Fire and Materials最新文献

Data center fires, often caused by continuous high-load operations, result in significant losse. Liquid nitrogen has been proposed as an environmentally friendly cryogenic fluid for data center fire prevention. In this work, the effects of liquid nitrogen on typical integrated circuit chips in data centers were studied through experimental research and numerical simulation, focusing on the environmental parameter characteristics and the effects on structural and electrical performance under the liquid nitrogen actions. Results show that liquid nitrogen spraying has obvious cooling and inerting effects. Numerical simulations revealed that the temperature near the action point under spraying decreases to 0°C at 2.5 s at room temperature, indicating significant local cooling. Under high-temperature combustion conditions, the temperature near the action point decreased to 28°C after 21 s, and the oxygen concentration in the experimental space fell below 5% after 60s, effectively inhibiting combustio. The actions of liquid nitrogen have less harmful effect on the chips, with primary impacts observed in some chips and plastic laminates. In addition, because of the poor temperature change characteristics of quartz, the input and output frequencies of the quartz oscillator are unstable, leading to slight deviations in the IV curve. This work provides valuable insights for the development and application of liquid nitrogen fire prevention technology in data centers, offering a critical reference for enhancing fire safety in such environments.

The European project “European Approach to Assess the Fire Performance of Facades” led by RISE, has been working toward the development of a harmonized European testing and assessment method for façade. In this study, we present numerical predictions of the thermal exposure on a noncombustible façade in the European test. Fire Dynamics Simulator (FDS), version 6.7.9, was employed as numerical model. The temperature inside the combustion chamber was underestimated by approximately 8.9%. The heat flux from the wood crib aligns well with the test results up to around 800 s, after which a deviation was observed, likely due to the way the wood crib was modeled. The heat flux at 1 m above the chamber opening was underestimated by 22.2%, while the plate thermometer temperature at the center of the fictitious window was underestimated by 17.6%. The overall trends along the vertical centerline were captured correctly, though overestimations were observed at most locations, except at 1 and 1.5 m above the chamber, with a maximum overestimation of 17.5% at 4.5 m above the chamber. The flame height was determined based on the predicted temperature, with an overestimation of 29.8%. However, this comparison has inherent limitations, primarily due to differences in the methods used to define the flame tip in experimental tests and numerical simulations. An analysis was conducted to assess the influence of the wood crib model on the fire dynamics in this large-scale test.

To promote sustainability, this study incorporates coarse recycled aggregate (RA) from crushed concrete blocks into high-performance concrete (HPC) to reduce the cost of expensive mineral components and reduce surface flaking and thermal degradation at elevated temperatures. Steel fibers (SF) and nano-silica (NS) were introduced as co-modifying agents to enhance HPC's mechanical and microstructural properties. In total, 36 mixtures with varying proportions were designed and subjected to compressive, splitting tensile, and modulus of elasticity tests, considering different RA replacement rates, SF contents, and NS contents. Microstructural analyses, including SEM, XRD, pore distribution, and thermal conductivity tests, were also conducted. Results revealed that SF and NS significantly improved the residual compressive and splitting tensile strengths of HPC with RA (HPC-RA) at elevated temperatures. As temperature increased, residual compressive strength initially rose but then declined, while splitting tensile strength showed a continuous decrease. SEM and XRD analyses confirmed that NS enhanced C-S-H gel formation, improving heat resistance. However, at 600°C, dehydration and C-S-H decomposition led to strength reduction. Pore analysis indicated that higher RA replacement rates introduced more detrimental pores, impacting thermal conductivity. A linear relationship between compressive and splitting tensile strengths was established, along with a temperature-dependent fitting equation to predict residual properties.

This paper investigated a slag composite high-efficiency fire extinguishing material to recycle power plant slag waste and apply it to prevent and control spontaneous coal combustion fires. The composite uses power plant slag as a base material, sodium carboxymethyl cellulose (CMC) as a polymer, and AlCit solution formulated with polyaluminum chloride and citric acid as a cross-linking agent. X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze slag composition and morphology. Experiments investigated the effects of composites on coal microactive groups, rheological properties, and inhibition characteristics against coal spontaneous combustion. Analyses showed composites could effectively reduce activities of aromatic hydrocarbons, OH groups, aliphatic hydrocarbons, and oxygenated functional groups in coal samples, with prominent inhibition of oxygenated functional groups and OH reactive groups. Experimental results showed composite samples exhibited a shear thinning phenomenon of yield-pseudoplastic fluid, and viscosity gradually increased with time. Viscosity increase rates of samples were 9.20%, 17.35%, and 30.75% for each 5-min interval. Composites could delay the time when coal samples enter the rapid oxidation stage, and the crossing point temperature of coal samples increased from 152°C to 180°C. Composites had an inhibitory effect on coal oxygen reaction, and in programmed warming experiments, the temperature at which the residual mass of coal samples began to increase increased from 179°C to 202°C. The slag composite high-efficiency fire extinguishing material provides reference value for the combination of slag waste and mine fire extinguishing technology.

The need for flame-retardant materials with good mechanical properties is rapidly growing across numerous sectors, such as construction, automobile, and aerospace industries. In this research, a comprehensive study has been conducted focusing on flame retardant and mechanical characteristics of distinct resin-based fiber-reinforced composites. Glass and sisal fiber-based woven fabrics have been used as reinforcements in four different types of resin matrices, such as epoxy, vinyl ester, unsaturated polyester, and phenolic resins. The developed composites were systematically evaluated for their flame-retardant properties using limiting oxygen index (LOI), vertical flammability, and cone calorimetry tests, with a focus on assessing the inherent flame resistance of the resins without the incorporation of flame-retardant additives. In parallel, the mechanical behavior of the composites was examined through tensile and flexural testing to determine the combined effects of fiber type and resin matrix. The findings demonstrate that different resin-based composites provide an optimal balance between flame retardancy and mechanical strength, making them suitable for applications requiring both fire safety and structural reliability. The insights gained from this research contribute to the development of new composite materials with enhanced fire performance without compromising mechanical performance.

The complexity of urban tunnel structure increases the risk of tunnel fire, and the air curtain system plays an important role in controlling the spread of fire smoke and ensuring the safety of personnel. Based on theoretical analysis and tunnel model experiments, the isolation effect of different air curtain jet conditions on high-temperature fire smoke in bifurcated tunnel was studied. The results show that the air curtain system can effectively isolate the high-temperature smoke. For different firepower, compared to angle and thickness, wind speed has the best control effect on high-temperature smoke. The control effect of air curtain thickness takes second place. The effect of angle change is the least obvious. Meanwhile, based on the analysis of experimental results, it was found that when the air curtain parameters are selected as wind speed of 2.5 m/s, angle of 15°, and thickness of 0.16 m, the air curtain system has better smoke prevention efficiency. Finally, dimensionless analysis yielded a power law equation relating upstream temperature rise, firepower, and wind speed. This supports theoretically analyzing the air curtain's smoke prevention effect.