Performance Of Thermal Protective Clothing Research Articles

Effects of air gap and compression on the dual performance of multilayer thermal protective clothing under low radiant heat

An air gap in thermal protective clothing (TPC) plays an important role in determining heat transfer, but it may also increase the amount of stored thermal energy that would discharge to the skin after exposure, especially when the TPC suffers compression. To investigate the effect of air gap and compression on the dual thermal protective performance (TPP), thermal hazardous performance (THP) and overall thermal protective performance (OTPP) of TPC, nine air gap configurations with different sizes and positions and five compression levels were designed in this study. Regression models were established to explore the relationships among air gap size, compression and THP for different air gap positions. The results demonstrate that increasing the air gap size without exceeding 12 mm not only significantly enhances the TPP by impeding heat transfer from the heat source to the fabric system during exposure but also decreases the THP by reducing heat discharge from the fabric system to the sensor even when compression is applied. Although an inner air gap contributes more to increasing the TPP during exposure than an outer air gap, it may also bring about severe stored energy discharge when compression is applied. It suggests that a larger air gap size should be divided into individually separate air gaps within different fabric layers to reduce the heat transfer during exposure as well as lower the stored thermal energy discharge after exposure.

Thermal performance of protective clothing (firefighter) under extreme ambient conditions

Protective clothing is made up of multiple layers of textile, which include thermal barrier, moisture barrier, chemical protection and heat radiation protection layers etc. This clothing is commonly used by workers working in the chemical industry, blast furnaces, glass industry, industrial boilers and many more. The ambient conditions for these workplaces are humid and hot in which the clothing is designed for the external protection of heat and fluids but the neglected issue is the internal heat and moisture accumulation. This makes the clothing extremely uncomfortable and significantly reduces the workability of the wearer. The multi-layered structure of this clothing causes the body moisture and heat to trap in between layers, which in extreme ambient conditions like working near the furnace or flash fire causes body burns, these “steam burns” are common and considered to be caused by the condensed moisture trapped in the layers of protective garment. This research aims to firstly investigate the moisture flow through hybrid textile layers and its effect on heat transfer and then secondly to see the impact of extreme radiation flux on the moisture flow inside the textile layers and improvement by using Aerogels.

Studies on the effect of process parameters on the thermal protective performance of multilayer thermal protective clothing

Structural parameters of multilayer thermal protective clothing have a significant influence on thermal protective performance. Variation of pick density in the shell layer, number of layers in the thermal liner, and heat flux is used to study the protection time of thermal protective clothing under high-intensity radiant heat flux. A multi-parametric experimental equation is derived using the Box-Behnken model for accurate predictions and analysis. The test is performed according to ASTM F 1939. The analysis of 3D contours provides us with detailed information on the performance of thermal protective clothing at 1, 2, and 3 layers for various combinations of pick density and heat Flux. The model has a F-value of 309 and a p-value of .0001, indicating that it is statistically significant. The coefficient of correlation between predicted and observed values of protection time is 0.99, which indicates a strong correlation.

Investigation of the dual performance of thermal protective clothing with deformation under low radiant heat exposure

Occupational workers in thermal exposure have frequent physical activities that may lead to fabric deformation of thermal protective clothing. To deeply understand the impact of fabric deformation on its dual thermal protective and thermal hazardous performance, a modified experimental instrument was used to simulate different extents of fabric tensile deformation and compression deformation. The results demonstrated that increasing tensile ratios during exposure decreased heat storage within a fabric system, but increased the skin absorbed energy. Tensile ratios had a more negative impact on the thermal protective performance of a single-layer fabric than of a double-layer fabric system. Increasing tensile ratios during cooling decreased heat discharge to the skin, but the applied compression significantly improved the heat discharge. In addition, regression models were established to examine the effect of fabric deformation and demonstrated that the thermal hazardous performance of fabrics was more affected by compression than by tensile deformation.

