The curvature and bending direction of a sinusoidal channel show periodic changes, so its internal flow and heat transfer characteristics are more complex. In this paper, Direct Numerical Simulation method is used to calculate the square sinusoidal channels with different cross-sectional ratios. The results show that in the laminar flow range, the Dean vortex loses stability when the Reynolds number increases to a certain value, which is manifested as random fluctuations of the Dean vortex with time and space. This state is called Dean instability phenomenon, and the critical Reynolds number corresponding to 1:2 cross-sectional ratio of the sinusoidal channel is determined by using the helicity discrimination method. In addition, by comparing the heat transfer characteristics of the channels in the two states, it is found that after reaching the Dean instability state, the heat transfer enhancement caused by the Dean vortex is not limited to a fixed position, which has significant implications for enhancing the heat transfer capacity and reducing the wall temperature difference.
Keywords Heat exchanger, Dean instability phenomenon, Critical Reynolds number, Heat transfer characteristics