In one version of the model, the researchers incorporated so-called black-body shields, which absorb all of the radiation that strikes them. In a second version, opaque grey-body shields were used. "A grey body has some transmission and reflection as well," Simonis explains.
Simonis and her colleagues found that as the reflectivity of the radiative shields increased, the rate of heat transfer between the hot and cold thermostat was dramatically reduced. Adding more shields also dramatically reduced the energy loss. All together, the model suggests that the repeated backscattering of infrared light between radiative shields, like individual hairs and barbed feathers, could be the primary mechanism for the thermal insulation properties of fur and feathers.
The light scattering properties of animals' coats can also have dual purposes, Simonis notes. With the right structure, fur and feathers can generate efficient thermal insulation in the far infrared range while also scattering visible light to produce a white appearance in the visible wavelength range. "This is particularly useful to animals, such as mammals and birds, that live in snowy areas," Simonis says, as it provides them with both warmth and camouflage against the white snow.
For humans, focusing on ways to minimize radiative heat loss could lead to the development of new types of ultrathin insulation. "The idea is to multiply the interaction of electromagnetic waves with grey bodies reflecting bo
|Contact: Angela Stark|
The Optical Society