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In order to improve thermal endurance, mechanical durability and ventilation performance in a headlamp, it is important to understand heat transfer and flow in an automotive headlamp. Especially in a design stage, understanding natural convection inside the headlamp will make it possible to shorten its development period, which can be fulfilled by Computational Fluid Dynamics (CFD). In the present study, a newly-developed method called Surface Heat Transfer (SHT) method, that is a unique technique for making an accurate estimate of temperature and velocity in the automotive headlamp without involving the couple of the fluid mechanics and the structural mechanics (the coupled fluid solid interaction), was investigated for practical use. An evaluation of SHT method was performed, and CFD results were compared with the experimental results. Consequently, the temperature results by CFD were within ±10 degrees as compared with the experimental results.

Since an automotive headlamp is very complicated structure, CFD (Computational Fluid Dynamics) had the problem of being very difficult. Especially, if radiation is taken into consideration, the memory required for calculation is huge. In the present study, the first aim was to develop the new calculation technology that was called FSI-DM, that is a unique technique, in which the calculation mesh generated in the fluid were made discontinuous on the solid and fluid surface. In this FSI-DM, radiative heat transfer was calculated with using the coarse mesh generated on the solid surface to reduce memory size in order to use practical, and it enable us to predict velocity and temperature on the inner parts of an automotive headlamp comparatively accurately. Next, FSI-DM was further extended so that it would be able to be applied for moisture condensation on the lens surface.