Mathematical Foundation and the Boundary Conditions Encountered in Laser EnergyDiffusion in a Solid and Skin Simulant Temperature Rise

摘要

The energy diffusion from a laser beam in a solid was critically analyzed and thesolutions were applied to the problem of temperature rise of a skin simulant irradiated with a laser beam. The solutions involved two sets of contradicting boundary conditions: The zero surface heat flux vs the constant surface heat flux at the boundary. It is shown that the constant surface heat flux boundary condition in the conventional solution of the diffusion equation is unrealistic for a laser beam. Justification for the zero surface heat flux boundary condition for laser irradiation is presented along with the calculations for the temperature rise of a laser irradiated skin simulant. For laser exposures of 1000, 400, 100, 50 and 20 uS, the values of the surface temperature rise given by the constant surface heat flux solutions are higher by a factor of 2.2, 2.8, 4.9, 6.6 and 9.8, respectively, than that given by the zero surface heat flux solution. The analysis holds for the general case of other irradiated solids.