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As buildings are always in a windy environment, in many cases the influence of the environmental wind cannot be neglected. Therefore, this work conducted an experimental study of the influence of environmental wind on the smoke flow behaviour and temperature distribution in the typical room-corridor fire. In the experiments, different wind velocity and HRR (heat release rate) were tested. Experimental results indicated that the environmental wind would exhibit an obvious influence on the spilled smoke flow in the corridor. When the wind velocity is relatively small, the environmental wind has a positive effect on the spilled smoke flow, and the smoke distribution would show a symmetrical and high temperature region, which would become larger with the wind velocity. With the continuous increase in the velocity, the smoke would be blown downstream of the corridor, causing an obvious decrease in the maximum ceiling temperature. To characterize the temperature distribution along the corridor ceiling, a one-phase exponential correlation is proposed to predict the ceiling temperature distribution in both the upstream and downstream directions of the corridor. The research findings may benefit the design and management of the smoke control system and provide guidance in improving the fire safety level of the commonly existing room-corridor structures.

The special properties of loess make its impact on the vibration propagation of high-speed railways different from other soils. In this study, the static and dynamic characteristics of loess were studied by static and dynamic triaxial tests. The experimental results show that when the frequency is the same, the dynamic stress-strain relationship curve moves up with the increase of the confining pressure. The frequency has little effect on the initial tangential dynamic modulus of the undisturbed loess. we studied the static and dynamic characteristics of loess and discussed the implementation methods of viscoelastic artificial boundary and infinite element boundary in high-speed rail dynamic response analysis. The vibration reduction and isolation effect of the trench with different filling materials (the concrete, gypsum, foamed plastic, and rubber) was studied. The results show that the comprehensive performance of the foamed plastics is better from the perspective of durability and stability of the vibration isolation trench wall. The research results can provide a reference for the selection of filling materials for high-speed railway vibration isolation trench in loess area.

In this study, the typical application of supports and hangers in the water supply and drainage system, ventilation and smoke extraction duct system and electric or optical fiber system has been collected and investigated, in order to understand the fire resistance of supports and hangers used for service installation in China, and further optimize the fire testing and evaluating method of these products. A series of fire resistant testing for supports and hangers used in different working condition have been carried out and the effect of bearing load and structure on the fire resistance of supports and hangers has also been discussed in this paper. Moreover, the improved fire resistant testing and evaluating method has been proposed here.

Although utility tunnels act as an innovative technique for the sustainable development of city’s utilities and limited underground space today, the fire issues in this type of tunnel should be carefully treated as they are different from traffic tunnel fire scenarios. In order to propose an easy-to-use two-dimensional (2D) temperature estimation methodology that is helpful to the designers, operators and firefighters, the temperature distributions and ceiling jet thickness (the vertical distance from the ceiling to where the temperature within the fire-induced smoke flow drops to half of its maximum at a certain location) were investigated with full-scale fire tests in a utility tunnel. The vertical temperature distributions were represented as a normalized single convex-concave profile. Self-similarity was confirmed and three types of similarity profiles were found. In order to correlate the inner boundary layer region and outer region of these ceiling jet flow profiles, a series of mathematical functions combining a power function and Gortler’s error function were employed. Furthermore, the ceiling jet thickness was found to vary as a power function with the longitudinal distance, rather than being a constant as previous research suggested. The vertical distribution model, the ceiling jet thickness model and the longitudinal temperature decay model were combined into a framework to empirically estimate the 2D thermal environment generated by strong fire plumes in utility tunnel’s fire protection engineering practice.

Pedestrian merging behavior is one of the most frequently observed complex pedestrian behaviors and has a certain limited impact on evacuation efficiency in emergency situations. However, experimental research on the multiple merging behavior of pedestrians is very limited. To explore the macroscopic and microscopic characteristics of multiple-merging under special-angle conditions, this paper studies the pedestrian behavior of the main channel and branches in multiple-merging behavior, and analyzes the microscopic and macroscopic characteristics of pedestrians in the case of multiple merging. The width of the main channel is fixed at 2.4[Formula: see text]m, the angle between the branches and the main channel is 30, and the change in the width of the merging branches is 0.8, 1.2 and 1.6[Formula: see text]m. A total of 171 volunteers participated in the experiment, and UWB equipment was used to extract pedestrian trajectories. Obvious lanes were formed during the experiment, and there were obvious ramps. The density of the double branches is significantly higher than that of the single branch, and the maximum saturation value can reach 3.75[Formula: see text]ped/m2. When the width of the branch becomes narrower, the branch entrance and the main channel block each other. When the width of the branch is narrow enough, the influence of the number of branches on the speed of the branch is reduced. When the number of branches increases, to make the distribution of pedestrians more even, the width of the branches also needs to be increased. We also analyzed the headway distance and found that almost all the volunteers in the experiment were under the free system. The results are helpful for correction of the multimerging simulation model and design improvement of the daily multimerging scene.

