Convective Heat Transfer within Spent Fuel Canisters: An Experimental Laboratory Study

摘要

Heat transfer correlations are developed for a vertical annulus wherein the inner cylinder is electrically heated at a rate scaled tothat expected in a typical pressurized or boiling water reactor subassembly. The outer cylinder is maintained at a constant temperature and provisions have been made in the design of the apparatus for future experiments with multiple rod arrays having a specific power genation similarily scaled to that in a fuel rod subassembly. Overall heat transfer data are corrected for thermal radiation in the annulus; and Rayleigh numbers, based on the gap width, span the conduction, transitio and turbulent regimes of free convection. A total heat transfer coefficient is also obtained for each run via lineraization of the radiative transport across the annulus. Heat transfer coefficients are obtained with air and helium as the fill media. The range or Rayleigh numbers for the present data is 300 < Ra < 2.3 x 10 exp 6 . Generally, the energy transferred by radiation across the annulus, as a fraction of total heat transfer, varies with Rayleigh number and fill medium. With air as the fill medium, thermal radiation can account for more than 40% of the heat transfer. With helium, radiation can account for up to one-third of the heat transfer rate. The results of the present work establish a baseline of comparison of het transfer coefficients to be obtained with a multiple rod array and for the assessment of the effects of thermal radiation on heat transfer in a fuel rod bundle.