A non-destructive model for thermal-hydraulics of wire-wrapped rod bundle and wire-rod contact corner microscopic behavior

Abstract

Wire-wrapped rod bundle numerical simulation relates to multiscale parameters, such as axial length of the rod bundle (600 mm) and wire-rod contact corner (0.4 mm). The existing studies tend to adopt the embedding approximation wire model, which cannot simulate microscopic behavior at the wire-rod contact corner and bring the uncertainty of numerical models. To simulate the actual situation of the wire-wrapped rod bundle, this paper established a high-precision non-destructive wrapped wire model based on virtual ellipse flow surfaces and fillet connection and then investigated the thermal-hydraulics of the wire-wrapped rod bundle and microscopic behavior at wire-rod contact corner at the working pressure of 25 MPa, inlet temperature of 692.45 K, mass flux of 1000 kg/m2·s, and heat flux of 400 kW/m2. The influence of the distance of wire embedded into the rod bundle on heat transfer and pressure drop was quantitatively analyzed. ω-RSM turbulence model is used due to its higher prediction accuracy in the high enthalpy region (enthalpy >2700 kJ/kg). The result shows that numerical simulation has a good agreement with the experimental data. Compared with embedding approximation models, the high-fidelity non-destructive wrapped wire model shows better heat transfer and greater friction resistance. The wire-wrapped rod bundle increased the heat transfer coefficient by 14% and increased the friction factor by 10% compared with the bare rod bundle. A dead-water area exists at the wire-rod contact corner with the phenomena of low velocity, poor heat transfer and high fluid temperature. This numerical investigation helps to optimize the wire structure design while providing insight into the influence of wire.