The effect of particles size distribution on aesthetic and thermal performances of polydisperse TiO ₂ pigmented coatings: Comparison between numerical and experimental results

A new approach in designing pigmented coatings considering both visual and thermal concerns was introduced by authors in previous works. The objective was to design a pigmented coating with dark appearance which can stay cool while exposed to sunlight. This behavior can be achieved by coating a typical black substrate with a pigmented coating with controlled size and concentration of particles and coating thickness. In present work, the spectral behaviour of polydisperse TiO ₂ pigmented coatings was studied. The radiative properties of polydisperse TiO ₂ powders were evaluated and the radiative transfer in the pigmented coating was modelled using the radiation element method by ray emission model (REM ²). The effects of particles size distribution on spectral reflectivity, optimization parameter, and color coordinates were discussed. The results of numerical calculation were validated by experimental reflectivity measurements of several TiO ₂ pigmented coating samples made from two different TiO ₂ powders with different size distributions of particles. The results show that our model can reasonably predict the spectral reflectivity of TiO ₂ pigmented coating samples. Moreover, the results of optimized monodisperse TiO ₂ pigmented coatings were again validated.