HYDRA-2, 3-D Heat Transport for Spent Fuel Storage System

1 - Description of program or function: HYDRA2 is a hydrothermal computer code capable of three-dimensional analysis of coupled conduction, convection, and thermal radiation problems. HYDRA2 is especially appropriate for simulating the steady-state performance of spent fuel storage systems. Several automated methods are available to model radiation transfer within enclosures and from fuel rod to fuel rod. HYDRA2 provides a finite-difference solution in Cartesian coordinates to the governing equations of mass, momentum and energy. A cylindrical coordinate system may also be used to enclose the Cartesian coordinate system. This exterior coordinate system is useful for modeling cylindrical cask bodies. The difference equations for conservation of momentum incorporate directional porosities and permeabilities that are available to model solid structures whose dimensions may be smaller than the computational mesh. The equation for conservation of energy permits modeling of orthotropic physical properties and film resistances. When both coordinate systems are invoked, the code will automatically align the two systems and enforce conservation of energy at their interface. 2 - Method of solution: An implicit solution algorithm is used for both the momentum and energy equations to ease time-step limitations and stability requirements. The time-dependent conservation equation of energy with convection and heat sources is the basis for calculating temperature fields. A control-volume formulation is used to derive the algebraic equations from the basic differential equations. 3 - Restrictions on the complexity of the problem: HYDRA2 does not provide a turbulence model to represent sub-grid scale motion of the fluid. Therefore, the Reynolds/Rayleigh numbers realized in the simulation must be sufficiently low so that all the scales of motion are resolved by the computational grid. Other limitations include no mass inflow/outflow boundary conditions and planar or two-dimensional cavity radiation heat transfer