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Advancing the prediction of evaporation rate of liquid pool fires in mechanically ventilated compartments using computational fluid dynamics
No full textThe propagation of smoke and hot gases in mechanically ventilated nuclear compartments has been highlighted as one of the main issues of significance. It may lead to the failure of several systems such as clogging of filters located in the ventilation network or electrical devices. To address this issue, the continuous improvement of the predictive capability of existing models with regards to liquid pool fires is of high importance. Computational fluid dynamics (CFD) is widely used for fire simulations. It is worth noting that most pool fire simulations in open atmosphere, under-ventilated and mechanically ventilated compartments have relied on pre-defined/prescribed fuel mass loss rate (MLR) or heat release rates (HRR) from correlations or experimental data when available. Therefore, the prediction of fuel MLR and HRR based on the specific actual fire conditions rather than prescribed data, remains a key development area for the fire community. The present work aims to provide some contribution and advances on this issue. Building on existing liquid evaporation models, the study develops an approach which in then implemented in an in-house version of the CFD code FireFOAM in which a mechanical ventilation model has been embedded, to predict the fuel MLR in both open atmosphere and mechanically ventilated compartments. Validations of the implemented model includes comparison with experimental fuel MLR and previous studies that made use of correlations and experimental data. The results show acceptable fuel MLR predictions with reasonable accuracy and provide further insights into fire behaviour in mechanically ventilated compartments
A comprehensive survey of Federated Intrusion Detection Systems : techniques, challenges and solutions
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Bioinspired double-layer thermogalvanic cells with engineered ionic gradients for high-efficiency waste heat recovery
No full textThermogalvanic cells (TGCs) have emerged as a promising technology for harvesting low-grade thermal energy, but their widespread application has been hindered by limited conversion efficiencies. A critical factor in enhancing TGC performance lies in establishing substantial ion concentration gradients, which remains challenging due to the inherent tendency of ion pairing. Here, we present a breakthrough double-layer thermogalvanic cell (DTGC) architecture that spatially segregates redox pairs into two distinct gel layers, enabling unprecedented control over ion concentration gradients. This innovative design yields a single p-type gelatin-K4[Fe(CN)6]/K3[Fe(CN)6] DTGC unit with remarkable performance metrics of an open-circuit voltage of 220 mV, a power density of 1.73 mW m-2 K-2, and a relative Carnot efficiency (ηr) of 1.34% at ΔT = 10 K, representing a tenfold improvement over conventional TGCs. Scaling up this technology, we demonstrate a modular thermoelectric generator comprising a 4×12 array of alternating p-type and n-type DTGCs, capable of delivering an output voltage exceeding 11.3 V at ΔT = 20 K, sufficient to directly power commercial LED lights and electronic displays. This work establishes a new paradigm for efficient low-grade thermal energy conversion, offering a scalable and practical solution for waste heat recovery applications
Hydrothermal carbonisation products energy properties : the role of digested sludge type and operating conditions
No full textHydrothermal carbonization (HTC) is a promising alternative to conventional sludge drying, enhancing energy recovery in wastewater treatment plants (WWTPs). This study examines how temperature, residence time, and sludge collection point influence HTC product properties. Experiments were conducted at 200–250 °C for 30–120 min using digested sludge collected before filtration, after thickening, and after dewatering. Results show that sludge collection point strongly affects hydrochar’s higher heating value (HHV), while temperature and residence time influence the biomethane potential (BMP) of HTC liquids. The highest HHV (16.31 MJ/kg) was obtained from dewatered sludge (19.8 % TS) at 250 °C, 75 min, while the highest BMP (506 mlCH4/g NPOC) was observed from HTC liquids of thickened sludge (11.1 % TS) at 200 °C, 30 min. Findings highlight that sludge pre-treatment (thickening, dewatering) plays a crucial role in HTC efficiency, influencing both solid and liquid fractions. From a WWTP perspective, dewatered sludge processed under mild HTC conditions provides the best trade-off between hydrochar quality, HTC liquid valorization, and operational costs. These insights support the optimization of sludge-to-energy strategies, essential for implementing HTC in WWTPs
How AI is making affordable air pollution sensors more accurate
No full textClean air is a fundamental right. However, every day, 100 children under the age of five tragically lose their lives in east Asia and the Pacific due to a silent killer – air pollution. In response to this crisis, huge investments have been made in outdoor air pollution monitoring systems. These fridge-sized monitoring stations are expensive costing at least £10,000 each, so scaling this up everywhere isn’t financially viable. Now, a new generation of small, roaming air sensors could better inform people about pollution levels in their local area. Currently, these sensors just aren’t precise enough. Our recent research shows that AI could enhance their accuracy by up to 46%
Developing empathy for diversity through a narrative of activism
No full textDiscover how empathy can reshape educational spaces in this episode, inspired by the transformative power of storytelling. We highlight the lived experiences of activists and explore how real-world narratives can break down barriers, challenge systemic injustices, and cultivate inclusive learning environments. Tune in to learn how educators can foster empathy, promote social justice, and ignite actionable change both in and beyond the classroom
Hydrothermal carbonization of digested sludge from wastewater treatment plants : processes, potential and key challenges
No full textThe presentation reviews hydrothermal carbonization of digested sludge as a complementary technology for sludge management at wastewater treatment plants. The motivation for expanding the knowledge of hydrothermal carbonization is the challenges of wastewater treatment plants: the increasing volume of sludge, high moisture content, the presence of organic and inorganic contaminants, rising disposal costs, and legislative amendments. Hydrothermal carbonization makes it possible to convert wet sludge under conditions (160–250 °C,10–30 bar) into hydrophobic hydrochars, but also liquids and gases, eliminating the need for drying. The process also offers heat recovery and integration into existing wastewater treatment plant infrastructure. A key aspect of implementing hydrothermal carbonization is understanding the impact of individual process parameters and their interactions on chemical reaction pathways, and optimizing operating conditions for specific applications. The presentation discusses two pathways for hydrochar utilization: as soil additives or as fuels in thermal processes, assessing their environmental and legal potential. Process liquids were evaluated as a source of valuable resources that can be recovered or used in situ. Despite the compatibility of hydrothermal carbonization with Green Deal policies, challenges related to energy efficiency, legislative compliance, public acceptance, and high investment costs for integrated thermal technologies still need to be addressed. Overcoming these barriers will enable the implementation of hydrothermal carbonization as a sustainable technology in a circular economy