[en] Thermal evaluation of a cask using three-dimensional models is especially difficult if the spent fuel assemblies are modeled explicitly and included in the analysis. These assembly elements are modeled as solids with homogenous 'smeared' or 'effective properties'. This solid method can predict the peak cladding temperatures of casks with reasonable accuracy. One of the solid methods is CFD simulation on transverse cross-section of a spent fuel assembly. The temperatures of a spent fuel assembly were calculated by using the conduction, convection and radiation in heat transfer. 3D CFD simulation is used for this calculation. 3D CFD simulation was performed to predict the peak cladding temperature of a spent fuel assembly. The maximum temperature of 3D simulation is lower than that of 2D. This result would come from the difference of heat transfer modes used for simulation. The axial length of the assembly modeling would be not enough to study the trend of the temperature.

[en] A two-dimensional immiscible droplet deformation phenomenon on a moving channel bottom wall is simulated using the lattice Boltzmann method. We considered the effect of the initial static contact angle, the capillary number, and the size of the droplet on the dynamic behavior of the moving droplet. When the initial static contact angle is less than 90 .deg. , the moving droplet is deformed and stretched, resulting in increasing width and decreasing height of the droplet. This is due to the hydrophilic (wetting) characteristic of the channel's bottom wall. However, when the initial static contact angle is larger than 90 .deg., the deformed and stretched droplet on the moving channel bottom wall is broken up, and is then pinched off or detached from the moving channel bottom wall, depending on the initial static contact angle and capillary number. This is due to the hydrophobic (non-wetting) characteristic of the wall.

[en] We investigated the flow and heat transfer characteristics in a Twisted elliptic tube (TET). The effects of geometry parameters such as the aspect ratio and number of rotations in the TET were analyzed comparatively using three-dimensional (3-D) numerical simulation. We also solved numerically the conservation equations of continuity, momentum, and energy in the TET. Fully developed flow in the TET was modeled using the realizable k-ε turbulence model and steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations. The simulation was performed for Reynolds numbers of 100, 1000 and 10000. The pressure drop and the heat transfer of the TET were assessed in terms of the Darcy friction factor and Colburn j-factor, and overall performance was evaluated using the area and volume goodness factors