Paradox: increased blood perfusion to the face <Emphasis Type="BoldItalic">enhances</Emphasis> protection against frostbite while it <Emphasis Type="BoldItalic">lowers</Emphasis> wind chill equivalent temperatures |
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Authors: | Avraham Shitzer |
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Institution: | (1) Department of Mechanical Engineering, Technion, Israel Institute of Technology, Haifa, 32000, Israel |
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Abstract: | A model of facial heat exchange in cold and windy environments is presented. The tissue is depicted as a hollow cylinder and
the model includes heat conduction and heat transport by blood circulation from the warmer core. A steady-state solution facilitating
the estimation of wind chill equivalent temperature (WCET) as a function of the effective wind velocity, air temperature and
blood perfusion rate was obtained. The results quantify and demonstrate the elevation of skin temperatures caused by increased
flow of warmer blood from the inner core to the face. Elevated facial temperatures, while enhancing protection against frostbite
and other cold-related injuries, also increase heat loss to the colder environment. Paradoxically, such elevated facial temperatures
cause WCETs, as estimated by the prevailing definition, to attain lower rather than higher values, indicating, in fact, increased
risk of frostbite. The results of this study should be useful in understanding and quantifying the effects of blood perfusion
in protection against cold-related injuries. They should also be considered in the re-evaluation and re-formulation of the
concept of wind chill, which has been a useful cold weather indicator for decades. |
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Keywords: | Wind chill Cold environment Frostbite Facial blood perfusion Convective heat transfer |
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