MHD and heat transfer issues and characteristics for Li free surface flowsunder NSTX conditions

In the APEX study, one of the tasks focuses on the exploration and identifi cation of the attractive options and issues for flowing liquid lithium wall s in the NSTX device. In addition to constraints imposed by the machine, th e operating conditions of the flowing liquid walls along the center stack a nd divertor areas are guided by MHD and heat removal requirements. In this paper, we present important MHD and heat removal issues and analysis for th e proposed free surface lithium flows under NSTX conditions. It is shown th at of all MHD effects, the one caused by the normal magnetic field is the m ost important. The flow over the center stack area is not affected by MHD i nteraction significantly, whereas flow over the inboard divertor undergoes strong MHD drag resulting in flow thickening by several times. The flow ove r the outboard divertor is essentially stopped. The analysis shows that a f low with an inlet velocity of 2 m/s and film thickness of about 4 mm can be established to provide surface temperature less than 400 degrees C for the center stack under a projected NSTX total heating power of 10 MW operation .