Benchmark of Natural Convection/Radiation Simulations Within an Enclosed Array of Horizontal Heated Rods

Experiments performed by Lovett (1991) measured the temperature of an 8 × 8 array of horizontal heated rods in air within a constant temperature enclosure. That apparatus was a scaled-down model of a spent boiling water reactor fuel assembly in a transport package. In the current work, three-dimensional computational fluid dynamics simulations of natural convection and radiation heat transfer within this domain were conducted to determine appropriate boundary conditions and benchmark the results. Initial simulations employed nearly equal specified temperatures on the walls and endplates, and insulated rod ends. They accurately reproduced the shapes of the temperature profiles in the midplane but overpredicted the temperature level at the highest heat load. Simulations that included conduction within the endplates and convection from their outside surfaces more accurately modeled heat losses and brought the midplane temperatures close to the measured data. These experiences will be used to design experiments to benchmark simulations of spent fuel assemblies in transport package support structures.