Liquid air energy storage (LAES) uses air as both the storage medium and working fluid, and it falls into the broad category of thermo-mechanical energy storage technologies. The LAES technology offers several advantages including high energy density and scalability, cost-competitiveness and non-geographical constraints, and hence has attracted a growing interest in recent years. As a result, several reviews have been published on the topic. However, these reviews covered little in the following aspects of LAES: dynamic simulation and optimisation, key components for LAES, LAES applications through integration, and unified economic and cost models for LAES. This article provides a comprehensive review on the LAES technology and fills the above gaps. Apart from applications in electrical grids such as peak-shaving, load shifting, and dealing with intermittency of renewable generation, the review also shows a diverse range of other LAES applications through integration, including waste heat and cold energy recovery and utilisation, multi-energy vector service provision, and sector coupling for chemical production and carbon capture. The review also leads to the recommendation of several areas for future research and development, including dynamic characteristics of whole LAES system integrated with renewables and end users; thermo-economic and dynamic optimization of stand-alone LAES and integrated systems; and experimental study on commercial systems.

This study investigated the burning characteristics of PMMA with varied stretch rates under stagnation-point diffusion flames both theoretically and experimentally, focusing on the manner in which the surface energy balance and heat losses affected burning rate with varied stretch rates. The burning rate versus stretch rate was firstly investigated by introducing a modified Spalding B number, where the burning rate was proved to equal the buoyancy or forced flow induced stretch rate to the power of 0.5. At lower stretch rate, burning was largely affected by heat losses, associated with a lower B number, and decreased up to the quenching limit, similar to the microgravity results. At higher stretch rate, burning was controlled by flame radiation with a larger B number and increased burning rate. Additionally, ice bath increased the solid in-depth conduction heat loss due to the lower temperature maintained at the upper surface of the sample, and further influenced the energy balance with a larger heat losses fraction, leading to reduced B number and burning rate. This study provided an insightful investigation of the burning behaviors of stagnation-point diffusion flames with low stretch rates, which was used in a terrestrial environment to simulate microgravity flames.

In recent years, the measures to interfere the crowds movement with physical facilities (such as channelizing, separation railing) have become more and more common, but how they affect the crowd movement and what moving risks exist in the entrance confluence area have not been fully revealed. Therefore, this paper analyzes the moving risk of the crowds before the bottleneck entrance area, in the presence of the channelizing barriers by controllable laboratory experiments. The visual color cloud charts of the local density, speed and confusion degree of moving directions within the entrance confluence area are analyzed in the presence of different gaps (1.05m and 0.7m) channelizing barriers, to further quantify the motion risk of the crowds. The study finds that the narrower gaps of the channelizing railings, the larger area of high-risk zones, and they have clear ‘lane formation’ effect in shaping the risk zones. The both ends of the channelizing barriers are higher moving risk zones for multi-entry sides conditions, but the area before the middle channels also needs to be closely concerned when the participants entering from two opposite entering sides. The study will provide theoretical basis for evaluating the safety of the setting conditions of the channelizing barriers and conducting scientific crowd management decisions.

The increasing demand for cooling and refrigeration poses an urgent need in designing efficient and low-cost thermal energy storage systems for future energy systems. While multiple effects may affect the heat transfer behaviors during thermal energy storage, these effects can be lumped into one parameter, the effective thermal conductivity. Effective thermal conductivity provides a simple and reliable solution for accurate numerical simulations in designing a thermal energy storage system. In this study, a novel experimental, numerical and Bayesian optimization-based method is developed and validated that allows for fast and accurate measurement of the effective thermal conductivities over a wide temperature range. The method can also be applied to other bulky and heterogeneous structures that cannot be considered as continuous media. An experimental setup and a 3D numerical model were developed for the plate-type thermal energy storage. After a thorough algorithm comparison, Bayesian optimization using Gaussian process was selected to search for the effective thermal conductivities with high accuracy (root mean square error < 2 K and R-squared between 0.975 and 0.992). The effective thermal conductivities measured using deionized water as the phase change material were validated by a COMSOL simulation. With the accurate effective thermal conductivity results, we revealed that neglecting the effective thermal conductivity for the solid phase while still using conduction models will lead to significant errors in the simulation. A duo arch-shaped graphite sheet-based macrofiller is designed and inserted into the plate-type thermal energy storage, which increased the effective thermal conductivities by around 20% and suppressed the subcooling effect. The authors would like to acknowledge the funding support from SJ-NTU Corporate Lab at Nanyang Technological University. This study is supported under the RIE2020 Industry Alignment Fund – Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contribution from Surbana Jurong Pte Ltd. This research is partially funded by the Ministerio de Ciencia Innovacion ´ y Universidades de Espana ˜ (RTI2018-093849-B-C31— MCIU/AEI/FEDER, UE), and the Ministerio de Ciencia, Innovacion ´ y Universidades—Agencia Estatal de Investigacion ´ (AEI) (RED2018- 102431-T). This work is partially supported by ICREA under the ICREA Academia programme.

