Axisymmetric Jet Impingement onto a Heated Cylinder

Abstract

The prediction of the flows and temperatures in the moderator system of CANDU reactors is important in the safety evaluation during some potential transients. An experimental program to collect data for CFD validation, including integrated moderator circulation tests has been funded by the CANDU Owners Group. This thesis constitutes a separate effect test within this larger moderator flow study, investigating the behaviour of a jet impinging onto a single heated cylinder. A number of experiments were conducted to investigate the behaviour of the jet flow under a variety of scenarios. The inlet Reynolds number and the heater power level were the primary variables considered to assess the impact of the buoyant forces generated by the heated cylinder on the flow. Alongside the experiments, simulations were performed using the experimental geometry to evaluate the performance of some of the most commonly-used turbulence modelling approaches – namely the standard k-ε, realizable k-ε, and standard k-ω RANS models. The agreement between the turbulence models and experimental results was determined to be reasonable in the free jet regions, however nearer the cylinder, the simulated results exhibited a wider core region and steeper gradient in the shear layer than the experimental data. At lower Reynolds numbers, over-prediction of velocities both in the axial and lateral direction was also seen. The impact of heating proved minimal in the jet core, however differences were observed in the shear layer at lower Reynolds numbers, and the heated case exhibiting decreased lateral velocities as compared to the isothermal case.