Hot steam transfer through heat protective clothing layers.

The aim of this study was to analyse the transfer of steam through different types of textile layers as a function of sample parameters such as thickness and permeability. In order to simulate the human body, a cylinder releasing defined amounts of moisture was also used. The influence of sweating on heat and mass transfer was assessed. The results show that in general impermeable materials offer better protection against hot steam than semi-permeable ones. The transfer of steam depended on the water vapour permeability of the samples, but also on their thermal insulation and their thickness. Increasing the thickness of the samples with a spacer gave a larger increase in protection with the impermeable samples compared to semi-permeable materials. Measurements with pre-wetted samples showed a reduction in steam protection in any case. On the other hand, the measurements with a sweating cylinder showed a beneficial effect of sweating.     

Dry and wet heat transfer through clothing dependent on the clothing properties under cold conditions.

The purpose of this study was to investigate the effect of moisture on the heat transfer through clothing in relation to the water vapour resistance, type of underwear, location of the moisture and climate. This forms part of the work performed for work package 2 of the European Union THERMPROTECT project. Thermal manikin results of dry and wet heat loss are presented from different laboratories for a range of 2-layer clothing with similar dry insulations but different water vapour permeabilities and absorptive properties. The results obtained from the different manikins are generally consistent with each other. For each climate, total wet heat loss is predominately dependent on the permeability of the outer layer. At 10 degrees C, the apparent evaporative heat loss is markedly higher than expected from evaporation alone (measured at 34 degrees C), which is attributed to condensation within the clothing and to increased conductivity of the wet clothing layers.     

Assessing gait changes in firefighters due to fatigue and protective clothing

Each year, roughly 11,000 firefighters are injured as a result of slips, trips and falls, which account for over 25% of all fireground injuries. Wearing personal protective equipment (PPE) can increase risk of fall-related injuries due to its weight, restrictiveness, and increased heat stress. Modification of PPE may serve to mitigate firefighter injuries related to loss of balance and falls. We examined the effects of choosing ‘enhanced’ protective clothing (lightweight, breathable, and less restrictive compared to typical firefighting PPE) and simulated firefighting tasks (18-min bout over four activities) on subsequent gait performance. To assess the effect of wearing protective clothing and firefighting activity, seven gait parameters and three movement errors were assessed during level and obstacle-crossing walking tasks. Forty-four firefighters wore one of two types of PPE (‘Standard’, ‘Enhanced’) during three testing conditions (baseline in station uniform, pre-firefighting activity in PPE, and post-firefighting activity in PPE). The effect of donning any PPE was found to significantly impair gait performance. Fatigue may impact effective mobility since more movement errors were observed during post-activity than pre-activity assessments. Although the Enhanced PPE did not lead to any significant differences in gait parameters compared to Standard PPE, participants in Enhanced PPE made twice as many movement errors, potentially attributed to lack of familiarity with the gear. These results suggest that wearing firefighting PPE and heat-stress induced fatigue are associated with reduced gait performance and increased risk for tripping over obstacles.     

Performance of firefighters' protective clothing after heat exposure.

Heat and mechanical protection properties of 6 fabric combinations commonly used in firefighters' protective clothing were assessed before and after different heat treatment. It was shown that after heat exposure, the values obtained were generally lower than in the original state. The mechanical properties of the materials were more affected by heat than by heat protective properties. In 2 cases, degradation started before a visible change in the material could be observed, which might be potentially dangerous for the end user who will not realize the alteration of the material.     

Selection of sorption material for tests of pesticide permeation through protective clothing fabrics.

The paper presents the results of studies on selecting a solid sorption material for absorbing liquid crop protection agents which permeate samples of protective clothing fabrics. The sorption materials were investigated and selected with an assumption that they should have a high recovery coefficient for biologically active substances, used as active ingredients in crop protection agents, at a presumed, acceptably high level. The selected substances were determined with a gas chromatograph equipped with an electron capture detector (dichlorvos, cypermethrin and 2,4-D) and a nitrogen-phosphorus detector (carbofuran). The tests demonstrated that polypropylene melt-blown type unwoven cloth had high recovery coefficients for all 4 active ingredients proposed for the study. The highest recovery coefficient, -.97, was obtained for carbofuran. The recovery coefficients obtained for the 3 remaining substances were lower: .89 for cypermethrin and 2,4-D, and .84 for dichlorvos.     

