Numerical simulation of turbulent air flow on a single isolated finned tube module with periodic boundary conditions

A helically segmented finned tube bank is simulated as a single isolated finned tube module in order to reduce computational domain in 99%. The numerical simulation is conducted with the Reynolds Averaged Navier-Stokes Equations (RANS) approach and the turbulence effect is modeled with the k-ε RNG model. The finned tube geometry is represented by means of cut-cell method, whereas the inside fluid temperature is considered by means of an average temperature. Periodic boundary conditions are implemented and, as a consequence, new terms in momentum and energy equations should be included to represent pressure drop and cooling air flow. Results show the effect of implementing periodic boundary conditions on turbulent kinetic energy, and its dissipation rate only is reflected on local properties in the zones of high flow interaction. Predictions are validated with experimental data and the best correlations available in the open literature. Results show good precision and the same tendency in the velocity field. The numerical-mean friction factor and Nusselt number present deviations of 0.67% and 2.98%, respectively. Therefore, an appropriate representation of turbulent flows is obtained and the numerical model can be applied to studies on heat exchangers at industrial scale.