An exploration of enhancing thermal protective clothing performance by incorporating aerogel and phase change materials

Thermal liners play a critical role in thermal protective performance for firefighter gear. Effective engineering of textile material is necessary to enhance this protective performance. A modified thermal protective erformance (TPP) tester was used to study the influence of incorporating aerogel and microencapsulated phase change materials (MPCMs) in thermal liners (including a traditional thermal liner, phase‐change layer, and aerogel layer) and the relevant parameters associated with enhanced thermal liner performance. Two different phase‐transition temperature (45°C and 50°C) of MPCM were selected. The samples were exposed to a medium intensity radiation of 15 kW/m² for 240 seconds, and a skin burn model was applied for second‐degree burn prediction. Given the selected, results showed that the best TPP in this study was achieved when the phase‐transition temperature of MPCM was 45°C and the layering order consisted of the traditional thermal layer (closest to heat source), followed by an aerogel layer, and a final MPCM layer. The predicted second‐degree burn time was 218.3 seconds and increased by 90% compared with only containing traditional thermal liner with a thickness of 5 mm. For all 3 materials contained in the thermal liner, the relationship between absorbed energy and predicted second‐degree skin burn time indicated that they had a remarkable negative linear correlation (R² was 0.9792). The experimental data and predicted results were in good agreement, with a correlation coefficient (R²) of 0.9911. The findings provide a scientific basis for future textile engineering and a novel approach to improve TPP.     

Development of a multi‐layered skin simulant for burn injury evaluation of protective fabrics exposed to low radiant heat

To simulate temperature rise of human skin and to predict burn injury during radiant heat exposure, the traditional method is to use a sensor to simulate skin surface and use a numerical model to simulate heat transfer in inner skin. However, the numerical models of skin burns are based on few experimental data of nude skin and some simplifications of human skin characteristics. In this study, a new multi‐layered skin simulant is presented for low radiant heat exposures up to 15 kW/m². The skin simulant has implanted thermocouples into layered polydimethylsiloxane (PDMS) materials with controlled thermal properties and thicknesses of the skin layers. The multi‐layered skin simulant developed in this study has a good reproducibility for temperature measurements with similar temperature rise profiles compared with human skin except at skin surface. For burn injury prediction, the results of our PDMS skin model can be linearly corrected using ASTM model as a reference. Our developed skin simulant provides an advanced method to directly simulate the heat transfer inside human skin in a multi‐layered structure rather than using the combined physical sensor‐numerical model in the traditional way.     

Comparison of thermal protective performance of aluminized fabrics of basalt fiber and glass fiber

Rapid progress has been made in the field of fire protection during the past few decades, nevertheless, the development of fire protective clothing with prolonged durability has always been a matter for public attention. In order to prevent or minimize skin burn damage resulting from flashover, a kind of thermal protective composite fabric, the surface of which is aluminized, has been upgraded and developed. Using the UV–Vis–NIR (ultraviolet–visible–near infrared) spectrophotometer, the thermal radiation protective performance of aluminized fabrics made of basalt fiber and glass fiber were evaluated and compared. The aluminized fabrics and the substrate fabrics used were exposed to a fire environment generated by burning liquified gas for a few minutes, aiming at evaluating the protective effect of the aluminum coating and characterizing the thermal insulating performance. The results showed that the spectral reflectance of aluminized fabrics present obvious differences over a wide range of wavelengths, perhaps due to the different yarn parameters and weave structure. The fire exposure experiment indicated that the aluminized fabric of basalt fiber had better thermal protective performance than the substrate fabrics. Although the thermal insulating performance of aluminized fabrics is insufficient to provide enough time for people to focus on his/her job, the aluminized fabrics exhibit great potential application in the fields of firefighting and military. Copyright © 2010 John Wiley & Sons, Ltd.     

A quantitative method to compare the effect of thermal aging on the mechanical performance of fire protective fabrics

A method has been proposed to provide a means to compare in a quantitative and comprehensive way the mechanical performance of fire protective fabrics under long-term thermal exposure. These high-performance materials experience a reduction in their performance overtime due to the various conditions they are exposed to during the lifetime of the clothing. The proposed method consists in a system of two equations fitting the time–temperature-performance data: the Arrhenius model combined with the time–temperature superposition principle, and the three-parameter Hill equation. The result of the data analysis using this method is provided in terms of four parameters: the temperature effect, the time rate, the degradation midpoint time, and the ultimate strength. It was used to compare the effect of accelerated thermal aging on the tear strength of seven different fabrics used in fire protective clothing. In all cases, a very good agreement was observed with both the Arrhenius model and the Hill equation. However, none of the fabrics studied appeared to stand as displaying all the characteristics that would be ideal for long-term fire protection. The best solution is thus a compromise that will depend on the type of activity conducted and the type of conditions experienced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47045.     

