Thermal Analysis on Flat-Plate-Type Divertor Based on Subcooled Flow Boiling Critical Heat Flux Data Against Inlet Subcooling in Short Vertical Tube

The critical heat fluxes (CHFs) and the heat transfer coefficients (HTCs) in subcooled flow boiling were applied to a thermal analysis of the flat-plate-type divertor of a helical-type fusion experimental device, which is a Large Helical Device (LHD) located in the National Institute for Fusion Science (NIFS), Japan. The incident CHF, $qcr,inc$⁠, for the divertor plate with the cooling tube diameter, $d$⁠, of $10mm$ and the plate width, $w$⁠, ranging from 16 to $30mm$ were numerically analyzed based on the measured CHFs, $qcr,sub$⁠, and HTCs for the test tube inner diameter, $d$⁠, of $9mm$ and the heated length, $L$⁠, of 48 to $149mm$⁠. The peripheral distributions of the surface heat flux and the surface temperature in the cooling tube were obtained. Numerical solutions of $qcr,inc$ become larger with a decrease in $w∕d$ at a fixed $L$⁠. It is confirmed that the ratio of the one-side heat loading data, $qcr,inc$⁠, to the uniform heat loading data, $qcr,sub$⁠, can be represented as the simple equation based on the numerical solutions. The values of the $qcr,inc$ for the tube length of 50, 100, and $150mm$ were estimated with various $w∕d$ at a higher pressure.