Analyzing steam transfer though various flame-retardant fabric assemblies in radiant heat exposure

2016 ◽  
Vol 47 (5) ◽  
pp. 853-869 ◽  
Author(s):  
Yun Su ◽  
Jun Li
Keyword(s):  
Thermal Radiation ◽  
Thermal Energy ◽  
Thermal Protection ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Positive Influence ◽  
Air Permeability ◽  
Fabric System ◽  
Layered Fabric ◽  
Nonfatal Injuries

Protection from steam burns is beneficial to reduce the nonfatal injuries of firefighters in firefighting and rescue operations. A new multifunctional testing apparatus was employed to study heat and steam transfer in protective clothing under low-pressure steam and low-level thermal radiation. Single-, double-, and triple-layered fabric assemblies were selected in this experiment. It is indicated that the existence of hot steam weakens the positive influence of the fabric’s thickness, but increases the importance of the air permeability on the thermal protection. The fabric assemblies entrapping moisture barrier can better resist the penetration of steam through the fabric system, and significantly improve the thermal protection in low steam and thermal radiation exposure due to the low air permeability. Additionally, the total transmitted energy ( Qe) and dry thermal energy ( Qd) under low steam and thermal radiation are dramatically larger than that under thermal radiation ( p < 0.05), while hot steam insignificantly reduces the thermal energy during the cooling ( p = 0.143 > 0.05). The understanding of steam heat transfer helps to provide proper guidance to improve the thermal protection of the firefighter’s clothing and reduce steam burns.

Quantitative assessment of the thermal stored energy in protective clothing under low-level radiant heat exposure

2017 ◽  
Vol 88 (24) ◽  
pp. 2867-2879 ◽  
Author(s):  
He Jiazhen ◽  
Chen Yan ◽  
Wang Lichuan ◽  
Li Jun
Keyword(s):  
Energy Storage ◽  
Thermal Resistance ◽  
Thermal Energy ◽  
Protective Clothing ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Air Gap ◽  
Heat Fluxes ◽  
Total Thermal Resistance ◽  
Fabric System

In addition to direct thermal energy from a heating source, a large amount of thermal energy stored in clothing will continuously discharge to the skin after exposure. Therefore, thermal protective clothing may have a dual effect on human skin in reality. An experimental investigation was conducted to study the energy storage within 15 different combinations of clothing layers exposed to low heat fluxes ranging from 2.5 kW/m2 to 8.5 kW/m2. The energy storage process, the distribution of energy storage, and variables critically impacting energy storage, including fabric layers, air gap under clothing, thermal resistance and heat source intensity were discussed. It is demonstrated that the weight and thickness of the fabric are dominating factors affecting energy storage. For a multilayer fabric system, 36–57% of the total amount of energy is stored in the outer shell. The neighboring layer proves to be very important for the energy storage in an individual fabric. The air gap that exists between the fabric and the skin exerts an influence on the energy storage within fabric layers. In addition, a linear correlation is observed between the energy storage and the total thermal resistance of a fabric system. The research findings will be brought to researchers to better understand the mechanism and factors associated with energy storage and help develop new fabric combinations in order to minimize heat transmission to the skin.

scholarly journals APPLICATION OF ABLATION MATERIALSFOR HEAT PROTECTION OF CABINS OF FIRE-FIGHTING MACHINES

2020 ◽  
Vol 9 (4) ◽  
pp. 134-141
Author(s):  
Vladimir Kotenko ◽  
Vladimir Abrazumov ◽  
Mihail Ermochenkov
Keyword(s):  
Thermal Radiation ◽  
Forest Fire ◽  
Forest Fires ◽  
Thermal Protection ◽  
Protective Coatings ◽  
Heat Exposure ◽  
Heat Fluxes ◽  
Main Requirement ◽  
Low Efficiency ◽  
Intense Heat

Forest fires are accompanied by the release of a huge amount of heat, and the temperature at the edge of a forest fire, where firefighting equipment usually operates, reaches 300-700 °C. Fire engines are exposed to intense heat to extinguish forest fires. The main requirement for the design of such machines is the availability of rational thermal protection. Studies of various methods of thermal protection of cabins have showed the possibility of lowering the temperature on the inner surface of the cabin, but these methods show low efficiency. Protection of cabs from thermal radiation is not provided in the new developments of forest fire machines. It is proposed to use pre-preg coatings to protect cabins of forest fire engines. They are successfully used in spacecraft designs. Recent technologies for the production of such materials, developed recently, have significantly reduced the cost of production of these materials. It expands the possibilities of their application for other equipment subjected to intense heat exposure. The calculations have showed that the heat-protective coatings of the cabins made of pre-pregs quickly warm up to acceptable temperatures. However the use of water reserves in the tank of the car to cool the inside of the cabs provides high protection efficiency even at the limiting values of heat fluxes that occur in the fireplace. At the same time, water is not consumed; it is heated, circulating between the tank and the heat exchanger. The proposed method of protecting cabs of fire machines from thermal radiation is original one. It is a subject of further development.

