Temperature measurement of a heated rod array within a square cross section enclosure filled with dry rarefied helium

Abstract

The goal of this work is to obtain experimental data that can be used to validate computational models that quantify the effect of gas rarefaction on heat transfer during vacuum drying of used nuclear fuel transport/storage canisters. An experimental apparatus is constructed, consisting of a 7 × 7 array of electrically heated rods held by spacer plates near their ends and contained within a square cross-section helium-filled pressure vessel. Thermocouples are used to measure heater rod, spacer plate, and enclosure temperatures for a range of rod heat generation rates, helium pressures in the continuum and rarefied-gas slip regimes, and different thicknesses of insulation outside the enclosure, which increases the apparatus temperatures. The results shows that the temperature difference between the enclosure and the rods increases by less than 4% when the pressure decreases within the continuum regime (from ~ 105 to 5700 Pa). However, it increases by up to 78% in the slip regime (~5700 to 65 Pa), due to the temperature-jump thermal resistance at the gas/solid interfaces. Random variation in the measured temperatures, caused by configuration and measurement errors, is less than 1.1℃, which makes this data well suited for benchmarking computational methods for calculating heat transfer and temperatures in used nuclear fuel canisters under vacuum drying conditions.