6 September 2017 Super-cool paints: optimizing composition with a modified four-flux model
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Abstract
The scope for maximizing the albedo of a painted surface to produce low cost new and retro-fitted super-cool roofing is explored systematically. The aim is easy to apply, low cost paint formulations yielding albedos in the range 0.90 to 0.95. This requires raising the near-infrared (NIR) spectral reflectance into this range, while not reducing the more easily obtained high visible reflectance values. Our modified version of the four-flux method has enabled results on more complex composites. Key parameters to be optimized include; fill factors, particle size and material, using more than one mean size, thickness, substrate and binder materials. The model used is a variation of the classical four-flux method that solves the energy transfer problem through four balance differential equations. We use a different approach to the characteristic parameters to define the absorptance and scattering of the complete composite. This generalization allows extension to inclusion of size dispersion of the pigment particle and various binder resins, including those most commonly in use based on acrylics. Thus, the pigment scattering model has to take account of the matrix having loss in the NIR. A paint ranking index aimed specifically at separating paints with albedo above 0.80 is introduced representing the fraction of time at a sub-ambient temperature.
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Marc A. Gali , Marc A. Gali , Matthew D. Arnold, Matthew D. Arnold, Angus R. Gentle, Angus R. Gentle, Geoffrey B. Smith, Geoffrey B. Smith, } "Super-cool paints: optimizing composition with a modified four-flux model", Proc. SPIE 10369, Thermal Radiation Management for Energy Applications, 103690A (6 September 2017); doi: 10.1117/12.2273548; https://doi.org/10.1117/12.2273548
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