Effects of Radiant Heat and Frictional Abrasion on Thermal Protective Performance of Clothing Against High Pressurized Steam

This study focused on changes in protective performance of steam protective clothing after exposure to conditions such as thermal radiation and frictional abrasion. Totally eight radiation conditions varying on exposure duration and times, four types of abrasion scenarios with different friction cycles and three different combined treatments were designed. Results demonstrated that any increase in radiant exposure duration or exposure times would lead to an initial increase and then a following decrease in the steam protective performance. However, the steam protective performance seemed relatively immune to the friction cycles. When thermal radiation and frictional abrasion acted together, interactions between them existed and their specific interaction highly depended on the distribution of heat exposure duration and friction cycles. Findings of this study provided insight into factors influencing steam protective performance, and could be an aid in developing high performance materials or guidelines for use and maintenance of protective clothing.

A prediction method to evaluate thermal performance of protective clothing based on the correlation analysis of the bench scale and flame manikin tests

PurposeBench scale and flame manikin tests are two typical methods to evaluate thermal protective performance (TPP) of fire protective clothing. However, flame manikin test is limited to be widely used for its complication and high cost. The purpose of this paper is to develop a method to evaluate the thermal performance of protective clothing from the bench scale test results and garment parameters, which predicts the body burn injuries without conducting flame manikin tests.Design/methodology/approachBench scale and flame manikin tests’ data were collected from the previous research literature and then statistical analysis was performed to quantitatively investigate the correlations between the two test methods. Equations were established to predict the TPP values accounting for the effects of entrapped air gap and thermal shrinkage. Fitting analysis was conducted to analyze the relationship between the predicted TPP values and total burn injury. Finally, a method to predict total burn injury from the TPP values was proposed and validated.FindingsThe results showed that when the TPP value was predicted with the effects of air gap and thermal shrinkage considered, there was an approximate linear relationship between the predicted TPP values and total burn injury from the manikin test. Therefore, the prediction model of burn injury was developed based on the correlation analysis and verified with a generally good accuracy.Originality/valueThis paper presented a new prediction method to evaluate the thermal performance of protective clothing, which saved significant time and cost compared to the conventional methods. It can provide useful information for burn injury prediction of protective clothing.

Quantitatively evaluating the effects of flash fire exposure on the mechanical performance of thermal protective clothing

PurposeThe purpose of this paper is to determine the effect of flash fire exposure on the mechanical properties of single-layer thermal protective clothing.Design/methodology/approachThe full-scale flame manikin tests were performed to simulate flash fire exposure. Two typical fire-resistant fabrics were investigated. The manikin was divided into seven body parts and the specimens meeting the requirements of tensile and tear strength standards were sampled. Fabric thickness, mass per unit area, tensile strength and tear strength were measured and analyzed.FindingsThe results revealed the significant influence of heat flux on both of tensile and tear strength. However, the regression analysis indicated the low R2 of the liner models. When the tensile and tear strength retention were reorganized based on the body parts, both of the multiple linear regression models for tensile and tear strength showed higher R2 than the one-variable linear regressions. Furthermore, the R2 of the multiple linear regression model for tear strength retention was remarkably higher than that of the tensile strength.Practical implicationsThe findings suggested that greater attention should be paid to the local part of human body and more factors such as the air gap should be considered in the future thermal aging of firefighters’ clothing studies.Originality/valueThe outcomes provided useful information to evaluate the mechanical properties of thermal protective clothing and predict its service life.

Development of a device for 3D surface reconstruction of thermal shrinkage of flame-resistant fabrics

Thermal shrinkage of flame-retardant fabrics under high temperature exposure would result in the change of air layer under clothing, which can affect the thermal protective performance of clothing. This paper introduces a new image-based device to characterize the thermal shrinkage of the fabrics. The device was aimed to reconstruct the three-dimensional (3D) surface morphology of fabrics based on grayscale images. The imaging collecting system was designed to obtain the grayscale images of thermal-shrinkage fabrics. Then, MATLAB programming of the 3D reconstruction algorithm based on photometric stereo was developed. A comparison of the results of the 3D reconstruction method with the 3D scanning method showed that the 3D reconstruction method was practical and repeatable. The research provides a simple and effective method to characterize the 3D morphology of thermal-shrinkage fabrics, which will help in the quantification of thermal shrinkage of fabrics and the prediction of the thermal protective performance of clothing.