On the Effectiveness of Temperature-Responsive Protective Fabric Incorporated With Shape Memory Alloy (SMA) Under Radiant Heat Exposure

2019 ◽  
Vol 38 (3) ◽  
pp. 212-224 ◽  
Author(s):  
Lijun Wang ◽  
Yehu Lu ◽  
Jiazhen He
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Protective Clothing ◽  
Thermal Protection ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Air Gap ◽  
Environment Change ◽  
Temperature Responsive ◽  
Thermal Insulating

To improve thermal protection of protective clothing, temperature-responsive protective fabrics incorporated with shape memory alloy (SMA) springs varying on four different deformation heights and five types arrangement modes were designed. The thermal protection was investigated under radiant heat exposure of 0.39 cal/cm2 s. The results indicated that the air gap between fabric layers produced by SMA springs effectively improved protective performance. The thermal protection of fabrics with different SAM arrangement modes and sizes showed different trends, and the interaction effects of arrangement mode and size were analyzed. Moreover, the optimized arrangement and size of SMA springs were suggested. The regression models were established to assess the relationship between the air gap and thermal protection. This study demonstrated that the combination of flame-resistant fabric with SMA was feasible to develop temperature-responsive protective clothing because it could improve thermal insulating property by producing intelligent air gaps that responded to environment change.

scholarly journals Thermal Protective Performance of Firefighters’ Clothing Under Low-Intensity Radiation Heat Exposure

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Hualing He ◽  
Zhicai Yu ◽  
Chunbo Zhang ◽  
Minhua Li
Keyword(s):  
Protective Clothing ◽  
Thermal Protection ◽  
Heat Exposure ◽  
Test Methods ◽  
Stored Energy ◽  
Radiation Heat ◽  
Low Intensity ◽  
Fabric System ◽  
Protective Performance ◽  
Intensity Radiation

AbstractThe stored energy provided by the fabric assemblies will greatly influence the thermal protection performance (TPP) of firefighters’ protective clothing under low-intensity radiation heat exposure. In this study, two test methods, namely radiant protective performance (RPP) and stored energy test (SET), were used to investigate the TPP of the fabric assemblies. The results indicated that TSET value was lower than TRPP value because of the release of the stored energy in the fabric assemblies after heat exposure. Increasing the fabric layer numbers, air gap between the fabric assemblies would increase the time of TRPP and TSET, indicating that the thermal stored energy weakened the TPP of the firefighters’ protective clothing. Moreover, the TRPP and TSET of the fabric system would be increased when the moisture barrier was cut in the fabric combination system. These findings suggested that stored energy should be considered in analyzing the TPP of fabric assemblies..

An improved model to analyze radiative heat transfer in flame-resistant fabrics exposed to low-level radiation

2016 ◽  
Vol 87 (16) ◽  
pp. 1953-1967 ◽  
Author(s):  
Yun Su ◽  
Jiazhen He ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Optical Properties ◽  
Thermal Energy ◽  
Thermal Exposure ◽  
Radiant Heat ◽  
Transfer Model ◽  
Radiant Heat Transfer ◽  
Flux Model ◽  
Fabric System ◽  
Improved Model

An improved heat transfer model, based on the two-flux model, in a multilayer flame-resistant fabric system with an air gap was proposed. The developed model considered the thermal radiation by absorbing, transmitting, emitting and reflecting in porous fabrics. The predicted results of the new model were compared with the previous Beer’s law model and the experimental results, and were found to be in good agreement with the experimental ones. The aim of this study is to investigate the mechanism of radiant heat transfer in the multilayer fabric system and the effects of the optical properties of flame-resistant fabric on heat transfer in the fabric system. The numerical results demonstrated that the self-emission in multilayer fabric system increases not only the rate of thermal energy transferred to human skin during thermal exposure, but also the rate of thermal energy transmitting to the ambience during cooling. The fabric’s optical properties have a complex influence on the transmitted and stored energy in multilayer protective clothing. The finding obtained in this study can provide references for the improvement of the thermal protective performance of flame-resistant fabrics.

Thermal protective performance of single-layer rib-knitted structure and its derivatives under radiant heat flux

2021 ◽  
pp. 152808372110426
Author(s):  
Sandeep K Maurya ◽  
Viraj Uttamrao Somkuwar ◽  
Hema Garg ◽  
Apurba Das ◽  
Bipin Kumar
Keyword(s):  
Heat Flux ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Air Permeability ◽  
Knitted Fabric ◽  
Radiant Heat Flux ◽  
Simple Modification ◽  
Degree Burn ◽  
Knitted Structure ◽  
Second Degree

The compact construction of fire-resistant woven clothing designed for radiant heat flux protection limits the air permeability from the skin to the environment that risks thermal stress to the wearer. Knitted fabric is well known for its comfort and transmission properties. The inevitable porosity of the knitted fabric has restrained its application in fire-protective clothing. This study attempts to apply tuck and miss elements of a knitted structure to produce a compact yet comfortable flame-retardant fabric with maximum air permeability. The effect of radiant heat exposure at the intensity of 40 kW/m2 and 61 kW/m2 is analyzed for the designed sample. The tuck and miss stitches are used to modify rib-knitted structure and the second-degree burn time estimated using Stoll’s curve. The findings of this research show that a simple modification of rib structure with incorporation of miss stitch can enhance the second-degree burn time to 30 s at the radiant heat exposure of 40 kW/m2.

