Analytical study of the heat loss attenuation by clothing on thermal manikins under radiative heat loads

For wearers of protective clothing in radiation environments there are no quantitative guidelines available for the effect of a radiative heat load on heat exchange. Under the European Union funded project ThermProtect an analytical effort was defined to address the issue of radiative heat load while wearing protective clothing. As within the ThermProtect project much information has become available from thermal manikin experiments in thermal radiation environments, these sets of experimental data are used to verify the analytical approach. The analytical approach provided a good prediction of the heat loss in the manikin experiments, 95% of the variance was explained by the model. The model has not yet been validated at high radiative heat loads and neglects some physical properties of the radiation emissivity. Still, the analytical approach provides a pragmatic approach and may be useful for practical implementation in protective clothing standards for moderate thermal radiation environments

Infrared radiation effects on heat loss measured by a thermal manikin wearing protective clothing

The main objective of the EU funded research project THERMPROTECT is to provide basic data and models on "Thermal properties of protective clothing and their use" for improving the assessment of heat stress (3). One work package studies the effects of thermal radiation utilising a stepwise experimental approach comprising flat plate material tests, manikin experiments and human trials. This paper deals with manikin experiments on the effects of far infrared heat radiation (FIR), considering aspects related to the reflectivity of the clothing, the number of clothing layers and the radiated body surface area

Modelling the metabolic effects of protective clothing

Protective clothing is worn in many industrial and military situations. Although worn for protection from one or more hazards, protective clothing can add significantly to the metabolic (energy) cost of work. Suggestions put forward as to the mechanisms behind the observed increases include, the additional clothing weight of the protective garments, possible friction between the number of layers that must be worn and restriction of movement due to clothing bulk. However, despite much speculation, these areas have not received much investigation. Wearing protective clothing from a range of industries and with quite different characteristics for example weight, bulk and stiffness significantly increased metabolic rate when walking, stepping and completing an obstacle course activity. Increases in the metabolic rate of up to 20% above control conditions (lightweight tracksuit and trainers worn) were seen. A number of clothing properties were then investigated to try and understand the causes of these recorded metabolic rate increases. Clothing bulk was measured at 3 sites, upper arm, torso and thigh. The stiffness of the clothing was also calculated, using a method which measured the clothing drape of the sleeve, main body of the garment and trouser leg. A multiple regression carried out on the data showed body weight to be the best predictor of absolute metabolic increases across all work modes. For the % increase in metabolic rate total clothing weight was the best predictor. Torso bulk was negatively correlated with the increased metabolic rate for walking and stepping and the overall average, whereas leg bulk was a significant predictor of an increased stepping metabolic rate and leg stiffness a significant predictor for the obstacle course work mode

Moisture accumulation in sleeping bags at-7 degrees C and-20 degrees C in relation to cover material and method of use

Moisture accumulation in sleeping bags during extended periods of use is detrimental to thermal comfort of the sleeper, and in extreme cases may lead to sleep loss and hypothermia. As sub-zero temperatures were expected to affect vapour resistance of microporous membranes, the effect of using semipermeable and impermeable rain covers for sleeping bags on the accumulation of moisture in the bags during 6 days of use at − 7°C and 5 days at − 20°C were investigated. In addition, the routine of shaking off hoarfrost from the inside of the cover after the sleep period as a preventive measure for moisture accumulation was studied. Moisture accumulation (ranging from 92 to 800 grams) was found to be related to the vapour resistance of the materials used. The best semipermeable material gave the same moisture build-up as no cover at − 7°C, though build-up increased substantially at − 20°C. Shaking off the hoarfrost from the inside of the cover after each use was beneficial in preventing a high moisture build-up. It was concluded that semi-permeable cover materials reduce moisture accumulation in sleeping bags at moderate sub-zero temperatures, but in more extreme cold (− 20°C) the benefits are reduced in comparison to routinely shaking frost from impermeable covers. Compared to fixed impermeable covers, the benefits of all semi-permeable covers are large. For long-term use without drying facilities, the differences observed do favour the semi-permeable covers above impermeable ones, even when regularly removing the hoar frost from the inside in the latter