Fast calculating method for radiative heat shielding by polydisperse and anisotropic scattering water sprays

For the purpose of improving the calculation efficiency of shielding and attenuating thermal radiation in fire protection with polydisperse and anisotropic fine water sprays, a database of radiative properties of sprays covering the wavelength range of 1–20 μm and droplets radius range of 1–300 μm is constructed. Also a method of combining database calls for radiative properties acquisition and combined spectral radiation and gray body radiation model for solving radiative heat transfer equation is proposed, and is validated by comparing the dimensionless radiative heat flux obtained by the method and that obtained by Mie theory and spectral bands model. By accuracy and efficiency analysis, the database calls for getting radiative properties are found to be accurate and with high efficiency. The accuracy of Spectral-Grey model depends on the wavelength range of gray body assumption. Choosing reasonable gray body assumption bands according to the droplets sizes and loading will not only guarantee the calculation accuracy at an acceptable level, but also reduce the CPU time significantly.