De-ionized water

used as working fluid

flows through a staggered micro-cylinders-group

which is made up of micro-cylinders with hydraulic diameter of 500 μm and height of 500 μm

and an experimental study is performed on the influence of tip clearance on heat transfer efficiency in the staggered micro-cylinders-group.Using an electricity heater

the flow rate and the temperature difference between the inlet and the outlet of micro-cylinders-group are measured and the friction factor and Nusselt numbers can be obtained over Reynolds numbers ranging from 8 to 400.The relationship between heat transfer efficiency and Reynolds number is grasped.The experimental results indicate that the tip clearance has a little influence on flow resistance and Nusselt number at low Reynolds number and these influences become apparent with the increase of Reynolds number.The heat transfer efficiency of micro-cylinders-group heat sink increases rapidly with Reynolds number for a start

and it increases slowly with the increase of Reynolds number

even begins to drop with the further increase of Reynolds number.However

the existence of the tip clearance promotes heat transfer efficiency in the micro-cylinders-group heat sink

though it reduces Nusselt number based on the experimental results.