Moisture and clothing layers: effect of ambient temperature on heat loss and insulation
Författare
Redaktör
- Rick Burke
- Dave Heiss
- Joe Misius
- Tim Walzak
Summary, in English
In this study thermal manikin was tested with wet underwear and wrapped in 1, 2 or 7 layers of woollen rescue blankets at -15 and +10 °C. This paper discusses the issues related to possibility to improve predictions for the cases when other situations, materials or exposure temperatures are involved. A method to quantify “heat pipe” effect was proposed, and for control the calculation of dry insulation from wet tests was applied.
The measured apparent insulation, i.e. insulation based on total heat loss in wet conditions, was higher at -15 °C than at + 10 °C. That could be related to higher condensation rate in materials or suppressed evaporation. However, the measured weight loss rate (higher at 15 °C) and accumulation in layers (lower at 15 °C) did not support this conclusion. Effect could partly be related to the lower water pressure gradient between wet clothing at manikin surface and ambient air at +10 (2.5 kPa) than -15 °C (3.0 kPa).
In the case of 7 layers the highest accumulation occurred in the layers near body and in the outermost layer while only minimal accumulation of moisture was observed in the middle layers. The total accumulation was divided into ratios for each layer, and expected condensation heat to environment was based on insulation (7 layers, 1/7 of the first and 7/7 of the outer layer leaves the system). When this correction was applied to “heat pipe” effect then the corrected heat loss did lead to insulation values similar to dry tests. The method worked also for 1 and 2 layer systems with highest difference for 1 layer system. The method could be tested more accurately on a sweating cylinder/torso, where layers may be separated in order to avoid wicking or vice versa set to allow it. Using different number of layers, layer thickness and less hygroscopic materials than wool may improve estimation of the “heat pipe” effects.
Avdelning/ar
Publiceringsår
2010
Språk
Engelska
Publikation/Tidskrift/Serie
8I3M : Eighth International Meeting for Manikins and Modeling : Victoria, BC, Canada, August 22-26, 2010
Dokumenttyp
Konferensbidrag
Förlag
Sport Innovation Centre
Ämne
- Production Engineering, Human Work Science and Ergonomics
Conference name
Eighth International Meeting for Manikins and Modeling (8I3M)
Conference date
2010-08-22 - 2010-08-26
Conference place
Victoria, BC, Canada
Status
Published
Forskningsgrupp
- Thermal Environment Laboratory