Investigation of Heat Transfer and Turbulence Characteristics of a Triangular Rod Array in lattice-Boltzmann Framework – A. Tiftikci, C. Kocar

In present study, triangular subchannel of VVER-440 reactor is simulated using with lattice-Boltzmann and finite volume methods. The heat transfer and flow characteristics such as pressure drop, heat transfer coefficient, temperature and velocity distributions are obtained by using both LBM and FVM. The selected VVER subchannel has pitch-to-diameter ratio of 1.35. Simulations are carried out in two stages: bare rod bundle and rod bundle with spacer grid simulations. The FVM calculations are handled using ANSYS Fluent 15.0 CFD Solver. Smagorinsky (LES) turbulence model and heat transfer modules are implemented to the lattice-Boltzmann framework. The heat transfer module works in conjunction with the turbulent flow computations. For both LBM and FVM, turbulence model study was accomplished and the post-processed turbulence quantities, velocity and temperature profiles, heat transfer coefficient and pressure drop values are compared with experimental data and correlations. The comparisons show that lattice-Boltzmann simulations are in good agreement with the finite volume method based LES simulations and also used experimental data. After completing the validation process of lattice-Boltzmann code, the spacer grid effect on heat transfer characteristics and flow dynamics are then investigated.