Transient Heat Transfer Characteristics of Round Jet Impacting on Inclined Concave Cylindrical Surface Based on Thermochromic Liquid Crystal

摘要

The transient heat transfer characteristics of a single circular hole jet impacting concave cylinder were obtained by thermochromic liquid crystal. In the study, the airflow Reynolds number Re, the impact distance to nozzle diameter ratio L/d and the jet impact angle α were changed. The color change process of the concave surface of the experimental part was photographed by the industrial camera. The local Nusselt number Nu_D distribution was calculated. The results show that the distribution of Nu_D for the initial phase of the jet impingement is bell type in a radial direction along the impact center. And with the impact process, the Nusselt number at the stagnation point Nu_s decreases gradually, where the maximum difference is 26.9%. When Re increases and L/d close to 4, the second peak is gradually obvious. As α increases, the second peak moves to the region of r / d ≤ 0 gradually. In addition, the linear relationship between the Re, L/d, a and Nu_s is obtained by linear analysis.