Three drop-shaped micro pin-fin heat sinks with different tail angles were designed based on the optimization of traditional round micro pin-fin heat sink.The flow resistance and heat transfer characteristics of the heat sinks were experimentally investigated using deionized water as working fluid.The results show that the micro pin-fin with tail angle of 60° has the lowest flow resistance among the heat sinks.The streamlined structure of drop-shaped micro pin-fins improves the distribution of flow and delays the conversion from laminar to turbulent flow.The smaller the angle

the more obvious the effect.The optimal angle of drop-shaped micro pin-fin is different under different flow rates.The heat sink with tail angle of 60° has the strongest heat transfer coefficient at the corresponding Reynolds number in this experiment (Reynolds number is equal to 200-1000).When the tail angle decreases to 30°

the heat transfer is also enhanced in the tail section of micro pin-fin.However

the flow is affected by the micro pin-fin behind

so the heat resistance is higher than other heat sinks under the same pump power.