Protective clothing: Evaluation of zirpro wool and other fabrics

Protective clothing against head and flames should be evaluated not only for flame retardance but also for protection against various heat exposure from convection (flames), conduction (molten metal splashes) and radiation sources, depending on the end use, to ensure a realistic assessment of the potential protection offered and required. Evaluations of various flame-retardant fabrics to different heat exposures showed that the fibre and the flame retardant finish should preferably form a well developed char on exposure to heat, without softening and melting. The flame retardant should act in the solid phase and the fibre should be of low thermal conductivity. For protection against convective heat (flames), a woven Zirpro wool fabric of high density over a bulky knitted Zirpro wool underwear fabric offered a significantly better protection than a single layer of a woven or knitted fabric or a double layer of a woven fabric of the same total weight. The optional multi-layer fabric approach could also decrease overall garment weight and improve wearers' comfort without adverse effect on the protection offered. Of the FR fabrics evaluated, Zirpro wool fabric assemblies showed the longest time to reach pain (first degree burn) and blister (second degree burn) thresholds, as well as the longest pain alarm time–the time available to the wearer to withdraw from the flame heat source before serious injuries occur. Zirpro wool fabric assemblies had one of the lowest residual heat transfers after al limited flame exposure to the pain threshold while some other fibres, e.g. aramid and novoloid, transferred significant residual heat, possibly causing second degree burns. For protection against conduction, such as from molten aluminium splashes, the fabric should have a smooth surface, high density and thickness, besides the other previously mentioned, basic requirements. Zirpro wool fabrics offered a significantly better protection in this case than aramid, FR cotton, glass fibre, asbestos, and other FR fibres. Aluminized fabrics are essential for adequate protection against radiant heat and the aluminization technique affects heat transfer significantly. A low density base fabric made from a fibre of low thermal conductivity, such as Zirpro wool, reduces heat transfer in this case.     

Investigation of air gaps entrapped in protective clothing systems

Air gaps entrapped in protective clothing are known as one of the major factors affecting heat transfer through multiple layers of flexible clothing fabrics. The identification and quantification of the air gaps are two aspects of a multidisciplinary research effort directed toward improving the flame/thermal protective performance of the clothing. Today's three‐dimensional (3‐D) whole body digitizers, which provide accurate representations of the surface of the human body, can be a novel means for visualizing and quantifying the air gaps between the wearer and his clothing. In this paper we discuss how images from a 3‐D whole body digitizer are used to determine local and global distributions of air gaps and the quantification of air gap sizes in single and multilayer clothing systems dressed on a thermal manikin. Examples are given that show concordance between air gap distributions and burn patterns obtained from full‐scale manikin fire tests. We finish with a discussion of the application of air gap information to bench‐scale testing to improve the protective performance of current flame/thermal protective clothing. Copyright © 2002 John Wiley & Sons, Ltd.     

Thermal shrinkage of fabrics used for out layer of firefighter protective clothing under flash fire

The thermal shrinkage of the firefighter protective clothing can greatly affect its thermal protective performance. In this study, a novel and systematic approach to measure the thermal shrinkage of fabrics used for the firefighter protective clothing is presented. The study was limited to fabrics that are used for the outer layer of fire fighter clothing. A total of six different fabrics were tested. They were exposed to a short duration simulation of a structural fire using a Thermal Protection Performance tester. The exposed fabrics were then scanned with a hand‐held laser scanner for their 3D surface appearance. Software named Geomagic Studio was used to deal with the point clouds of the fabric images. Another software package named ArcGis, which was normally used in geological studies, was then used to analyze the heights and slope angles of the tags and crests of the burned fabrics. The results showed that for the fabrics tested the thicker and heavier the fabric, the smaller was the thermal shrinkage. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of external heat flux and coating thickness on the thermal insulation properties of two different intumescent coatings using cone calorimeter and numerical analysis

Polymeric intumescent coatings are fire protective materials that increase their thermal resistance when exposed to high temperatures to prevent building structures from damage. The idea of the investigation was to develop a simple test method to determine the time dependent thermal conductivity of intumescent coatings. Therefore steel plates were coated with two different intumescent systems. During cone calorimeter tests the temperature at the back side of the coated plates was measured. These results were used to calculate the time dependent thermal resistance of the protective layer with the simulation program IOPT2D for different external heat fluxes and different layer thickness. Copyright © 2003 John Wiley & Sons, Ltd.     

