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Apparent latent heat of evaporation from clothing: attenuation and “heat pipe” effects

Havenith, George; Richards, Mark; Wang, Xiaoxin; Bröde, Peter; Candas, Victor; den Hartog, Emiel; Holmér, Ingvar LU ; Kuklane, Kalev LU ; Meinander, Harriet and Nocker, Wolfgang (2008) In Journal of Applied Physiology 104(1). p.142-149
Abstract
Investigating claims that a clothed person’s mass loss does not always represent their evaporative heat loss (EVAP), a thermal manikin study was performed measuring heat balance components in more detail than human studies would permit. Using clothing with different levels of vapor permeability and measuring heat losses from skin controlled at 34°C in ambient temperatures of 10, 20, and 34°C with constant vapor pressure (1 kPa), additional heat losses from wet skin compared with dry skin were analyzed. EVAP based on mass loss (Emass) measurement and direct measurement of the extra heat loss by the manikin due to wet skin (Eapp) were compared. A clear discrepancy was observed. Emass overestimated Eapp in warm environments, and both under... (More)
Investigating claims that a clothed person’s mass loss does not always represent their evaporative heat loss (EVAP), a thermal manikin study was performed measuring heat balance components in more detail than human studies would permit. Using clothing with different levels of vapor permeability and measuring heat losses from skin controlled at 34°C in ambient temperatures of 10, 20, and 34°C with constant vapor pressure (1 kPa), additional heat losses from wet skin compared with dry skin were analyzed. EVAP based on mass loss (Emass) measurement and direct measurement of the extra heat loss by the manikin due to wet skin (Eapp) were compared. A clear discrepancy was observed. Emass overestimated Eapp in warm environments, and both under and overestimations were observed in cool environments, depending on the clothing vapor permeability. At 34°C, apparent latent heat ((lambda)app) of pure evaporative cooling was lower than the physical value ((lambda); 2,430 J/g) and reduced with increasing vapor resistance up to 45%. At lower temperatures, (lambda)app increases due to additional skin heat loss via evaporation of moisture that condenses inside the clothing, analogous to a heat pipe. For impermeable clothing, (lambda)app even exceeds (lambda) by four times that value at 10°C. These findings demonstrate that the traditional way of calculating evaporative heat loss of a clothed person can lead to substantial errors, especially for clothing with low permeability, which can be positive or negative, depending on the climate and clothing type. The model presented explains human subject data on EVAP that previously seemed contradictive. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
heat balance, evaporative cooling efficiency, condensation, sweat evaporation, protective clothing
in
Journal of Applied Physiology
volume
104
issue
1
pages
142 - 149
publisher
American Physiological Society
external identifiers
  • wos:000252398700018
  • scopus:38349031001
ISSN
1522-1601
DOI
10.1152/japplphysiol.00612.2007
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
62ced885-27b5-4236-b0c9-dea44caab57c (old id 592908)
date added to LUP
2008-02-13 16:15:45
date last changed
2017-07-30 03:51:50
@article{62ced885-27b5-4236-b0c9-dea44caab57c,
  abstract     = {Investigating claims that a clothed person’s mass loss does not always represent their evaporative heat loss (EVAP), a thermal manikin study was performed measuring heat balance components in more detail than human studies would permit. Using clothing with different levels of vapor permeability and measuring heat losses from skin controlled at 34°C in ambient temperatures of 10, 20, and 34°C with constant vapor pressure (1 kPa), additional heat losses from wet skin compared with dry skin were analyzed. EVAP based on mass loss (Emass) measurement and direct measurement of the extra heat loss by the manikin due to wet skin (Eapp) were compared. A clear discrepancy was observed. Emass overestimated Eapp in warm environments, and both under and overestimations were observed in cool environments, depending on the clothing vapor permeability. At 34°C, apparent latent heat ((lambda)app) of pure evaporative cooling was lower than the physical value ((lambda); 2,430 J/g) and reduced with increasing vapor resistance up to 45%. At lower temperatures, (lambda)app increases due to additional skin heat loss via evaporation of moisture that condenses inside the clothing, analogous to a heat pipe. For impermeable clothing, (lambda)app even exceeds (lambda) by four times that value at 10°C. These findings demonstrate that the traditional way of calculating evaporative heat loss of a clothed person can lead to substantial errors, especially for clothing with low permeability, which can be positive or negative, depending on the climate and clothing type. The model presented explains human subject data on EVAP that previously seemed contradictive.},
  author       = {Havenith, George and Richards, Mark and Wang, Xiaoxin and Bröde, Peter and Candas, Victor and den Hartog, Emiel and Holmér, Ingvar and Kuklane, Kalev and Meinander, Harriet and Nocker, Wolfgang},
  issn         = {1522-1601},
  keyword      = {heat balance,evaporative cooling efficiency,condensation,sweat evaporation,protective clothing},
  language     = {eng},
  number       = {1},
  pages        = {142--149},
  publisher    = {American Physiological Society},
  series       = {Journal of Applied Physiology},
  title        = {Apparent latent heat of evaporation from clothing: attenuation and “heat pipe” effects},
  url          = {http://dx.doi.org/10.1152/japplphysiol.00612.2007},
  volume       = {104},
  year         = {2008},
}