Simulating the thermal response of the flame manikin with different materials exposed to flash fire by CFD

To investigate the differences of thermal response between heat flux sensors and human skin on the flame manikin, a three‐dimensional heat transfer model was developed and validated by the flame manikin system. The initial temperature of the model with sensor material was set to 300 K, and the model with skin material was set as the real condition. Simulated results validated the effectiveness of heat flux measured by the sensor. The incident heat flux through the measured surface was influenced by the different emissivity of the human skin and experimental sensors. Significant difference was found for the temperature response of these two kinds of materials within 4‐s fire exposure. The heat flux measured by sensor or the simulated results with actual human skin parameters could be used as the input boundary condition of the skin heat transfer model for Henriques's skin burn prediction. It is necessary to study the actual skin thermal response by experiments, where the 3D model established in this study could be used as the supplementary means for skin simulant sensor development. These findings will also be adopted in our following study of skin burn prediction module in the 3D full‐scale simulation platform. Copyright © 2016 John Wiley & Sons, Ltd.     

The study of coupling effects of humidity-heat on the protection performance of protective clothing for fire fighting

The coupling effects of humidity-heat on the thermal protective performance of protective clothing play an important role during the fire fighting process. The thermal stability, heat release, and thermal protective performance of protective clothing were investigated under the coupling effects of humidity-heat condition. The cone calorimeter and the thermogravimetric analysis (hereinafter referred to as TGA) were adopted to investigate the thermal stability and heat release characteristics of protective clothing. The thermal protective performance tester and heat flux meter 8 (hereinafter referred to as HFM-8) multichannel heat flow meter were adopted to simulate the multiple effects of internal sweating, external water spray and high thermal radiation. As for the thermal protective performance experiment (hereinafter referred to as TPP) results, it is found that the proper moisture content can significantly enhance the thermal protective performance, but the performance is seriously degraded after soaking, which is due to the improved thermal conductivity. The mechanism of microscopic changes of protective clothing were also investigated by hot-stage polarizing microscope and scanning electron microscope. The results of this experiment have important practical guiding significance for the safety protection of firefighters during the fire extinguishing processes.     

新型干法水泥窑系统热工性能反求方法与应用

反求工程是指对已经投入运行并证明效果良好的新产品、新技术、新工艺等进行全面、系统、深入的检测、计算与分析,找出其技术关键和控制方法。以一条运行效果良好的5000t／d熟料生产线为研究对象,介绍了新型干法水泥窑系统热工性能反求方法,并对反求结果进行分析,提出了旋风筒分离效率、系统总换热效率、旋风筒各部风速等重要参数范围。     

涤纶膨体长丝热卷曲伸长率的静态测试方法

介绍了一种适用于涤纶膨体长丝(BCF)热卷曲伸长率的静态测试方法。参照FZ/T 54001—2012《丙纶膨体长丝(BCF)》行业标准中热卷曲伸长率的试验方法,采用自制测长装置,通过优选烘箱温度及加热时间,提出了既简便又适用于涤纶BCF热卷曲伸长率的测试方法。     

A new fragment contribution‐corresponding states method for physicochemical properties prediction of ionic liquids

A new fragment contribution‐corresponding states (FC—CS) method based on the group contribution method and the corresponding states principle is developed to predict critical properties of ionic liquids (ILs). There are 46 fragments specially classified for ILs considering the ionic features of ILs, and the corresponding fragment increments are determined using the experimental density data. The accuracy of the developed method is verified indirectly via predicting density and surface tension of ILs. The results show that the FC—CS method is reasonable with an average absolute relative deviation less than 4%. With the calculated critical properties, corresponding states heat capacity (CSHC) and corresponding states thermal conductivity (CSTC) correlations are proposed to predict heat capacity and thermal conductivity of ILs, respectively. The predicted results agreed well with the experimental data. The proposed FC—CS method and the two corresponding states correlations are important for design, simulation, and analysis of new ionic liquid processes. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1348–1359, 2013     

A simple and efficient method for the preparation of SiO2/PI/AF aerogel composite fabrics and their thermal insulation performance

As a new type of insulation material, aerogels are characterized by a high specific surface area, high porosity, low density and low thermal conductivity, which makes them a new alternative to the use of traditional insulation materials. In this paper, a simple method for preparing aerogel insulation materials is proposed. Specifically, SiO₂/PI/AF (aramid fiber) aerogel composite fabrics were successfully obtained by combining coating technology and finishing processes to use tetraethoxysilane (TEOS) as the precursor, polyimide (PI) powder as the reinforcing agent, and nonwoven AF as the substrate. These composite fabrics were characterized using field-emission scanning electron microscopy (FESEM), tensile testing with an Instron 5967, Fourier transform infrared spectroscopy (FT-IR) and thermal infrared imaging. The results show that the composite fabrics exhibited excellent performance and could effectively block heat transfer. Moreover, the thermal conductivity of the front decreased from 4.08 to 3.91 (W/cm·°C) × 10^-4. This work provides a novel method for the structural design of thermal insulation clothing.     