Optimizing the performance of phase-change materials in personal protective clothing systems.

Phase-change materials (PCM) can be used to reduce thermal stress and improve thermal comfort for workers wearing protective clothing. The aim of this study was to investigate the effect of PCM in protective clothing used in simulated work situations. We hypothesized that it would be possible to optimize cooling performance with a design that focuses on careful positioning of PCM, minimizing total insulation and facilitating moisture transport. Thermal stress and thermal comfort were estimated through measurement of body heat production, body temperatures, sweat production, relative humidity in clothing and subjective ratings of thermal comfort, thermal sensitivity and perception of wetness. Experiments were carried out using 2 types of PCM, the crystalline dehydrate of sodium sulphate and microcapsules in fabrics. The results of 1 field and 2 laboratory experimental series were conclusive in that reduced thermal stress and improved thermal comfort were related to the amount and distribution of PCM, reduced sweat production and adequate transport of moisture.     

Refinery firefighters: assessing fitness for duty.

Firefighting is a hazardous and physically demanding activity. The demanding nature of the tasks involved in firefighting requires a high level of fitness both for the safety of the firefighting personnel as well as for the adequate performance of their tasks. Here, the characteristics (body weight, lung function, etc.) of a small group of refinery firefighters were investigated using exploratory factor analysis and discriminant analysis. The results indicated that there is a group of factors that characterize those individuals meeting minimum fitness requirements as described previously in the literature. The factors that were identified included those related to anthropometry (such as body composition and weight) and those related to physical capabilities (such as push-ups). Since these data are collected relatively easily in most occupational settings, they may offer an efficient surrogate method to determine fitness for duty among firefighters.     

Effectiveness of a light-weight ice-vest for body cooling while wearing fire fighter's protective clothing in the heat.

The aim of the study was to examine the effects of wearing an ice-vest (ca 1 kg) on physiological and subjective responses in fire fighters. The experiments were carried out on a treadmill in a hot-dry environment. The physical cooling effect of the ice-vest was measured with a thermal manikin. The ice-vest effectively reduced skin temperatures under the vest. On average, heart rate was 10 beats/min lower, the amount of sweating was reduced by 13%, and subjective sensations of effort and warmth were lower during work with the ice-vest compared to work without it. Thermal manikin tests indicated that the useful energy available from the vest for body cooling was rather high (58%). In conclusion, the ice-vest reduces physiological and subjective strain responses during heavy work in the heat, and may promote efficient work time by 10%.     

Numerical simulations of heat and moisture transport in thermal protective clothing under flash fire conditions.

A numerical model of heat and moisture transport in thermal protective clothing during exposure to a flash fire was introduced. The model was developed with the assumption that textiles are treated as porous media. The numerical model predictions were compared with experimental data from different fabric systems and configurations. Additionally, with the introduction of a skin model, the parameters that affect the performance of thermal protective clothing were investigated.     

Age-related thermal strain in men while wearing radiation protective clothing during short-term exercise in the heat.

The aim of the study was to compare heat strain among different age groups of men in protective clothing during short-term physical work. Eight young (20-29 years), 6 middle-aged (41-55 years), and 6 older (58-65 years) men exercised for 30 min on a cycle ergometer (40% V(O2 max)) in 2 hot environments with a similar WBGT (ca. 26 degrees C): once with minimal clothing without infrared radiation (E1), and once with aluminized protective clothing under infrared radiation (E2). All subjects had sedentary jobs, but only the older subjects were physically active in their leisure-time. Body temperatures, heart rate, sweat rate, and subjective feelings were determined during the tests. Higher thermal strain was observed in E2 than in E1. No age-related differences in thermal strain were observed in either experiment indicating that active older men can tolerate short work periods with protective clothing in the heat as well as younger sedentary men.     

