Effect of circular cylinder diameter on heat transfer enhancemant of wall
(1. School of Automotive and Traffic Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. School of Mechanical Engineering, Nantong University, Nantong, Jiangsu 226019, China)
Abstract：To investigate the effect of inserting cylinder with different diameters near the wall on the heat transfer enhancement of wall in transition flow, a numerical calculation method was used based on a composite grid system. When Reynolds number of Re was 200 with cylinder diameter of D from 5 mm to 14 mm, the numerical calculations for the flow around cylinder near the wall were carried out. The lowwatervelocity flume test rig was used to verify the numerical calculation method. The results show that the inserting cylinder near the wall can bring the flow into transition flow state in advance, which is beneficial to heat transfer. For the same gap ratio of C/D with C meaning the distance between the cylinder and the lower wall, changing D just affects the size and location of the second peak. With the increasing of D, the size and strength of the periodic shedding vortex and nearwall vortex in the wake of cylinder are increased, and the occurrence location gradually moves downstream. As D is increased within the transition flow range, the heat transfer enhancement on the downstream wall is increased with increased action area. Under different D, the optimal insertion position of C for the second peak of the curve reaching the maximum remains basically unchanged. With the increasing of D, the optimal gap ratio of C/D is decreased.