Towards a methodology for the characterization of fire resistive materials with respect to thermal performance models

A methodology is proposed for the characterization of fire resistive materials with respect to thermal performance models. Typically in these models, materials are characterized by their densities, heat capacities, thermal conductivities, and any enthalpies (of reaction or phase changes). For true performance modelling, these thermophysical properties need to be determined as a function of temperature for a wide temperature range from room temperature to over 1000°C. Here, a combined experimental/theoretical/modelling approach is proposed for providing these critical input parameters. Particularly, the relationship between the three‐dimensional microstructure of the fire resistive materials and their thermal conductivities is highlighted. Published in 2005 by John Wiley & Sons, Ltd.     

基于枚举法的管壳式换热器自动选型软件设计

换热器选型计算需反复试差,过程繁琐,且最终筛选型号单一.以Microsoft Visual Basic 6.0软件为开发平台,结合ACCESS数据库,设计了管壳式换热器自动选型软件.该软件利用了开发平台强大的数据库连接功能,利用枚举法对数据库中所有型号换热器进行验算筛选,并将符合要求设备的运行参数输出至结果列表,给用户提供了较为全面的选择.     

入塔气预热器的结构、焊后热处理及水压试验程序

介绍了鲁奇低压法合成甲醇装置中入塔气预热器的结构、焊后热处理及其水压试验程序,对类似设备的设计、制造具有一定的参考价值。     

SCWO处理轮胎裂解脱硫废液的响应面法优化

采用超临界水氧化(SCWO)法处理废旧轮胎热解过程中产生的脱硫废液,利用响应面法对处理过程中的主要影响因素进行了优化,并通过中心复合设计(CCD)建立了COD去除率的二次回归模型。将实测值与根据模型计算的预测值进行对比,结果表明,以模型代替真实实验点对实验结果进行分析具有较高的可靠性。     

Iterative method to improve calculation of the pre-exponential factor for dynamic thermogravimetric analysis measurements

The conventional isoconversional plot of ln(β/T²) versus 1/T usually has a large error of about −10% in calculation of the pre-exponential factor as a consequence of assuming h(x)=1. Iterative calculation using the plot of ln(β/hT²) versus 1/T is thus suggested. It is illustrated that the iterative method can greatly improve calculation for the pre-exponential factor. Success in calculation for the pre-exponential factor is accompanied by an enhanced accuracy in value of activation energy given by the iterative method in comparison with the conventional isoconversional plot of ln(β/T²) versus 1/T. One explanation is due to the compensation effect of the Arrhenius parameters. The iterative method has been applied to thermal degradation reactions of poly(methyl methacrylate) (PMMA) and polyethylene.     

The use of the simplex method to characterize dry cellulose acetate membranes for gas separations

The normal and log-normal distributions are used to describe the pore size distribution of dry asymmetric cellulose acetate membranes for CO₂/CH₄ separations. Various optimization techniques are implemented to determine the distribution parameters R and σ as well as the constants A₁, and A₂, related to pore structure and surface transport. respectively. By using the Simplex method, a unique solution for the characterization parameters is easily obtained irrespective of the starting search point. The permeation data of helium was used to characterize the membranes and determine the flow parameters which can be used to predict the performance of those membranes in separating CO₂/CH₄ mixtures.     

A reverse-phase high-performance liquid chromatographic method for analyzing complex mixtures of triglycerides. Application to the fat fraction of an aged cheese

Analysis of complex mixtures of triglycerides that span a broad range of partition numbers can entail a number of difficulties. The present study was therefore intended to develop a method of reverse-phase high-performance liquid chromatography using a light scattering detector for analyzing such mixtures. Stationary phase type, mobile phase gradient, column temperature, and injection solvent were the factors used to develop the method. The method improved the selectivity of critical pairs of milk fat triglycerides, providing good resolution for 115 peaks with partition numbers of between 22 and 53. The use of tristearin as internal standard and the relative response factors for different partition number ranges made it possible to more accurately estimate the weight of the sample triglycerides.