Experimental determination of heat transfer and fluid flow over drift-emplaced canisters

Drift-emplaced waste canisters are under consideration for the long-term storage of high level spent fuel in the proposed underground repository at Yucca Mountain. These canisters will be placed on pedestals above the floor of the drifts and exchange heat with the walls of the drift and with air circulating through the repository. To assess the requirements of the repository ventilation system, values of the dimensionless convective heat transfer coefficient and the pressure drop across individual canisters were measured in an experimental model of the drift. The results were curve-fitted as functions of the spacing between the canisters and the Reynolds number of the flow. Both natural and forced convection effects were investigated. Pressure drop data was acquired for a range of Reynolds numbers. The spacing between canisters was varied and the data was valid for d/D = 0.25, l/d = 7.33 and for 4,000 {dollar}\u3c{dollar} Re {dollar}\u3c{dollar} 30,000. The loss coefficient decreased as the spacing between canisters decreased. This was likely due to the limited space available for wake formation in the closure spacing and the subsequent loss in wake drag. From the analysis of Nusselt number data for forced convection, it was observed that the canister spacing had very little effect on the convective heat transfer; From the analysis of Nusselt number data for natural convection, it was observed that the Nusselt number decreased as the spacing increased. The data was valid for 150,000 {dollar}\u3c{dollar} GrPr {dollar}\u3c{dollar} 220,000. The results show that the heat transfer rates for natural convection from canisters in a cylindrical drift exceeded the case of long cylinders with no enclosures by 12% to 50%