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Transport Phenomena in Thermal Engineering. Volume 2

1-56700-015-0 (Print)


Wen-Jei Yang
Department of Mechanical Engineering and Applied Mechanics University of Michigan, Ann Arbor, Michigan 48109-2125, U.S.A.

Nengli Zhang
Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, MI 48109, USA


Polar bears live on top of the world (north of the Arctic Circle) where a cold wind moans and temperatures plunge well below freezing during the wind. The secret to survive is that they wear a unique coat which actually consists of two fur coats. The outer coat is made up by long individual hairs which are colorless hollow tubes. It traps a layer of air to provide further insulation for the body. Then, there is a dense layer of short under-hairs. The under-hair is so thick that water never reaches the skin. The coat hides another secret - black skin to absorb and retain the radiant heat that is transfered down through total internal reflection in the hollow hairs.
This paper introduces the next generation in thermal insulation (i.e., thermal protection system) based on the bionics of polar bear's fur coats. It functions like a perfect solar heat collector with insolation and yet is a perfect thermal insulator. A theoretical model is developed to simulate the functioning of solar heat absorbing/thermal insulation of the biological system. Results are obtained for polar bears under different metabolic activities and ambient conditions. The application of the biological system to the next generation in insulation is discussed.