A Coupled Model for Heat and Moisture Transport Simulation in Porous Materials Exposed to Thermal Radiation

Understanding mechanism of transmitted and stored heat in porous materials was extremely important for improving thermal protective performance of clothing. A coupled heat and moisture transfer model in a three-layer fabric system while exposing to a low-level thermal radiation was developed in this study. The model simulated the transmitted and stored heat in porous materials, and considered the effect of moisture transport on the transmitted and stored heat. The predicted results from the coupled model were validated with the experimental results, and compared with the predicted results from the previous model without considering the moisture effect. It was found that the prediction accuracies in skin burn and skin temperature through the coupled model were further improved. The coupled model was used to examine the moisture effect on heat transport and storage in porous materials. The results demonstrated that the moisture within porous materials increased the heat storage and discharge, but decreased the heat transport. The increases in initial moisture content and fiber moisture regain, while increasing the thermal hazardous effect, greatly enhanced the thermal protective performance of clothing. Therefore, it suggested that the moisture management in porous materials was a key consideration for thermal functional design of fabric.

Quantification of the energy storage caused dual performance of thermal protective clothing containing with moisture exposed to hot steam

AbstractExcept for providing thermal protection, thermal protective clothing (TPC) may also impose thermal hazards on human skin due to the discharge of energy storage. The dual thermal protective/thermal hazardous performance of TPC is rather complicated when TPC gets wet from internal and external sources and especially when it is exposed to conditions of pressurized hot steam. In this study, several indices were used to quantitatively investigate the influences of moisture location, moisture content within TPC, and their combined effect on the energy storage caused dual performance of TPC under exposure to steam. Results showed that both the increasing of external and internal moisture could decrease heat absorption of the skin and increase burn injury time under steam exposure through heat storage, but the positive effect of the external moisture amount was more obvious. The external moisture amount had no significant effect on heat discharge from TPC to the skin, whereas the internal moisture amount increased heat discharge. Empirical models were successfully established to predict the energy absorption of human skin and the burn injury time. Research outcomes of this study will contribute to thoroughly understanding the impact of moisture on dual performance under steam exposure and provide new insights into the development of functional textile materials.

Effect of Compression on Contact Heat Transfer in Thermal Protective Clothing Under Different Moisture Contents

Contact burns pose a serious threat on firefighters’ health, safety, and job performance. The objective of the study was to analyze the effects of compression and moisture content on thermal protective performance of clothing. Skin-simulant sensor and Pennes bio-heat transfer model were used to predict time to cause skin contact burn. A new index (heat transfer efficiency) was proposed to examine the effects of applied pressure and moisture level on the contact heat transfer in the thermal protective clothing. It was demonstrated that the addition of moisture nonlinearly decreased the thermal protective level of clothing. The fabric thickness was greatly decreased by the compression, but the thermal protective level presented no significant difference between two kinds of pressures. The heat transfer efficiency was an effective index for evaluating the contact heat transfer, which was determined by the basic properties of fabric, the moisture content, and the pressure level. The conclusions from this study could contribute to understanding the effects of compression and moisture on the contact heat transfer, thus providing the principle of thermal protection against skin contact burns.

On the Improvement of Thermal Protection for Temperature-Responsive Protective Clothing Incorporated with Shape Memory Alloy.

