Advanced

Non-evaporative effects of a wet mid layer on heat transfer through protective clothing

Bröde, Peter; Havenith, George; Wang, Xiaoxin; Candas, Victor; den Hartog, Emiel A.; Griefahn, Barbara; Holmér, Ingvar LU ; Kuklane, Kalev LU ; Meinander, Harriet and Nocker, Wolfgang, et al. (2008) In European Journal of Applied Physiology 104(2). p.341-349
Abstract
In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 °C, 80% RH and 0.5 ms-1 air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 Wm-2), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity.

In the... (More)
In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 °C, 80% RH and 0.5 ms-1 air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 Wm-2), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity.

In the experiments with 8 males, each subject participated in two sessions with the mid underwear layer either dry or wetted, where they stood still for the first 30 minutes and then performed treadmill work for 60 minutes. Reduced heat strain due to lower insulation with the wetted mid layer was observed with decreased microclimate and skin temperatures, lowered sweat loss and cardiac strain. Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m2 °C W-1 (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer’s increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing. (Less)
Please use this url to cite or link to this publication:
author
, et al. (More)
(Less)
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
moisture, skin temperature, clothing insulation, sweating, conduction
in
European Journal of Applied Physiology
volume
104
issue
2
pages
341 - 349
publisher
Springer
external identifiers
  • wos:000258609300027
  • scopus:50449087634
ISSN
1439-6327
DOI
10.1007/s00421-007-0629-y
project
EU project “THERMPROTECT, Assessment of Thermal Properties of Protective Clothing and Their Use”, contract G6RD-CT-2002-00846
language
English
LU publication?
yes
id
56858a49-df41-42e0-9d7b-ff2cf5f245fa (old id 631735)
date added to LUP
2007-12-03 13:50:37
date last changed
2017-09-10 03:33:10
@article{56858a49-df41-42e0-9d7b-ff2cf5f245fa,
  abstract     = {In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 °C, 80% RH and 0.5 ms-1 air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 Wm-2), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity.<br/><br>
In the experiments with 8 males, each subject participated in two sessions with the mid underwear layer either dry or wetted, where they stood still for the first 30 minutes and then performed treadmill work for 60 minutes. Reduced heat strain due to lower insulation with the wetted mid layer was observed with decreased microclimate and skin temperatures, lowered sweat loss and cardiac strain. Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m2 °C W-1 (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer’s increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing.},
  author       = {Bröde, Peter and Havenith, George and Wang, Xiaoxin and Candas, Victor and den Hartog, Emiel A. and Griefahn, Barbara and Holmér, Ingvar and Kuklane, Kalev and Meinander, Harriet and Nocker, Wolfgang and Richards, Mark},
  issn         = {1439-6327},
  keyword      = {moisture,skin temperature,clothing insulation,sweating,conduction},
  language     = {eng},
  number       = {2},
  pages        = {341--349},
  publisher    = {Springer},
  series       = {European Journal of Applied Physiology},
  title        = {Non-evaporative effects of a wet mid layer on heat transfer through protective clothing},
  url          = {http://dx.doi.org/10.1007/s00421-007-0629-y},
  volume       = {104},
  year         = {2008},
}