STP900: Efficacy of Heat Exchange by Use of a Wettable Cover over Chemical Protective Garments

    Gonzalez, RR
    Chief, Biophysics Branch, biophysics consultant, research physical scientist, research physiologist, and director, U.S. Army Research Institute of Environmental Medicine, Natick, MA

    Breckenridge, JR
    Chief, Biophysics Branch, biophysics consultant, research physical scientist, research physiologist, and director, U.S. Army Research Institute of Environmental Medicine, Natick, MA

    Levell, CA
    Chief, Biophysics Branch, biophysics consultant, research physical scientist, research physiologist, and director, U.S. Army Research Institute of Environmental Medicine, Natick, MA

    Kolka, MA
    Chief, Biophysics Branch, biophysics consultant, research physical scientist, research physiologist, and director, U.S. Army Research Institute of Environmental Medicine, Natick, MA

    Pandolf, KB
    Chief, Biophysics Branch, biophysics consultant, research physical scientist, research physiologist, and director, U.S. Army Research Institute of Environmental Medicine, Natick, MA

    Pages: 20    Published: Jan 1986


    Abstract

    A continuing effort is being made to reduce the dangers of heat exhaustion for persons working in heat with impermeable chemical protective garments (CPGs). One approach that appears feasible is the use of a wettable cover surrounding the CPG. The efficacy of evaporation of the heat extracted is a function of the evaporative heat transfer coefficient, he (in watts per square metre per torr), and the gradient, ΔPsk, of the saturation vapor of pressures (in torrs) between the wettable cover surface, Pc, and the ambient air, Pw. The he value is dependent on wind movement [based on a convective heat transfer coefficient, (in watts per square metre kelvin)], the appropriate Lewis numbers for air, La (2.2 K/torr), and the layers of wettable covers, Llay. Copper manikin and experimental studies showed that (1) when ΔPsk is reduced, as in severe hot and humid conditions, evaporative heat removal is minimal; (2) model predictions for CPG gave supplementary cooling (increased skin heat loss) ranging from 40 W at 35°C, Pw = 29.5 torr, and low air movement, to almost 200 W for a hot and dry environment of 50°C, 18 torr, with a 5-m/s wind. The predicted water requirements to maintain the cover at 100% wetness under these conditions ranged from 3 to 32 g/min, respectively.

    Keywords:

    wettable cover, impermeable garment, evaporative heat loss, cooling efficiency, clothing insulation, clothing temperature, heat stress prediction, protective clothing


    Paper ID: STP17339S

    Committee/Subcommittee: F23.96

    DOI: 10.1520/STP17339S


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