Quantitative investigation of air gaps entrapped in multilayer thermal protective clothing in low‐level radiation at the moisture condition

The effects of air gaps entrapped within the multilayer protective clothing system on the thermal performance were studied during low‐level radiation (2–10 kW/m²). A bench‐scale apparatus was designed to produce the liquid droplets and simulate human sweat transferring through the multilayer fabric system. Two air gaps located between the outer shell and the moisture barrier (Gap A) and between the moisture barrier and the thermal liner (Gap B) were used with different gap sizes (0, 2, and 5 mm). The thermal resistance analysis for the heat transfer with a multilayer flat wall was used to interpret the effects of air gap. The results show that the total thermal resistance of a multilayer clothing system and the thermal resistances of the two air gaps are linearly related with the level of heat flux. It is also indicated that the air gap position affects the beneficial effect of the gap size. The effect of Gap B to improve the thermal performance is better than that of Gap A. Copyright © 2014 John Wiley & Sons, Ltd.     

3D heat transfer modeling and parametric study of a human body wearing thermal protective clothing exposed to flash fire

Understanding the heat transfer mechanism through a clothed man system in extreme environments is of great significance for human thermal protection. Three‐dimensional heat transfer models were developed based on the computational fluid dynamics considering a real‐shape human body in this study. The influences of air gap width, clothing thickness, and emissivity on the heat transfer within a dressed manikin exposed to flash fire were investigated. Simulated results indicated that the heat transfer in the air space was more complicated on the garment level than the fabric, because of the varying relative positions between different body segments and the heat source, as well as the ventilation openings. Increasing the fabric thickness was an effective method to reduce the transferred energy, which could remarkably lower the skin temperature. Decreasing both of the surface and backside emissivity from 0.9 to 0.3 could increase the protective performance, where surface emissivity reduction was recommended since the decrease of clothing temperature could minimize the risks of fabric degradation. The purpose of assuming the uniform air gap was to perform the parametric study, which was unrealistic indeed. The model with real clothing shape will be developed and investigated in the near future.     

Manikin test for flame engulfment evaluation of protective clothing: Historical review and development of a new ISO standard

The overall performance of a firefighter turnout suit can only be evaluated using both bench‐scale tests and an assessment based on an instrumented manikin under defined, close to real‐life conditions in a laboratory. Using manikins in rating protective clothing has already a long history which will be reflected in this paper. Efforts all over the world to reproduce a flame engulfment situation in a laboratory are currently being combined in a new draft international standard (ISO/DIS 13506.3). A round robin test showed an acceptable reproducibility for this method based on a manikin test and a gas burner system. An overview of existing measurement systems and the results of this round robin are discussed and possible improvements for the standard flame engulfment test method are proposed. Copyright © 2006 John Wiley & Sons, Ltd.     

PVDF中空纤维换热管超疏水表面强化蒸气滴状冷凝传热

为了提高塑料换热管的传热性能，通过两步涂覆法制备了具有超疏水表面的复合塑料换热管。首先采用多孔PVDF中空纤维膜为支撑层，以导热材料纳米ZnO填充聚二甲基硅氧烷（PDMS）为皮层，制备了具有致密外表皮层的复合塑料换热管。其次为了强化蒸气的滴状冷凝传热，通过考察正硅酸乙酯含量，氨水含量等条件的影响，制备出了具有超疏水表面的PVDF复合塑料换热管。结果表明，所制备的换热管表面接触角可达154°，与熔融法及NIPS法制备的换热管相比，总传热系数可提高85.3%～147.3%。     

