Three-dimensional heat transfer and fluid flow in the modern discharge lamp

It is well established that heat transfer and convection characteristics can substantially affect the light quality as well as life expectancy of a discharge lamp. However, the present level of understanding of these processes is not adequate to guide engineering design due to the combined physical and geometrical complexities involved. Efforts have been made both experimentally and theoretically in the present work to identify the roles of different heat transfer mechanisms between the arctube and the jacket of a modern discharge lamp. By solving the three-dimensional Navier-Stokes equations and a simplified radiation model in curvilinear coordinates, good agreement between measurements and predictions in terms of the wall temperature profiles have been obtained. Both convection and radiation modes are found important in overall heat transfer. Interplays between temperature gradients and geometrical variations around the arctube, and their impact on the structure of the convection field inside the jacket have also been revealed in a detailed manner by the theoretical model.