Calculation of clothing insulation by serial and parallel methods: effects on clothing choice by IREQ and thermal responses in the cold.

Cold protective clothing was studied in 2 European Union projects. The objectives were (a) to examine different insulation calculation methods as measured on a manikin (serial or parallel), for the prediction of cold stress (IREQ); (b) to consider the effects of cold protective clothing on metabolic rate; (c) to evaluate the movement and wind correction of clothing insulation values. Tests were carried out on 8 subjects. The results showed the possibility of incorporating the effect of increases in metabolic rate values due to thick cold protective clothing into the IREQ model. Using the higher thermal insulation value from the serial method in the IREQ prediction, would lead to unacceptable cooling of the users. Thus, only the parallel insulation calculation method in EN 342:2004 should be used. The wind and motion correction equation (No. 2) gave realistic values for total resultant insulation; dynamic testing according to EN 342:2004 may be omitted.     

Predictive correlations for leaking heat transfer fluid aerosols in air

Mist or aerosol explosions present a serious hazard to process industries. Heat transfer fluids are widely used in the chemical process industry, are flammable above their flash points, and can cause aerosol explosions. Though the possibility of aerosol explosions has been widely documented, knowledge about their explosive potential is limited. Studying the formation of such aerosols by emulating leaks in process equipment will help define a source term for aerosol dispersions and aid in characterizing their explosion hazards.Current research conducted at the Mary Kay O’Connor Process Safety Center involves the non-intrusive measurement of heat transfer fluid aerosol sprays using a Malvern Diffraction Particle Analyzer. A predictive correlation relating aerosol droplet diameters to bulk liquid pressures, temperatures, thermal and fluid properties, leak sizes, and ambient conditions is presented. This correlation can be used to predict the conditions under which leaks will result in the formation of aerosols and ultimately help in estimating the explosion hazards of heat transfer fluid aerosols. The goal is to provide information that will help improve safety in process industries.     

国外热防护服装性能测试技术标准研究

热防护服是热环境下人体安全防护的主要装备,其标准的科学性和系统性对热环境下的人体安全防护具有重要的支持作用.国外对热防护服相关的技术标准予以充分重视,以性能测试技术方法为主体,建立了较为科学、完善的标准,并体现出新的发展趋势.通过对国外热防护服技术标准的调研,总结性能测试标准的共性内容,包括主要性能测试方法、实验设备、实验步骤、烧伤评估、人体模型和测试报告等.整套防护服装的性能测试技术及标准是研究的重点,出汗暖体假人将在防护服装性能测试领域被更为广泛的应用.最后,提出我国研制热防护服性能测试技术标准的建议.     

松散煤体渗流传热试验装置研制

为研究松散煤体低温氧化及通风供氧下的渗流传热规律,研发了渗流传热试验装置。试验装置由气体加湿系统、气体加热系统、煤样反应系统、数据采集系统和安全保护系统组成;本装置可实现自动加湿、控温、自动采集数据及处理数据。为解决装置使用和运行中的安全问题,设计了断电保护、有害气体检测等措施,保障试验装置的安全、可靠。     

Radiation heat transfer in transient dust cloud flame propagation

This study investigates the impact of radiation heat transfer and heat conduction on dust cloud combustion. Radiation plays a very important role in the stability of dust cloud flame, and increasing the amount of radiation drastically raises the possibility of instability and explosion in a dust cloud mixture. Flame speed, which is a function of mixture characteristics, can exhibit a fluctuating behavior. By using the discrete heat source method, it would be possible to study the transient propagation of dust flames. Thus, the propagation speed of flame can be obtained, and as time goes by, the transient speed of dust flame will reach its steady state value. By considering the radiation effect, better agreement is observed between the obtained results and experimental data.     

The influence of sweating on the heat transmission properties of cold protective clothing studied with a sweating thermal manikin.

