ORCID Profile
0000-0002-6364-1898
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Publisher: MDPI AG
Date: 09-04-2019
DOI: 10.3390/APP9071486
Abstract: The steam ejector is a core component of an ejector-based refrigeration system. Additionally, steam ejectors can also be potentially applied for a fire suppression system by using pressurized steam droplets to rapidly quench and extinguish the fire. The use of steam will significantly reduce the amount of water consumption and pipe flow rate compared to conventional sprinklers. However, the efficiency of the steam ejector nozzle is one of major factors that can influence the extinguishing mechanisms and the performance of pressurized steam for fire suppression. In this article, to formulate an assessment tool for studying the ideal entrainment ratio and initial flow wetness, a wet steam model has been proposed to enhance our understanding of the condensation and evaporation effects of water droplets from a numerical perspective. The entire steam-ejector system including the nozzle, mixing chamber, throat and diffuser were modeled to study the profiles in axial pressure and temperature across the system, and were compared with self-measured experimental data. In addition, the flow and heat transfer interactions between the fluid mixture and nucleating water droplets were numerically examined by comparing initial conditions with different liquid fractions, as opposed to the ideal gas assumption. With the application of the proposed wet-steam model, the numerical model showed vast improvement in the axial pressure distribution over the ideal gas model. Through numerical conditions, it was found that reducing the wetness of the secondary inlet flow will potentially optimize the system performance with a significant increase of the entrainment ratio from 0.38 to 0.47 (i.e., improvement of around 23%).
Publisher: MDPI AG
Date: 03-06-2019
Abstract: Fabricating high-performance MXene-based polymer nanocomposites is a huge challenge because of the poor dispersion and interfacial interaction of MXene nanosheets in the polymer matrix. To address the issue, MXene nanosheets were successfully exfoliated and subsequently modified by long-chain cationic agents with different chain lengths, i.e., decyltrimethylammonium bromide (DTAB), octadecyltrimethylammonium bromide (OTAB), and dihexadecyldimethylammonium bromide (DDAB). With the long-chain groups on their surface, modified Ti3C2 (MXene) nanosheets were well dispersed in N,N-dimethylformamide (DMF), resulting in the formation of uniform dispersion and strong interfacial adhesion within a polystyrene (PS) matrix. The thermal stability properties of cationic modified Ti3C2/PS nanocomposites were improved considerably with the temperatures at 5% weight loss increasing by 20 °C for DTAB-Ti3C2/PS, 25 °C for OTAB-Ti3C2/PS and 23 °C for DDAB-Ti3C2/PS, respectively. The modified MXene nanosheets also enhanced the flame-retardant properties of PS. Compared to neat PS, the peak heat release rate (PHRR) was reduced by approximately 26.4%, 21.5% and 20.8% for PS/OTAB-Ti3C2, PS/DDAB-Ti3C2 and PS/DTAB-Ti3C2, respectively. Significant reductions in CO and CO2 productions were also obtained in the cone calorimeter test and generally lower pyrolysis volatile products were recorded by PS/OTAB-Ti3C2 compared to pristine PS. These property enhancements of PS nanocomposites are attributed to the superior dispersion, catalytic and barrier effects of Ti3C2 nanosheets.
Publisher: MDPI AG
Date: 18-01-2021
DOI: 10.3390/MOLECULES26020478
Abstract: In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery systems has always been a global concern for the end-users. The separator is an indispensable part of lithium-ion batteries since it functions as a physical barrier for the electrode as well as an electrolyte reservoir for ionic transport. The properties of separators have direct influences on the performance of lithium-ion batteries, therefore the separators play an important role in the battery safety issue. With the rapid developments of applied materials, there have been extensive efforts to utilize these new materials as battery separators with enhanced electrical, fire, and explosion prevention performances. In this review, we aim to deliver an overview of recent advancements in numerical models on battery separators. Moreover, we summarize the physical properties of separators and benchmark selective key performance indicators. A broad picture of recent simulation studies on separators is given and a brief outlook for the future directions is also proposed.
