Analyze two-dimensional heat transfer of ultrafast laser heated thin films under siz effects

An improved dual-phase-lagging (DPL) model which reflects size effects caused by nanostructures is utilized to investigate the two-dimensional thermal conduction of nano silicon films irradiated by ultrafast laser. The integral transformation method is used to solve the conduction governing equation based on the improved DPL model. The variation of the internal temperature along the thickness direction and the radial direction of the thin film is analyzed. We find that the temperature increases rapidly in the heated region of the film, and as time goes by, the energy travels from the heated end to another end in a form of wave. Although both the improved DPL model and the DPL model can obtain similar thermal wave temperature fields, the temperature distribution in the film obtained by the improved DPL model is relatively flat, especially for high Knudsen number. Under the same Knudsen number, the temperature obtained by the two-dimensional improved DPL model is higher than that obtained by the one-dimensional model, and the temperature difference becomes larger and larger as time elapses.