Comparison of correction factor for both dynamic total thermal insulation and evaporative resistance between ISO 7933 an
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(2020) 39:23
ORIGINAL ARTICLE
Open Access
Comparison of correction factor for both dynamic total thermal insulation and evaporative resistance between ISO 7933 and ISO 9920 Satoru Ueno
Abstract Background: Thermal insulation and evaporative resistance of clothing are the physical parameters to quantify heat transfer and evaporative dissipation from the human body to the environment, respectively. Wind and body movement decrease thermal insulation and evaporative resistance of clothing, which is represented as correction factors for dynamic total thermal insulation (CFi) and evaporative resistance (CFe), respectively. Then, CFi and CFe are parts of the key parameters to predict heat strain of workers by computer simulation. The objective of this study was to elucidate the difference of CFi and CFe between ISO 7933 and ISO 9920 and compare the difference of predicted rectal temperature, water loss, and exposure time limit calculated by using each correction factor. Methods: CFi of ISO 7933 (CFi7933) and ISO 9920 (CFi9920), and CFe of ISO 7933 (CFe7933) and two kinds of CFe of ISO 9920 (CFe9920a, CFe9920b) were compared in terms of relative air velocity, walking speed for three kinds of thermal insulation of clothing. Next, two modified predicted heat strain (PHS) models were developed: modified PHS integrated with CFi9920 and CFe9920a (PHSmA) and modified PHS integrated with CFi9920 and CFe9920b (PHSmB). We calculated the rectal temperature, water loss, and exposure time limit by PHS, PHSmA, and PHSmB and compared the results. Results: CFi7933 and CFi9920 were almost similar in terms of Var and walking speed, while CFe9920a and CFe9920b were larger than CFe7933 when Var was more than 1.0 m·s−1. Intrinsic clothing insulation (Icl) diminished the effects of Var on CFi7933, CFi9920, CFe7933, and CFe9920b. However, CFe9920a was not influenced by Icl. The predicted rectal temperature and water loss difference were larger between PHS and PHSmA as CFe difference got larger. The duration time when limit of rectal temperature of 38 °C was reached (DlimTre38) calculated by PHS was significantly longer than PHSmA, PHSmB at higher Var. Conclusions: Precise correction factors for evaporative resistance are required to predict rectal temperature, water loss, and work-time limits. Keywords: Predicted heat strain (PHS), Thermal insulation, Evaporative resistance, Correction factor
Correspondence: [email protected] Japan Organization of Occupational Health and Safety, National Institute of Occupational Safety and Health, 6-21-1 Nagao, Tama-ku, Kawasaki, Kanagawa 214-8585, Japan © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included
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