Publisher: Elsevier BV
Date: 12-2022
Publisher: MDPI AG
Date: 30-01-2019
DOI: 10.3390/FIRE2010007
Abstract: In this study, a Large Eddy Simulation (LES) based fire field model was applied to numerically investigate the effectiveness of smoke control using smoke vents and curtains within a large-scale atrium fire. Two compartment configurations were considered: the first case with no smoke curtains installed, while the second case included a smoke curtain at the centre of the compartment to trap smoke. Based on the thermocouple results, it was found that the model predicted the gas temperature near the fire particularly well. The time development and heat transfer of the gas temperature predictions were in good agreement with the experimental measurements. Nevertheless, the gas temperature was slightly under-predicted when the thermocouple was further away from the flaming region. Overall, it was discovered that the combination of a smoke curtain and ceiling vents was a highly effective natural smoke exhaust system. However, under the same vent configuration, if the smoke curtain height is not adequate to completely block the spread of smoke, it significantly reduces the pressure differential between the compartment and the exterior, causing reduced flow rates in the outlet vents.
Publisher: Elsevier BV
Date: 2023
Publisher: MDPI AG
Date: 02-06-2023
DOI: 10.20944/PREPRINTS202306.0115.V1
Abstract: To date, zinc ion batteries (ZIBs) have been attracting extensive attention due to their outstanding properties and the potential to be the solution for next-generation energy storage systems. However, the uncontrollable growth of zinc dendrites and water-splitting issues seriously restrict the further scalable application. Over the past few years, solid polymer electrolytes (SPEs) have been regarded as a promising alternative to address these challenges and facilitate the practical advancement of zinc batteries. In this review, we revisited the research progress of SPEs applied in zinc batteries in the past few years and focus on introducing cutting-edge polymer science and technologies that can be utilized to prepare advanced SPEs for high-performance zinc batteries. The operating mechanism of SPEs and the functions of polymers will be summarized. To highlight the polymer functions, SPEs are categorized into three types, respectively, homogenous polymer SPEs, hybrids polymer SPEs, and nanocomposites SPEs, which are expected to reveal the roles and principles of various polymers in zinc batteries. This review presents the current research progress and fundamental mechanisms of polymer-based SPEs in zinc batteries, outlines the challenging issues encountered, and meanwhile proposes potential solutions for future endeavours.
Publisher: Elsevier BV
Date: 05-2022
Publisher: MDPI AG
Date: 27-06-2023
Abstract: To date, zinc-ion batteries (ZIBs) have been attracting extensive attention due to their outstanding properties and the potential to be the solution for next-generation energy storage systems. However, the uncontrollable growth of zinc dendrites and water-splitting issues seriously restrict their further scalable application. Over the past few years, solid polymer electrolytes (SPEs) have been regarded as a promising alternative to address these challenges and facilitate the practical advancement of zinc batteries. In this review, we revisit the research progress of SPEs applied in zinc batteries in the past few years and focus on introducing cutting-edge polymer science and technologies that can be utilised to prepare advanced SPEs for high-performance zinc batteries. The operating mechanism of SPEs and the functions of polymers are summarised. To highlight the polymer’s functions, SPEs are categorised into three types, homogenous polymer SPEs, hybrids polymer SPEs, and nanocomposites SPEs, which are expected to reveal the roles and principles of various polymers in zinc batteries. This review presents the current research progress and fundamental mechanisms of polymer-based SPEs in zinc batteries, outlines the challenging issues encountered, and proposes potential solutions for future endeavours.
Publisher: Wiley
Date: 08-04-2021
DOI: 10.1002/FAM.2973
Abstract: Multifunctional building façades have become an increasingly critical component in modern buildings, especially after the tremendous scrutiny triggered by the utilization of combustible aluminum cladding panels (ACP) in the construction sector. Following the massive effort by both industry and government agencies to reduce the fire risks of combustible façades in recent years, façades with insufficient fire ratings have been continuously causing severe building fires leading to countless human casualties and properties damages. This review aims to provide an in‐depth overview of the previous developments and current progress for establishing relevant fire standards with regards to ACPs, from an Australian standpoint. The fire spread mechanisms associate with ACPs, and their potential hazards were discussed. Furthermore, the current building regulations for ACPs have been reviewed, including detailed experimental procedures and rating criterion for all existing international standards. To address the research knowledge gap in terms of the understanding of the cladding fire mechanisms, and combustibility of existing ACP polymer composites, recent advancement in experimental and numerical studies has been summarized and discussed to identify the critical issues and concerns for current ACP products. Future perspectives involving cutting‐edge approaches such as computational fluid dynamics (CFD) modeling coupled with artificial neural network (ANN) optimization are advocated in this article. Additionally, fundamental material characterization techniques using molecular dynamics (MD) approaches can be implemented to deliver a better description of the degradation kinetics and smoke/toxicity generations.