This study explored the application of shape memory alloy (SMA) springs in a multilayer protective fabric assembly for intelligent insulation that responded to thermal environment changes. Once the SMA spring was actuated, clothing layers were separated, creating an adjustable air gap between the adjacent fabric layers. The impacts of six different SMA arrangement modes and two different spring sizes on thermal protection against either a radiant heat exposure (12 kW/m2) or a hot surface exposure (400 °C) were investigated. The findings showed that the incorporation of SMA springs into the fabric assembly improved the thermal protection, but the extent to which the springs provided thermal protection was dependent on the arrangement mode and spring size. The effectiveness of reinforcing the protective performance using SMA springs depended on the ability of clothing layers to expand an air layer. The regression models were established to quantitatively assess the relationship between the air gap formed by SMA spring and the thermal protective performance of clothing. This study demonstrated the potential of SMA spring as a suitable material for the development of intelligent garments to provide additional thermal protection and thus reduce the number of clothing layers for transitional thermal protective clothing.

재사용 및 제한적 화학보호복의 열적 성능 평가에 관한 연구

In this study, the thermal performance of limited and reusable thermal chemical protective clothing from domestic and foreign countries were investigated in terms of flame resistance and thermal protective performance. The results showed that the performance of thermal protective clothing certificated by KFI was comparable with that of foreign products certificated by NFPA 1991 and EN 943, respectively. Moreover, the cumulative flame time of all three products were zero second and the burning distance of S sample exhibited two times higher than that of the other two samples. The thermal protective clothing of chemical protective clothing made of nonwoven fabric is better than that of the other ones. There was no burn injury until 6 seconds from flash fire test, but 5.8 % of second burn injuries were observed after 12 seconds. In addition, Inflating the chemical protective clothing would increase the exposure time when encountering the chemical flash fire.

재사용 및 제한적 화학보호복의 열적 성능 평가에 관한 연구

In this study, the thermal performance of limited and reusable thermal chemical protective clothing from domestic and foreign countries were investigated in terms of flame resistance and thermal protective performance. The results showed that the performance of thermal protective clothing certificated by KFI was comparable with that of foreign products certificated by NFPA 1991 and EN 943, respectively. Moreover, the cumulative flame time of all three products were zero second and the burning distance of S sample exhibited two times higher than that of the other two samples. The thermal protective clothing of chemical protective clothing made of nonwoven fabric is better than that of the other ones. There was no burn injury until 6 seconds from flash fire test, but 5.8 % of second burn injuries were observed after 12 seconds. In addition, Inflating the chemical protective clothing would increase the exposure time when encountering the chemical flash fire.

Measurements in flame retardant textiles and protective clothing using an instrumented

The flame test manikin system can be used to evaluate the performance of thermal protective clothing under fire simulation conditions. Different weights of thermal protective garments were tested and the total clothed burn injury area decreased as the fabric weight increased. In addition, a comparison of different compositions for the same weight was analyzed too.

Application of waterproof breathable fabric in thermal protective clothing exposed to hot water and steam

A hot water and steam tester was used to examine thermal protective performance of waterproof and breathable fabric against hot water and steam hazards. Time to cause skin burn and thermal energy absorbed by skin during exposure and cooling phases was employed to characterize the effect of configuration, placing order and properties of waterproof and breathable fabric on the thermal protective performance. The difference of thermal protective performance due to hot water and steam hazards was discussed. The result showed that the configuration of waterproof and breathable fabric presented a significant effect on the thermal protective performance of single- and double-layer fabric system, while the difference between different configurations in steam hazard was greater than that in hot water hazard. The waterproof and breathable fabric as outer layer provided better protection than that as inner layer. Increasing thickness and moisture regain improved the thermal protective performance of fabric system. Additionally, the thermal energy absorbed by skin during the cooling phase was affected by configuration, thickness and moisture regain of fabric. The findings will provide technical data to improve performance of thermal protective clothing in hot water and steam hazards.

