Total thermal radiation absorption by a single spherical droplet

The total energy absorption distribution inside a liquid droplet irradiated by blackbody emission is determined by spectral and solid angle integrations of the spectral absorption distribution given by electromagnetic theory. Results are presented for 1-100-micron radius n-decane and water droplets irradiated by a blackbody at 850-2000 K, in several axisymmetric configurations. Under spherically symmetric irradiation conditions, the water absorption results are used to verify the applicability and accuracy of the geometrical-optics approximation through comparison with those results. It is verified that the trapezoidal quadrature is usually a good approximation for spectral integration. The geometrical-optical approach leads to total absorptance values with errors larger than 10 percent for droplets smaller than 25 microns. Only the two principal bands of decane, including their wings, are needed to fairly well predict total absorption distribution in decane droplets. 24 refs