Influence of tip clearance on heat transfer efficiency in micro-cylinders-group heat sink

De-ionized water, used as working fluid, flows through the in-line and staggered array micro-cylinders-group heat sinks with different tip clearances, which are made up of micro-cylinders with hydraulic diameters of 0.5 mm and heights of 0.5 mm. The resistance characteristic and the Nusselt numbers in micro-cylinders-group heat sinks at in-line array and staggered array can be experimentally obtained over Reynolds number ranging from 8 to 400, so the heat transfer efficiency in the micro-cylinders-group heat sink is given. The investigations show that the tip clearance has a little influence on flow resistance and Nu of micro-cylinders-groups heat sink at low Re and this influence becomes more apparent with the increase of Re. The heat transfer efficiency of micro-cylinders-group heat sink increases rapidly with Re at first, and then becomes slowly, even begins to drop with the further increase of Re. However, the existence of the tip clearance promotes the heat transfer efficiency in micro-cylinders-group heat sink in the present study.

► Surface temperature distribution is obtained by IR camera with a magnifying lens.
► We give detailed explanations for some abnormal phenomena about this test.
► The existence of tip clearance obviously drops flow resistance and Nusselt number.
► The existence of tip clearance promotes heat transfer efficiency in test section.