Clothing evaporative heat resistance - Proposal for improved representation in standards and models

Clothing evaporative heat resistance - Proposal for improved representation in standards and models

Havenith, G.
Holmér, I.
den Hartog, E.A.
Parsons, K.C.
TNO Human Factors Research Institute

1999

Clothing heat and vapour resistances are important inputs for standards and models dealing with thermal comfort, heat- and cold-stress. A vast database of static clothing heat resistance values is available, and this was recently expanded with correction equations to account for effects of movement and wind on the static value of heat resistance in order to obtain the dynamic heat resistance of clothing ensembles. For clothing vapour resistance, few data were available so far. Indices for vapour permeability (i(m)) and reduction factors for vapour transfer (F(pcl)) of clothing were used instead, using a relation between heat and vapour resistance to derive the clothing vapour resistance from the value for clothing heat resistance. This paper reviews the two commonly used approaches (i(m) and F(pcl)), as well as five alternative approaches to the problem. The different approaches were evaluated for their accuracy and their usability.The present paper shows that the currently used relations are not adequate when the wearer of the clothing starts moving, or is exposed to wind. Alternative approaches are shown to improve the determination of dynamic clothing vapour resistance, though some are thought to be too complex. An empirical description of the relation between the clothing permeability index (i(m)) and the changes in clothing heat resistance due to wind and movement was selected as the most promising method for deriving clothing vapour resistance. For this method the user needs to know the static heat resistance, the static i(m) value of the clothing and the wind- and movement-speed of the wearer. This method results in a predicted maximal decrease in clothing vapour resistance by 78%, when clothing heat resistance is reduced by 50%, which is consistent with theoretical expectations and available data. Copyright (C) 1999 British Occupational Hygiene Society. A review is carried out on the two commonly used approaches as well as five alternative approaches to the issues of clothing heat and vapor resistances. The different approaches are evaluated for their accuracy and usability. It is shown that the currently used relations are not adequate when the wearer of the clothing starts moving, or is exposed to wind. Alternative approaches are shown to improve the determination of dynamic clothing vapor resistance.

Clothing
Clothing resistance
Heat transfer
International standards
Vapour transfer
Evaporation
Vapors
Wind effects
Dynamic clothing vapour resistance
Evaporative heat loss
Static clothing heat resistance
Thermal balance
Thermal comfort
Vapor permeability
Protective clothing
Wweating
Thermodynamics
Bias (Epidemiology)
Body Temperature Regulation
Heat Stress Disorders
Humans
Humidity
Materials Testing
Models, Biological
Movement
Occupational Diseases
Permeability
Protective Clothing
Reproducibility of Results
Thermodynamics
Volatilization
Wind

http://resolver.tudelft.nl/uuid:71cc7faf-bd34-4a6e-90de-d17eebe19afb

235076

Elsevier Science Ltd, Exeter, United Kingdom

0003-4878

Annals of Occupational Hygiene, 43 (5), 339-346

article