Koji Toriyama

Reverse Flow on Three-dimensional Mixed Convection in a Horizontal Square Duct (In Case of Three Heated and Cooled Walls of the Duct)

Effects of the reverse flow on heat transfer and flows in a horizontal square duct were examined numerically and experimentally for various inlet fluid temperatures. The working fluid was water. This analysis was performed in two cases. In the first case, wall temperature (Tω=60°C) was higher than the inlet temperatures (T0=10-50°C). In the second case, wall temperature (Tω=5°C) was lower than the inlet temperatures (T0=10-40°C). In the numerical analysis, the SIMPLE procedure and QUICK scheme were used to solve the governing equations through a control volume. The temperature dependence of kinetic viscosity and thermal conductivity of water was considered. In the experiment, the flow was visualized by a dye injection method. Results present that a reverse flow appears on the upper wall in the first case and on the other hand it does on the bottom wall in the second case. The size of the flow reversal increases linearly with the product of the Richardson number Ri (=Gγ/Re2) and Prandtl number Pγ (=ν/a). The heat transfer behavior was discussed corresponding to the flow.