Publisher: MDPI AG
Date: 16-06-2023
DOI: 10.3390/MI14061260
Abstract: Micro-cooling systems are compact refrigeration systems widely applicable in microchemical analysis, biomedicine, and microelectromechanical systems (MEMS). These systems rely on the use of micro-ejectors to achieve precise, fast, and reliable flow and temperature control. However, the efficiency of micro-cooling systems is hindered by spontaneous condensation occurring downstream of the nozzle throat and within the nozzle itself, impacting the performance of the micro-ejector. A micro-scale ejector mathematical model describing wet steam flow was simulated to investigate the steam condensation phenomenon and its influence on flow, incorporating equations for liquid phase mass fraction and droplet number density transfer. The simulation results of wet vapor flow and ideal gas flow were compared and analyzed. The findings revealed that the pressure at the micro-nozzle outlet exceeded predictions based on the ideal gas assumption, while the velocity fell below it. These discrepancies indicated that condensation of the working fluid reduces the pumping capacity and the efficiency of the micro-cooling system. Furthermore, simulations explored the impact of inlet pressure and temperature conditions on spontaneous condensation within the nozzle. The results demonstrated that the properties of the working fluid directly influence transonic flow condensation, underscoring the importance of selecting appropriate working fluid parameters for nozzle design to ensure nozzle stability and optimal micro-ejector operation.
Publisher: Elsevier BV
Date: 09-2022
Publisher: MDPI AG
Date: 13-10-2022
DOI: 10.3390/FIRE5050165
Abstract: In this article, a collective database from validated numerical simulation has been established to study the suppression effects of water-based suppression systems under a single-compartment fire scenario at various suppression configurations and fire locations. Five fuel locations along the axis between the centre and corner of the room were configurated to dynamically analyse how the horizontal distance between the nozzle and fuel pan affects the heat release rate (HRR), temperature cooling phenomena at different heights and also the velocity profile. Throughout the fuel pan relocations, the water-mist system has achieved an average suppression time of 25 s for all the locations, it was found that the water mist system can effectively control the fire under 200 °C that is distanced over 2 m spanwise displacement from the nozzle against the fire, while the sprinkler has exhibited an excellent fuel surface cooling effect due to large momentum and heat capacity within the coverage area with an average suppression time of 50 s. The results of this study have further explored the spray coverage and droplet penetrability of different suppression systems at different locations corresponding to the fire source, and the quantitative assessment of fuel locations could also contribute to the future development of performance-based fire safety designs.
Publisher: CRC Press
Date: 20-06-2023
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 05-2020
Publisher: MDPI AG
Date: 04-11-2022
Abstract: With the increasing demand for energy capacity and power density in battery systems, the thermal safety of lithium-ion batteries has become a major challenge for the upcoming decade. The heat transfer during the battery thermal runaway provides insight into thermal propagation. A better understanding of the heat exchange process improves a safer design and enhances battery thermal management performance. This work proposes a three-dimensional thermal model for the battery pack simulation by applying an in-house model to study the internal battery thermal propagation effect under the computational fluid dynamics (CFD) simulation framework. The simulation results were validated with the experimental data. The detailed temperature distribution and heat transfer behaviour were simulated and analyzed. The thermal behaviour and cooling performance were compared by changing the abnormal heat generation locations inside the battery pack. The results indicated that various abnormal heat locations disperse heat to the surrounding coolant and other cells. According to the current battery pack setups, the maximum temperature of Row 2 cases can be increased by 2.93%, and the temperature difference was also increased. Overall, a new analytical approach has been demonstrated to investigate several stipulating battery thermal propagation scenarios for enhancing battery thermal performances.
