Implementation and experimental validation of a computational model to predict temperatures and heat transfer of a square array of heated rods enclosed in a pressure vessel filled with rarefied dry helium

Abstract

A temperature-jump thermal resistance, based on results from Lin & Willis 1979, was implemented at the gas/solid interfaces of a three-dimensional computational fluid dynamics model of a 7 × 7 array of heated rods within a square-cross-section pressure vessel filled with rarefied dry helium. This configuration is relevant to the vacuum drying of used nuclear fuel canisters. Simulations were performed for a range of rod heat generation rates, boundary temperatures, and gas pressures in the continuum and rarefied-gas-slip regimes. Experiments conducted by the current authors were used to measure rod and enclosure temperatures for the same conditions, to validate the simulations. For all measurement locations and experiments, the measured rod-to-boundary temperature differences varied from 12 °C to 102 °C. The simulated differences correlated linearly to the measured differences, closely following variations for different locations and experiments, but exhibited random variations from the best-fit line. In the slip regime, the predicted rod-to-boundary temperature differences were systematically 0.9 °C smaller than the measured values (less than half of the thermocouple uncertainty), and 95% of the simulated differences were less than 2.5 °C from the best-fit line (14% larger than the rod thermocouple uncertainty). The temperature-jump thermal resistance model will be useful for predicting temperatures during vacuum drying operations.