압전세라믹 냉각팬 시스템용 히트싱크 형상에 대한 연구

Abstract

In order to enhance the convection heat transfer performance of piezoelectric fan for cooling of electronic devices, this study presents a new type of heat sink for the piezoelectric fan system. Piezoelectric fan generates much better cooling performance than natural convection with minimal power consumption and small dimension and it can be applied to small electronic devices such as mobile or small chips. Piezoelectric fan differ from conventional rotational fan system by its unique flow type. That flow is induced by amplified vibration of piezoelectric material and act like very fast hand flap. And the flow consisted by two type of flows. The jet flow from in front of piezoelectric fan is much faster and used main cooling method and the rotating eddy flows around piezoelectric fan are the most volume of piezoelectric fan induced flow. But this eddy flows are diffuse to outer air and usually unutilized. And most of implementation of piezoelectric cooling system that combination of piezoelectric fan with heat source of certain geometries (heat source surface) has plain surface. That means many piezoelectric fan systems are on the simple surface and small heat transfer area. Therefore, piezoelectric fan’s performance is limited by its small heat transfer area. This study suggests new type of heat sink geometry for the piezoelectric fan system that can widen the heat surface and flow velocity with simple geometrical improvement. And this research aided by numerical method that improve research efficiency and verified by experimental manner. The general CFD code of FLUENT™ and its Dynamic Mesh Modeling (DDM) capability is applied to describe the deforming of boundary wall that regarded as cantilevered piezoelectric fan. DDM is utilized by FLUENT™ User Defined Function and it describes simple 2nd-order of deforming equation of boundary wall for the time variable and magnitude of x coordinate. The final ‘Improved’ design of new heat sink for piezoelectric fan shows 39.3% of improvement of cooling performance than conventional systems in the 8000 of heat flux and 26.9% of improvement in the 13,333 of heat flux.