SYMPOSIA PAPER Published: 01 January 1986
STP17339S

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

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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.

Author Information

Gonzalez, RR
U.S. Army Research Institute of Environmental Medicine, Natick, MA
Breckenridge, JR
U.S. Army Research Institute of Environmental Medicine, Natick, MA
Levell, CA
U.S. Army Research Institute of Environmental Medicine, Natick, MA
Kolka, MA
U.S. Army Research Institute of Environmental Medicine, Natick, MA
Pandolf, KB
U.S. Army Research Institute of Environmental Medicine, Natick, MA
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Details
Developed by Committee: F23
Pages: 515–534
DOI: 10.1520/STP17339S
ISBN-EB: 978-0-8031-4967-0
ISBN-13: 978-0-8031-0461-7