关键词: 凹坑;涡流;换热系数;红外热像仪;瞬态测量

Abstract: To reveal the mechanism of heat transfer enhancement with dimpled wall,local heat transfer coefficient distributions on a wall with a single spheric dimple were experimentally investigated in a rectangular channel.The heat transfer rate on a smooth wall was also measured for comparison.A transient heat transfer method was used by assuming a one-dimensional semi-infinite conduction model during the experiment.Step rising of the mainstream temperature was accomplished by using a fast-response metallic-net heater,and the transient temperature distributions on the test surface were measured with an infrared thermography.Surface flow visualization on the dimpled wall was made using oil and powder.Reynolds numbers ranges from 1.58×104 to 6.36×104.It was observed that the heat transfer rate on a dimpled wall has a close relationship to the vortex structure created by dimple.Vortex induced by a single spheric dimple can increase the heat transfer rate for a maximum of 80% at the downstream edge of the dimple.Averaged level of 20%～30% heat transfer enhancement was achieved in the area of dimple wake.

Key words: Dimple;Vortex;Heat transfer coefficient;Infrared thermography;Transient measurement