One of the objectives of the European SUBZERO project was to study the influence of sweat evaporation and condensation on the heat transmission properties of cold protective clothing. With the sweating thermal manikin Coppelius, water vapour transfer through and water condensation in the clothing can be determined simultaneously with the thermal insulation. In this study, 4 cold protective ensembles, intended for use temperatures between 0 and -50 degrees C, were measured with the dry manikin and at 2 different sweating rates. In addition, the ensembles were measured with non-sweating thermal manikins and in wear trials.     

Thermal performance assessment of heat resistant fabrics based on a new thermal wave model of skin heat transfer.

A thermal wave skin model incorporating surface heat flux from a skin simulant sensor is developed to characterize the thermal performance of heat resistant fabrics covering the skin simulant sensor. Comparisons of time to 2nd-degree skin burn and temperature elevation of skin beneath a layer of fabric between the Pennes' equation and the newly developed thermal wave skin model are performed in this research. Results of tolerance time from the Stoll criterion method are also compared with those from 2 skin models in a thermal protective performance calorimeter. It is concluded that the thermal properties of heat resistant fabrics can be characterized more precisely than previously.     

Developing a CFD heat transfer model for applying high expansion foam in an LNG spill

Liquefied natural gas (LNG) is widely used to cost-effectively store and transport natural gas. However, a spill of LNG can create a vapor cloud, which can potentially cause fire and explosion. High expansion (HEX) foam is recommended by the NFPA 11 to mitigate the vapor hazard and control LNG pool fire. In this study, the parameters that affect HEX foam performance were examined using lab-scale testing of foam temperature profile and computational fluid dynamics (CFD) modeling of heat transfer in vapor channels. A heat transfer model using ANSYS Fluent® was developed to estimate the minimum HEX foam height that allows the vapors from LNG spillage to disperse rapidly. We also performed a sensitivity analysis on the effect of the vaporization rate, the diameter of the vapor channel, and the heat transfer coefficient on the required minimum height of the HEX foam. It can be observed that at least 1.2 m of HEX foam in height are needed to achieve risk mitigation in a typical situation. The simulation results can be used not only for understanding the heat transfer mechanisms when applying HEX foam but also for suggesting to the LNG facility operator how much HEX foam they need for effective risk mitigation under different conditions.     

Evaluation of guardrail systems for preventing falls through roof and floor holes

Introduction

Fall-related occupational injuries and fatalities are serious problems in the U.S. construction industry, especially incidents related to unguarded holes. The National Institute for Occupational Safety and Health, Division of Safety Research, Morgantown, WV conducted a project to evaluate the effectiveness of guardrail systems to prevent falls through roof and floor holes.

Methods

Two commercial edge-protection products were evaluated when used as perimeter guarding around a roof hole. Installations of the commercial products were compared to job-built guardrails constructed of 2^″ × 4^″ construction-grade lumber. Occupational Safety and Health Administration (OSHA) regulations require that “a force of at least 200 pounds” must be supported by the top rail of a guardrail system “in any outward or downward direction at any point along the top edge.” A laboratory testing system was developed to evaluate this requirement. A dynamic 200-lb force was generated against the top rail using a weighted manikin mounted on a hinged steel frame. Nine construction workers, who served as test subjects, each built five different guardrail configurations.

Results

All 45 configurations met the 200-lb OSHA requirement. Installation time for one commercial product was 32% quicker than the job-built configuration (25.6 min vs. 37.9 min).

Impact on Industry

This study: (a) indicates that the two edge-protection products can be used as perimeter guarding; (b) highlights the importance of using proper materials and fasteners to construct guardrails to protect workers from falling into unguarded roof and floor holes; and (c) discusses an overall-strength-testing methodology that can be used by fall-protection researchers.     

局部通风掘进巷道风筒综合换热系数确定方法研究

在矿井风流与围岩热湿交换理论的基础上,对局部通风掘进巷道内风流与风筒内风流的热量交换过程进行了研究,提出了通过现场测定巷道内的风流温度、湿度、大气压力、风量和风筒内风流温度等参数来计算风筒综合换热系数的方法.并在平顶山煤矿现场进行了实测,通过对实测计算结果的回归分析,得出了确定风筒综合换热系数的计算公式.研究表明,通过计算巷道内平均风速可以获得风筒综合换热系数.