Development of correlations and artificial neural network models to predict second-degree burn time for thermal-protective fabrics

Firefighters and operators working near industrial furnaces or ovens usually encounter extreme environmental conditions. Heat transfer through fabrics exposed to such high heat flux exposures causes skin burn. There are various parameters which govern heat transfer and second degree burn time in such situations. In this work, six dimensionless parameters associated with heat transfer through fabrics exposed to various flame and radiant heat flux exposures are obtained. Correlations for dimensionless second degree burn time are obtained in terms of other non-dimensional parameters. These separate correlations for each type of exposure can be used to obtain thermal protective performance (TPP) of any fabric exposed to different type of heat conditions, provided that fabric material, fabric geometric parameters, air gap between fabric and skin, and intensity of heat exposure are known. Artificial neural network (ANN) approach is also used to predict TPP of clothing. Multi-layer feed-forward back-propagation networks are developed for different type of exposures. Results shows that both correlations and ANN approach used in the study are promising. ANN model predictions are found to agree better with experimental observations as compared to the outcome of developed correlations. Importance of various dimensionless parameters obtained using dimensional analysis are also emphasized.

Combined effects of moisture and radiation on thermal performance of protective clothing

Purpose– The purpose of this paper is to study the combined effects of moisture and radiation on thermal protective performance of protective clothing exposed to low level radiation.Design/methodology/approach– Using a sweating manikin, the effect of radiation and moisture on heat and moisture transfer was initially analyzed under the dry manikin with sweating rate of 100 g/(m2h) exposed to 2.5 kW/m2, and then studied at 200 and 300 g/(m2h) exposed to 2 and 3 kW/m2, respectively. Finally, the combined effects of thermal radiation and moisture were predicted by fitting the relationships among heat loss and wet skin surface temperature, with the sweating rate and radiation intensity.Findings– The results show that the heat loss and the wet skin surface temperature are affected by the combined effects of moisture and radiation, with two distinctly different trends. Heat loss from the manikin is increasing with the sweating rate, and decreasing with thermal radiation intensity. However, the wet skin surface temperature has an opposite situation.Originality/value– Two filling equations are given to present the relationships among heat loss and wet skin surface temperature, with the sweating rate and radiation intensity. With these two equations, the heat loss and the wet skin surface temperature when exposed to radiation can be predicted by only measuring the mean radiant and ambient temperatures and controlling the sweating rate.

Determination of the thermal protective performance of clothing during bench-scale fire test and flame engulfment test: Evidence from a new index

The protective performance of heat- and flame-resistant materials can be studied using a bench-scale test or a full-scale instrumented manikin test. However, there are some limitations of these evaluation methods. The existing bench-scale test could not be applied entirely to assess the thermal protective performance of fabrics if the exposure duration is fixed, while the existing manikin test only provides limited information about the local difference in thermal insulation. This study developed a new index of maximum attenuation factor to second-degree burn injury (maximum attenuation factor) as an improved quantitative method of the thermal protective performance, and then investigated the use of maximum attenuation factor during the bench-scale test as well as the manikin test. It demonstrated that the calculations of maximum attenuation factor were highly repeatable. In both the bench-scale and the manikin test, strong correlations were found between the results derived from the proposed method and the measurements from the existing test method. The results between the bench-scale test and the manikin test can also be compared as a united index.

The impact of air gap on thermal performance of protective clothing against hot water spray

The air gap size and distribution developed between clothing and a human body play a critical role in clothing performance, specifically for thermal protective clothing. Hot liquid is considered as one of the common hazards in industrial working environments. In this study, the clothing air layer entrapped between protective clothing and a manikin body was determined using three-dimensional body scanning, and the protective performance provide by the clothing was predicted using an instrumented hot water spray manikin evaluation system. The relationship between the average air gap size and overall protective performance was analyzed. The impact of clothing air gap developed along the human body on predicted burn injury was considered. In addition, the air gap distribution and its relation to skin burn injury were compared for the selected garments. In general, the results indicated that the average air gap size showed positive effects on the overall protective performance. For all body parts except the pelvis, the air gap size presented a significant relationship with the percentage of burn injury. For an individual garment, there was no significant correlation found between the air gap distribution and skin burn injury. The garment with a larger air gap size and minimal air gap changes during hot water spray provided better protective performance. The research findings could provide the technical basis for further development of high performance protective clothing.