Numerical Study On The Flow And Heat Transfer Characteristics Of Microchannel Heat Sinks

In this dissertation,the heat transfer problems of high density,small volume and high integration electronics have been investigated.Numerical simulations are carried out to study the influence of geometric parameters on the flow and heat transfer characteristics.And then one parameter is varied while others are kept constant,the influence of aspect ratio of rectangular microchannel,microchanel with different shape,different materials on the flow and heat transfer characteristics were analyzed.And finally we investigate two kinds of novel micro channel heat sink,and analyzed the effect of double layered microchannel and microchannel with micro wedge on improving the performance of heat sink.A good agreement is found between numerical results and experimental data when the variation of water viscosity with temperature is taken into account.The microchannels with high aspect ratio,long wetted perimeter and small hydraulic diameters usually have low thermal resistance and high pressure drop.For the rectangular microchannel,it has the best performance with the aspect ratio among 8.904-11.442.Then,the flow and heat transfer characteristics of rectangular,trapezoidal and triangular shaped microchannel heat sinks are compared.Under the same cross section area and hydrodynamic diameter,rectangular microchannel owns the best heat transfer coefficient,followed by trapezoidal microchannel heat sink,and the heat transfer coefficient of triangular microchannel is worst.Meanwhile,the channel number also affects the thermal resistance and pressure drop.we analyzed influence of channel number of microchannel heat sink on the heat sink performance,we found that the increase of channel number reduces the thermal resistance,but at the expense of high pressure drop.Under the condition of the same power consumption,the channel number has an optimum range.The flow and heat transfer characteristics of micro channel heat sink with different materials are also investigated.With other conditions are unchanged,the thermal resistance of copper based microchannel heat sink is lowest,and steel made heat sink have both the worst heat transfer coefficient and highest pressure drop.The flow and heat transfer characteristics of aluminum based heat sink are both superior than silicon based microchannel heat sink.Finally,we investigate two kinds of novel micro channel heat sink,and analyzed the effect of double layered microchannel and microchannel with micro wedge on improving the performance of heat sink.By comparison with conventional single layer microchannel heat sink,we find that the temperature field of microchannel with micro wedge is the most uniform,which has the best heat transfer coefficient.