On numerical simulations of flow and heat transfer of the bend part of a U-duct

Two-dimensional numerical simulations of the flow and temperature fields inside the bend (turn) part of a U duct have been performed. Both the standard and low Reynolds number k-epsilon models were used to solve the smooth bend (turn) part and ribbed bend (turn) part, respectively. For the standard k-epsilon model, the wall function approach was used at the near wall region where the log-law was assumed to be valid, whereas the modelling damping functions were used in the low Reynolds number model. In the case of the ribbed bend (turn) part, two approaches were used, the total approach and an approach based on periodic flow condition. The details of the duct geometry were as follows: the cross section area of the straight part is 50x50 mm(2), the inside length of the bend part 240 mm, the cross section area of the rib is 5x5 mm(2) and the rib height-to-hydraulic diameter ratio, e/Dh, is 0.1. The results are compared with experimental data obtained for the same conditions.