Flame retardation of dibromoneopentyl glycol on intumescent flame‐retardant/low‐density polyethylene composites

On the basis of ammonium polyphosphate (APP) microencapsulated with pentaerythritol/dibromoneopentyl glycol (DBNPG) mixed phosphate melamine salt as an intumescent flame retardant (IFR), the influence of DBNPG on the flame retardancy of IFR/low‐density polyethylene was investigated. The results prove that DBNPG could influence the combustion heat and the thermal barrier properties of the char layer in combustion. The intumescent degree (ID), compactness, and closure were the determinants of the thermal barrier properties of the char layer. A greater ID below 500°C and then a more compact and closed char layer above 500°C contributed to the better thermal barrier properties. An appropriate DBNPG reduced the combustion heat and promoted the formation of a compact and closed char layer by increasing of the melting viscosity of the composites. However, excessive DBNPG destroyed the closure of the char layer and increased the combustion heat because of a decrease in the melting viscosity of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41244.     

基于火积耗散热阻的内置双旋线换热管性能研究

基于换热器火积耗散热阻理论,采用三维数值模拟计算方法,以水为流动介质,分别对内置双旋线外径为9mm、12mm、15mm、18mm的换热管的管内流场和火积耗散热阻进行研究,分析了内置双旋线换热管的传热和流动特性,结果表明：内置双旋线换热管内流体呈现三维螺旋状流动,管壁面附近周向和径向速度明显增强,从而中心区域流体和壁面附近流体充分混合;内置双旋线换热管的换热量与其积耗散热阻相对应,积耗散热阻越小,换热量越大;内置双旋线换热管的积耗散热阻随着雷诺数的增大而减小;内置双旋线换热管的协同性均优于光管,说明内置双旋线换热管具有良好的综合换热性能.     

Zirpro wool textiles

The overall flammability hazard of Zirpro wool protective clothing, carpets and upholstery with regard to national and international standards is summarized. Protective clothing against heat and flames has to be evaluated not only for flame-retardance by a vertical flame test but also for heat transfer from convective (flames), radiant and conductive (molten metal) heat exposure to ensure a realistic assessment of the potential protective offered and required. Textile furnishings (carpets, upholstery, curtains) have to be evaluated for flame-retardance, heat release, smoke emission and toxicity of combustion products to assess the overall flammability hazard. Evaluation and consideration of only on e flammability parameter, e.g. toxicity of combustion products, can lead to misleading conclusions about the flammability hazard of a material.     

防弹衣用新型充气防护散热片制备及性能

介绍了一种防弹衣用新型充气防护散热片,从外观设计、防护散热片面料选择、云母冰凉纤维的制备原理等方面简述了充气防护结构的设计方法,并对该散热片结构进行了红外热成像验证和实际穿戴效果验证。研究结果表明,该结构作为防弹衣缓冲层有利于改善防弹衣载体人体工学负载均匀分布、减轻疲劳、增加耐力,提高穿着舒适度,并能够持续性为防弹衣散热,同时该散热片可以增大人体和防弹衣的接触距离,降低了防弹衣受到弹击时对人体的损伤程度,提高了穿着安全性。     

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.     

Ablation behavior of Cf/ZrC-SiC-based composites fabricated by an improved reactive melt infiltration

In this work, a highly dense C_f/ZrC-SiC-based composite is fabricated by an improved reactive melt infiltration (RMI). The ablation resistance of the composite is studied by air plasma test. The RMI-C_f/ZrC-SiC possesses a low porosity (3.49%) and high thermal conductivity. The dense microstructure can effectively retard oxygen from diffusing into the interior composite. Meanwhile, the high thermal conductivity makes the composite transfer heat timely during ablation, which reduces the heat accumulation on the ablation surface and weakens the thermal damage to the composite. Consequently, the as-fabricated composite exhibits an excellent ablation resistance. Compared to conventional PIP-C_f/ZrC-SiC composite, the linear and mass recession rates of the RMI-C_f/ZrC-SiC decline by 98.07% and 39.02% at a heat flux of 4.02 MW/m². Also, a continuous SiO₂-ZrO₂ layer forms on the sample surface, which isolates the sample surface from the plasma flame and protect the composites from further oxidation and ablation.     

