Heat transfer characteristics of baffled channel flow

Heat transfer characteristics of baffled channel flow, where thin baffles are mounted on both channel walls periodically in the direction of the main flow, have been numerically investigated in a laminar range. The main objectives of the present study are to find the physical reason responsible for the heat transfer enhancement in finned heat exchangers, and to identify the optimal configurations of the baffles to achieve the most efficient heat removal from the channel walls. Two key parameters are considered, namely ratio of baffle interval to channel height (R_B) and Reynolds number (Re). We performed a parametric study and found that the large-scale vortices travelling along the channel walls between the neighboring baffles, which are generated by flow separation at the tips of the baffles and become unsteady due to a Hopf bifurcation from steady to a time-periodic flow, play the key role in the heat transfer enhancement by inducing strong vertical velocity fluctuation in the vicinity of the channel walls. We also propose a contour diagram (map) of averaged Nusselt number on the channel walls as a function of the two parameters. The results shed light on understanding and controlling heat transfer mechanism in a finned heat exchanger, being quite beneficial to its design.