Abstract
The prediction accuracy of the Predicted Heat Strain (PHS) model is affected by the correction approaches of static thermophysical properties of clothing considering the pumping effects of wind and body movement. In this study, a comparison of different correction algorithms for three types of clothing and their influence on the heat strain predicted by the PHS model was carried out with experimental data obtained from the literature. Results show that the dynamic insulation values calculated by ISO 9920 corrections are larger than those obtained by ISO 7933 when the static insulation values are higher than 0.4 clo, but when the static values are lower than 0.4 clo, it varies contrarily. The dynamic evaporative resistance values calculated with ISO 9920 equations are larger than those with ISO 7933. The prediction accuracy of the PHS model with ISO 9920 corrections and the addition of the walking speed input parameter can be improved for normal clothing (NC) in a hot environment and high clothing insulation. For specialized, insulating, cold weather clothing (SC), ISO 7933 corrections with an added walking speed input parameter to the PHS model have a good prediction precision.
Highlights
Heat strain is usually faced by people in various occupations, such as firefighters, cooks, construction workers, and soldiers
For normal clothing (NC) (Icl = 0.6, 0.8, 1 clo), the dynamic clothing insulation values calculated, consistent with ISO 9920, appeared to be higher than those obtained by applying ISO 7933 correction formulas, and the maximum difference percentage was 15%, Figure 1a
These results indicated that the predicted rectal temperature was slightly lower than the observed value, the rmsd of the rectal temperatures predicted by Predicted Heat Strain (PHS) model with ISO 7933, ISO 9920, or the Lu correction formula were far lower than the standard deviation (SD) of experimental data (0.24), which meant those three algorithms all had a good prediction accuracy
Summary
Heat strain is usually faced by people in various occupations, such as firefighters, cooks, construction workers, and soldiers. It has an impact on the work efficiency, the productivity, and may even threaten life due to the risk of heat disorders that can be affected by the metabolic rate, hot environments, or clothing factors. The Predicted Heat Strain (PHS) model may be the most feasible index examined for the assessment of the potential health problems related to physiological strain [1], and it is specified by ISO 7933-2004 [2]. The PHS model is based on human body heat balance equations and can be used to predict minute-by-minute rectal temperatures and sweat rates.
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