Heat and mass transfer and stabilization of combustion in the boundary layer behind a rib and a backward-facing step

A comparison of the characteristics of the boundary layer with combustion with flame stabilization by a rib and a backward-facing step is performed. Data on the thermal boundary layer, the flame blow-off velocity, and the rate of ethanol evaporation into an air flow with a turbulence intensity of up to 26% are obtained. It is shown that the temperature of the outer region of the boundary layer and the flame blow-off velocity behind the rib are higher than those behind the backward-facing step. With both methods of flame stabilization, the intensity of evaporation corresponds to transient mass transfer.     

甲纶消防员灭火防护服热防护性能研究

采用符合XF 10—2014《消防员灭火防护服》标准的甲纶四层面料与芳纶四层面料,测试其组合的热防护系数(TPP值);用同样的面料制作灭火防护服,并通过假人燃烧实验对比甲纶灭火防护服与芳纶灭火防护服的整体热防护性能.结果表明:甲纶防护服热防护系数不及芳纶灭火防护服,但整体热防护性能远超现行芳纶灭火防护服,甲纶灭火防护服...     

滚塑成型工艺加热阶段的数值研究

为一个球形中空塑料制品的滚塑成型工艺的加热阶段建立了一种新的流动与传热理论模型,并采用Fluent软件对其进行数值计算。该理论模型将模具的导热、塑料层的导热和随后的熔融以及内部空气的自然对流换热耦合起来求解。数值计算所得的加热时间、模具外壁面温度和内部空气温度都与实验结果吻合较好,从而证明了本理论模型的有效性。最后采用该理论模型分别计算了在不同外部加热温度、外部对流换热系数以及塑料粉末层厚度下的加热时间,从而确定了这些参数对加热时间的影响,并得出了提高外部对流换热系数比提高外部加热温度能更有效地缩短加热时间等结论。     

水平管油气两相段塞流及其传热特性

海底油气管道的冷却传热过程是结蜡、水合物等海洋石油工业流动保障问题的关键控制因素。采用电容探针与热电偶、热电阻等流动及温度测量手段对不同冷却条件下空气-油段塞流的流动参数和传热参数进行实验测量,分析了空气-油段塞流流动参数对传热特性的影响,并与空气-水对流换热进行对比。结果表明,空气-油段塞流对流传热系数主要受液相折算速度的影响,且冷却液温度越低,管底热流体黏度越大,导致热边界层越厚,传热系数降低;受黏性力及边界层影响,对流传热系数远小于空气-水;沿管壁周向,从管顶到管底的对流传热系数不断增大。提出了适用于冷却条件下的油气段塞流传热关联式和传热模型。     

Quantitatively assessing the effect of exposure time and cooling time of fabric assemblies representative of those used in firefighter clothing on the thermal protection

In addition to direct thermal energy from a heat source, a large amount of thermal energy stored in clothing will continuously transfer to skin during the cooling of fabric assemblies. In real situations, the durations of thermal exposure and cooling in protective clothing vary. Eight exposure times ranging from 6 to 27 s and a maximum duration of 80 s cooling time were used. To quantitatively investigate the levels of thermal protection, a new index was applied. The effects of exposure and cooling times on the grade of thermal protection were discussed. The effective cooling time was found to be 9–40 s for the selected fabric systems. In addition, a safety time region was identified and proposed as an indicator to evaluate the thermal protective insulation of fabric assemblies. The data analyses clearly showed that in addition to the inherent properties of the fabric materials, the levels of protection were not only related to exposure time but also depended upon the cooling time. Copyright © 2015 John Wiley & Sons, Ltd.