Tens of millions of abandoned exploitation wells (AEW) exist throughout the world, posing a threat to the environment and costing extra investment for decommissioning. Revitalization of the AEW offers a cost-effective solution for geothermal energy exploitation by saving the high costs of decommissioning and drilling. However, the thermal resources from AEW are usually of low and medium grade. Measures should be taken to increase the efficiency of AEW geothermal power plants. Meanwhile, the regasification process of satellite liquified natural gas (LNG) stations worldwide suffer from a loss of high-grade cold energy. Various studies have used geothermal heat and LNG cold to produce electricity, yet the horizontal extension of the AEW that may increase the recovered temperature, and the fluctuation of the LNG flow that may reduce the power output, were not discussed. This study proposes and evaluates a novel integrated organic Rankine cycle (ORC) system that uses the geothermal heat from the AEWs and waste LNG cold energy from satellite LNG stations, focusing on the performance enhancement of horizontal extension to increase the geothermal temperature and thermal energy storage to stabilize the LNG cold energy supply. A numerical model is developed that considers the horizontal extension in the AEW, and the horizontal extension is found to significantly increase the geothermal fluid temperature. A machine learning-based predictive model is built to assess the AEW outlet temperature under given parameters and working conditions. Cold thermal energy storage (CTES) modules are designed and optimized to stabilize the waste cold energy recovery when exposed to highly fluctuating LNG supply during off-design operation. CTES increased the ORC efficiency by 38.5% and has the potential to significantly shorten the payback period. Therefore, by utilizing the horizontal extension of the AEW and combining the power generation with LNG cold through thermal energy storage, the zero-emission geothermal and waste cold energy-based system can be a viable solution for future AEW revitalization and LNG waste cold energy utilization. This work received financial support from the "Start-up Funding for New Faculty" provided by the Nanjing University of Aeronautics and Astronautics. This study is also supported under the RIE2020 Industry Alignment Fund -Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contributions from Surbana Jurong Pte Ltd. This research is partially funded by the Ministerio de Ciencia Innovacion y Universidades de Espana (RTI2018-093849-B-C31MCIU/AEI/FEDER, UE), and the Ministerio de Ciencia, Innovacion y Universidades-Agencia Estatal de Investigacion (AEI) (RED2018102431-T). This work is partially supported by ICREA under the ICREA Academia program. The authors at the University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537).

This contribution experimentally investigates the heat transfer and the consequent auto-ignition of thermally thick PMMA (polymethyl methacrylate) exposed to linearly declining heat flux (HF) coupling with a theoretically derived model. Thermal decomposition in solid was ignored and critical temperature was utilized. Both scenarios neglecting and considering surface heat loss were studied in the proposed model. An asymptotic solution, extending the derivation method from constant to time-declining heat flux, was obtained to explicitly estimate the surface temperature and ignition time. The credibility of the established model was validated through comparison with experimental data and a previously developed numerical model. The results show that in both considered scenarios ignition is confined in a region where the decreasing rate of heat flux is lower than a critical value. No ignition occurs if the decreasing rate increases beyond this region. The newly developed model is compatible with the correlations of constant heat flux, and it provides identical accuracy in predicting ignition time when compared with other existing models in the literature. A constant surface heat loss coefficient was used in the model, and it was found little error is introduced by invoking this approximation. Also, a parametric study was implemented, indicating that the critical temperature affects the ignition time prediction significantly. Meanwhile, the effects of surface heat loss on surface temperature and ignition time were quantitatively evaluated.

In a car fire, thermal radiation poses a major threat to people and adjacent cars. Thus, estimations of fire safety distances are of great significance for the evacuation assignment and parking lot design. In the present full-scale experiment of a minivan car fire, the left cooling fan in the engine compartment was ignited as the origin of fire. The burn down of front bumper and windows markedly affected the fire intensity in engine and passenger compartment respectively. In the burning process, the peak heat release rate reached maximum value of 3.38 MW when gasoline leaked out. The flame model was assumed to be a superposition of several cuboids for the estimation of view factors of the fire. The average radiative fractions in the intense burning phases of engine and passenger compartments were first determined as 0.469 and 0.589, respectively, based on the burning behavior analysis. The resulting values allowed for the determination of thermal radiation in spatial positions and fire safety distances in the lateral side of the car for people and adjacent cars, which was an extension of previous researches of considering only the thermal radiation in certain positions. The calculation results of thermal radiation were in good agreement with the previous experimental data. The fire safety distances in the lateral direction of the car for people without protection and adjacent cars in this study, as examples, were about 7.3 m and 2.1 m respectively under threshold values of heat fluxes.