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.JHAZMAT.2019.04.026
Abstract: Thermoplastic polyurethane (TPU) has broad applications as lightweight materials due to its multiple advantages and unique properties. Nevertheless, toxicity emission under fire conditions remains a major concern, particularly in building fire scenarios. To circumvent the problem, it is imperative that an effective flame retardant is sought to suppress the flame and release of combustion/smoke products whilst maintaining the favorable material properties of TPU. In the current work, a simple method is proposed for the preparation and utilization of cetyltrimethyl ammonium bromide (CTAB) and tetrabutyl phosphine chloride (TBPC) modified Ti
Publisher: Elsevier BV
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 19-06-2021
Publisher: Springer Science and Business Media LLC
Date: 10-06-2019
Publisher: MDPI AG
Date: 09-11-2022
DOI: 10.3390/E24111625
Abstract: The steam ejector is valuable and efficient in the fire suppression field due to its strong fluid-carrying capacity and mixing ability. It utilizes pressurized steam droplets generated at the exit to extinguish the fire quickly and the steam droplet strategy allows for an expressive decrease in water consumption. In this regard, the fire suppression process is influenced by the steam ejector efficiency, the performance of the pressurized steam, and the ejector core geometry, which controls the quality of the extinguishing mechanisms. This study investigated the impact of different mixing section diameters on the pumping performance of the ejector. The results showed that change in the diffuser throat diameter was susceptible to the entrainment ratio, which significantly increased, by 4 mm, by increasing the throat diameter of the diffuser and improved the pumping efficiency. Still, the critical back pressure of the ejector reduced. In addition, the diameter effect was studied and analyzed to evaluate the ejector performance under different operating parameters. The results revealed a rise in the entrainment ratio, then it diminished with increasing primary fluid pressure. The highest entrainment ratio recorded was 0.5 when the pressure reached 0.36 MPa at the critical range of back pressure, where the entrainment ratio remained constant until a certain back pressure value. Exceeding the critical pressure by increasing the back pressure to 7000 Pa permitted the entrainment ratio to reduce to zero. An optimum constant diameter maximized the ejector pumping efficiency under certain operating parameters. In actual design and production, it is necessary to consider both the exhaust efficiency and the ultimate exhaust capacity of the ejector.
Publisher: MDPI AG
Date: 08-07-2022
Abstract: The increasing popularity of lithium-ion battery systems, particularly in electric vehicles and energy storage systems, has gained broad research interest regarding performance optimization, thermal stability, and fire safety. To enhance the battery thermal management system, a comprehensive investigation of the thermal behaviour and heat exchange process of battery systems is paramount. In this paper, a three-dimensional electro-thermal model coupled with fluid dynamics module was developed to comprehensively analyze the temperature distribution of battery packs and the heat carried away. The computational fluid dynamics (CFD) simulation results of the lumped battery model were validated and verified by considering natural ventilation speed and ambient temperature. In the artificial neural networks (ANN) model, the multilayer perceptron was applied to train the numerical outputs and optimal design of the battery setup, achieving a 1.9% decrease in maximum temperature and a 4.5% drop in temperature difference. The simulation results provide a practical compromise in optimizing the battery configuration and cooling efficiency, balancing the layout of the battery system, and safety performance. The present modelling framework demonstrates an innovative approach to utilizing high-fidelity electro-thermal/CFD numerical inputs for ANN optimization, potentially enhancing the state-of-art thermal management and reducing the risks of thermal runaway and fire outbreaks.
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.JHAZMAT.2019.120952
Abstract: MXene/chitosan nanocoating for flexible polyurethane foam (PUF) was prepared via layer-by-layer (LbL) approach. MXene (Ti
Publisher: Elsevier BV
Date: 12-2014
Publisher: American Chemical Society (ACS)
Date: 31-10-2018
Abstract: A novel three-dimensional (3D) epoxy/graphene nanosheet/hydroxylated boron nitride (EP/GNS/BNOH) hybrid aerogel was successfully fabricated in this study. This was uniquely achieved by constructing a well-defined and interconnected 3D network architecture. The manufacturing process of EP/GNS/BNOH involved a simple one-pot hydrothermal strategy, followed by the treatment of freeze-drying and high-temperature curing. In comparison with EP/GNS-3, EP/GNS/BNOH-3 demonstrated improvement of 97% for compressive strength at 70% strain. Through compression tests, fracture occurred for EP/GNS-3 at ninth compression cycles, whereas EP/GNS/BNOH-3 retained its original form after twenty compression cycles, with a residual height of 97% (i.e., only 3% reduction). By the addition of BNOH in the polymer matrix, the dynamic heat transfer and dissipation rates of EP/GNS/BNOH aerogels were also considerably reduced, indicating that the aerogel with BNOH additive possessed excellent thermal insulation properties. Thermogravimetric analysis results revealed that the thermal stabilities of EP/GNS and EP/GNS/BNOH aerogels were improved with increasing loading of EP, and EP/GNS/BNOH aerogels exhibited a better thermal stability at high temperatures. Through the elevated levels attained in the compressive strength, superelasticity, and thermal resistance, EP/GNS/BNOH aerogels has the great potential of being a very effective thermal insulation material to be utilized across a board range of applications in building, automotive, spacecraft, and mechanical systems.
Publisher: Elsevier BV
Date: 11-2021
No related grants have been discovered for Ao Li.