Predicting the Risk of Freezing the Skin
Abstract
It is well known that wind increases the risk of frostbite during exposure in a cold climate. The explanation is that increased airspeeds enhance heat transfer from the body. This effect was quantified by Siple and Passel in the 1940's. They measured the time needed for water, inside a cylinder, to freeze during exposure to various combinations of air speed and temperature. From these data, they developed the so-called windchill index (WCI) for predicting the heat transfer from nude body parts. Later WCI was also expressed as 'equivalent temperature (T(sub c)) However, a reexamination of the Siple and Passel data has shown that WCI (and T(sub c)) does not correctly describe the wind induced heat transfer. As charts based on WCI and T(sub c) are frequently used to express cold weather severity these indices should be corrected. Another shortage is that important parameters for predicting windchill are limited to air speed and temperature. A previously presented skin-frostbite risk model has been developed further, now also allowing simulation of wet skin and solar radiation. The model suggests that the risk for finger frostbite increases from 30 to 70% after wetting the skin when the air speed and temperature is 6, 8 m/s and - 15 deg C, respectively. This prediction is similar to experimental results found in the literature. There is a common opinion that windchill skin injuries are rare in the Antarctic during the summer. It is estimated that solar radiation corresponds to 5 to 10 deg C higher air temperature. These values are much the same as those suggested by the model at solar intensities common during the Antarctic summer. Another opinion is that time spent in cold weather regions reduces the risk of skin frostbite considerably. This adaptation has been found to reduce the risk of finger frostbite from 74% (1st year men) to 29% (2nd year men).
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2002
- Accession Number
- ADP012437
Entities
People
- Ulf Danielsson
Organizations
- Swedish Defence Research Agency