Modeling of thermal radiation of polymer coating containing hollow microspheres

Abstract

The paper deals with the effect of hollow microspheres added to paint or another polymer coating for open surfaces of a building on the heat loss due to thermal radiation. An approximate theoretical model is suggested, which is based on the spectral calculation of the radiative characteristics of a disperse system and determination of the integral flux of thermal radiation. Calculations are performed for a layer of paint with hollow glass microspheres. It is demonstrated that the microsphere shell thickness has the strongest effect on the reduction of heat loss.

Infrared radiative properties of polymer coatings containing hollow microspheres

“…When the polymer layer dries out, the distance between the microspheres decreases differently in different directions. This results in the anisotropy of the volume concentration of microspheres and in the respective anisotropy of the radiative characteristics of the medium [2]. The estimates showed that this effect is not significant and we assume the composite material to be homogeneous and isotropic.…”

“…The efficiency factors Q a , Q tr s can be calculated by the Mie theory generalized to the case of refracting and absorbing medium as described in paper [2]. In the monodisperse approximation, which is often used in engineering calculations [12], Eq.…”

“…It is a limiting case of opaque medium when the volume radiative properties don't determine the reflection of radiation from the composite material. The details of mathematics concerning the efficiency factors calculation can be found elsewhere [2,12,15].…”

“…Such materials exhibit unusual mechanical properties and high heat-insulation characteristics, which are largely defined by special features of absorption and scattering of thermal radiation by thin-walled hollow particles [1,2]. Therefore, a number of developments associated with the production of glass microspheres are oriented toward development of heat-insulating coatings.…”

“…Theoretical prediction of wide-range spectral radiative properties of the coatings containing polydisperse hollow microspheres based on traditional radiation transfer model in combination with the Mie theory for single particles (as was suggested in paper [2]) may be not adequate at high concentration of microspheres because of specific scattering effects in the volume and at the coating interface. It is known that the so-called dependent scattering effects can be observed in densely-packed disperse systems [3][4][5][6][7].…”