scholarly journals Moisture transfer of the clothing–human body system during continuous sweating under radiant heat

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4537-4553 ◽  
Author(s):  
Manhao Guan ◽  
Simon Annaheim ◽  
Martin Camenzind ◽  
Jun Li ◽  
Sumit Mandal ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Evaporation Rate ◽  
Moisture Transfer ◽  
Thermal Protection ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Skin Surface ◽  
Multi Phase ◽  
Relationship Of ◽  
Sweat Evaporation

Mass transfer due to perspired moisture in a clothing system is critical for the understanding of thermo-physiology and thermal protection of a clothed body. Previous studies usually investigated moisture transfer without considering the effect of liquid sweating or external heat hazards. To understand the mechanisms of sweat evaporation, accumulation and dripping with continuous sweating under radiant heat, a multi-phase experiment was designed with a sweating Torso. The concept of clothed wettedness was proposed to understand sweat evaporation of the clothed body. Results showed that the evaporation rate of the clothed body increased with increasing perspiration rate and the rate increase can be explained by the material properties (e.g., material composition, hydrophilicity and evaporative resistance ([Formula: see text])), which affected the sweat accumulation ability. Results also demonstrated a dual relationship of [Formula: see text] with the evaporation rate of the clothed body. Firstly, the evaporation rate was increased for greater [Formula: see text] due to the higher moisture accumulation. Secondly, when [Formula: see text] exceeded a certain value, the evaporation rate decreased with greater [Formula: see text] due to the reduction in the mass transfer coefficient. For radiant heat exposure, evaporated sweat may condense on the skin surface, decreasing the evaporation rate and increasing the dripping rate. The sweat transfer process was also investigated in detail by the combined analysis of the sweat transfer rate and the evaporative cooling efficiency. This study provides insights into how continuous liquid sweat transfers and evaporates in the clothed body and its interaction with clothing material and environment radiant heat, contributing to the understanding of thermo-physiological burden and thermal protection of the clothed body with intensive activities.

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

2021 ◽  
pp. 0887302X2199350
Author(s):  
Jiazhen He ◽  
Ling Sun ◽  
Yehu Lu
Keyword(s):  
Thermal Radiation ◽  
Exposure Duration ◽  
Protective Clothing ◽  
High Performance ◽  
Specific Interaction ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Initial Increase ◽  
Radiation Conditions ◽  
Protective Performance

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.

scholarly journals Influence of Fabric Weave on Thermal Radiation Resistance and Water Vapor Permeability

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 525
Author(s):  
Ana Kiš ◽  
Snježana Brnada ◽  
Stana Kovačević
Keyword(s):  
High Temperatures ◽  
High Performance ◽  
Thermal Protection ◽  
Water Vapor Permeability ◽  
Radiant Heat ◽  
The Body ◽  
Vapor Permeability ◽  
Weave Structure ◽  
Fabric Structures ◽  
The Impact

In this work, aramid fibers were used to develop new, high-performance fabrics for high-temperature protective clothing. The research was based on the impact of the weave structure on fabric resistance to radiant heat. The goals of the research were primarily related to the development of new fabric structures created by the weave structure, which gives better protection of the body against high temperatures in relation to the standard weave structures that are used today. According to the results obtained it can be concluded that the fabric weave significantly affects the fabric structure, which consequently determines the effectiveness of protection against high temperatures. The justification for the use of multi-weft and strucks weave structure, which provides greater thermal protection and satisfactory breathability than commonly used weave structures, was ascertained.

scholarly journals Effect of perspired moisture and material properties on evaporative cooling and thermal protection of the clothed human body exposed to radiant heat

2018 ◽  
Vol 89 (18) ◽  
pp. 3663-3676 ◽  
Author(s):  
Manhao Guan ◽  
Agnes Psikuta ◽  
Martin Camenzind ◽  
Jun Li ◽  
Sumit Mandal ◽  
...  
Keyword(s):  
Human Body ◽  
Material Properties ◽  
Heat Dissipation ◽  
Thermal Protection ◽  
Evaporative Cooling ◽  
Thermal Characteristics ◽  
Radiant Heat ◽  
Physiological Effect ◽  
Heat Gain ◽  
Active Liquid

Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain for hydrophobic materials. In addition to fabric thermal resistance ( Rct) and evaporative resistance ( Ret), material hydrophilicity and hydrophobicity, emissivity and thickness are important when assessing metabolic heat dissipation and radiant heat gain with profuse sweating under radiant heat. The results provide experimental evidence that Rct and Ret, the general indicators of the clothing thermo-physiological effect, have limitations in characterizing thermal comfort and heat strain during active liquid sweating in radiant heat. This paper offers a more complete insight into clothing thermal characteristics and human thermal behaviors under radiant heat, contributing to the accurate evaluation of thermal stress for occupational and general individuals.

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