NUMERICAL INVESTIGATION OF CRITICAL HEAT FLUX UNDER THE EFFECT OF DIFFERENT OPERATING CONDITIONS IN FLOW BOILING

The influences of inlet mass flux, wall heat flux magnitude and non-uniform wall heat flux profile on the critical heat flux and its location in a vertical round tube are studied numerically. The extended RPI wall boiling model coupled with the two fluid Eulerian-Eulerian multiphase model are utilized. The base case is validated by comparison of obtained wall temperature against the available experimental and numerical data. The obtained results demonstrate that increment in applied wall heat flux leads to generate more vapor in the tube. Thus the wall superheat increases and causes to occurrence of critical heat flux. When the heated wall is subjected to the non-uniform heat flux profile the wall superheat increases and the location of dry-out condition shifts towards the tube inlet compared to uniform wall heat flux case.