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Question (Category: mechanical engineering)
the wind chill , which is experienced on a cold, windy day,is related to increased heat transfer from exposed human skin tothe surrounding atmosphere.consider a layer of fatty tissuethat is 3 mm thick and whose interior surface is maintained at atemperature of 36186c.on a calm day the convection heattransfer coefficient at the outer surface is 25w(m 2 8226k), but with 30kmh winds it reaches 65w(m 2 8226k).in both cases the ambient airtemperature is -15186c. k value for fatty tissue is 0.2wm k. (a) what is the ratio of the heat loss perunit area from the skin for the calm day to that for the windyday? (b) what will be the skin outer surfacetemperature for the calm day?for the windy day? (c) what temperature would the air have toassume on the calm day to produce the same heat loss occurring withthe air temperature at -15186c on the windy day? answers given (a) q x,c q x,w @ 0.552 (b) (t skin ) calm =22.1 176 c and(t skin ) windy =10.8 176 c (c) t 165 =-56.3 176 c


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