extinguishment were found composing of carbonized fabric and white ash. It was then known that the cotton fabric shows significant effects on the combustion processes due to dense residues. The average flame spread rate of the coated samples was about 22 % of those uncoated ones. The porosity of the fabric residues on the surface played a key role in the flame spread on the latex foam surface. A flame spread rate model was developed and validated for the first time that considered the fabric porosity, which could provide a useful tool for the relevant fire risk evaluation for those practical fire scenarios with multi-layer combustible.

Liquid pool fires in a well-confined ship cabin are experimentally studied. The experimental results showed that the fuel consumption ratio remains stable in the oxygen-lean mode in the well-confined environment for both the tested fuels (i.e., n-heptane and diesel) in this study. The n-heptane pool fire exhibited five burning stages (i.e., initial growth, stabilized burning, transition, boiling, and decaying), while the diesel only showed three stages (i.e., initial growth, stabilized burning, and decaying). Boiling combustion behaviors were not observed when the pool diameter is bigger than 30 cm, but an unusual phenomenon of ghost fire appeared in the later burning stage. Under the oxygen-lean mode, the fuel consumption ratio of n-heptane is 0.19–0.26; and it is about 0.28 for diesel. In the well-confined space, the average mass loss rate per unit area did not change too much under various pool sizes. The average mass loss rate of the n-heptane was observed greater than that of diesel. Besides this, a theoretical model was developed to predict the mass loss rate of liquid fires in a well-confined space, where the predictions agree reasonably well with the experimental data, showing an average discrepancy of less than 10%.

Silica aerogel shows great potential in the relevant high-temperature applications, such as furnaces, tubes, and bricks. The related studies on addressing its behaviors under high temperatures are critically needed. Through this study, the effects of heating rate on its high-temperature behaviors of silica aerogel granule with a size of 100 mesh were addressed experimentally, including density, pore size distribution (PSD) and so on. It was known from the experimental results that the skeleton density increases under a relatively higher heating rate, while the densification, shrinkage, and fractional density show a decreasing trend. The mean coordination number of tested silica aerogel was obtained within a range of 2.016–2.034 contacts. The confusing of the primary particle was found mainly occurring at the sample surface for all the tested samples. It was also known that the diameter of the primary particle increases from 44 to 71 nm when the heating rate increases from 5 to 20 °C/min, but for the particle, it shows a decreasing trend. After the heating processes, the pore model of the sample was changed from cylinder to slit-shaped. A fast heating rate was found to promote the transfer from the Si–OH group to the Si–O–Si group.

Although solar photovoltaic (PV) panels are widely used in buildings, previous studies mainly focused on optimizing energy performance and studies on their fire characteristics were limited, substantially affecting PV panel design and practical use. Therefore, the fire characteristics and applicability of three types of solar PV panels were assessed by combining experimental data and experts’ assessments. Under fire conditions, the temperature rising rate of the unexposed surface of the non-hollow transparent panel is 1058.3% and 47.2% greater than those of the hollow transparent and non-hollow opaque samples, respectively. The opaque sample's cracking start time and temperature are 186 s and 266.4 °C, respectively, around 44.5% and 41.8% of those of the transparent sample. The opaque sample showed the longest crack of 115.31 m, whereas the non-hollow transparent sample had the largest proportion of glass falling-off area of 8.76%. The fire risks of various PV panels differ under different scenarios. Experimental results and experts’ assessment indicated that hollow transparent PV panels with low fire risk could be used in buildings with high population density, while non-hollow opaque PV panels could be used in scenarios like PV power plants with less population; and the non-hollow transparent PV panels have a considerable fire risk, yet they can be employed in places with low safety requirements or no fire concerns. The obtained research outcomes can guide the selection of solar PV under various practical scenarios.