Heat Transfer of Three-Dimensional Backward-Facing Step Flow: Local Heat Transfer Coefficients on the Bottom Wall and Upper Wall

摘要

The heat transfer mechanism especially three-dimensional characteristics based on backward-facing step (BFS) flow mounted in a duct under relative low Reynolds number region have not yet clearly clarified by experimental measurement. Thermo-sensitive liquid crystal method was made use of for obtaining the local heat transfer distributions on the bottom wall and upper wall to investigate the local heat transfer deterioration and enhancement area and check the existence of three-dimensionality. MLP (Multilayer Perceptron) method was adopted for building the relationship between the RGB value of thermo-sensitive liquid crystal sheets and wall temperature value. Large attention was paid to the average and maximum Nusselt number on the bottom wall and upper wall. The average Nusselt number value over the entire bottom wall and the upper wall can be estimated by the average Nusselt number at the center of the flow channel. Obvious heat transfer three-dimensionality was found both on the bottom wall and upper wall in low Reynolds number range.