Numerical Study On Heat Transfer Enhancement Of Air-cooling Heat Sinks For Electronic Devices

As power density of electronic devices increases rapidly,a better performance of heat dissipation is urgently required.Forced air convection is the most common cooling technique to maintain electronic devices in normal temperature range,hence three typical air-cooled heat sinks,plate-fin heat sinks,rectangular channel filled with metal foam and plate-fin radial heat sinks,are selected to enhance the heat dissipation performance,in order to provide the ways for the heat transfer enhancement of electronic cooling devices.The flow and heat transfer performance of heat sinks was numerically studied and analyzed by CFD software.Firstly,the traditional parallel plate fin CPU heatsinks with two inlet has poor performance because of the low-speed zone at the bottom center.The influence of baffle heights on the cooling performance of parallel plate fin heatsinks was compared,by adding baffles on the upper part of inlet.It is found that the partially closed air inlet can increase the air velocity in the low speed area and reduce the maximum temperature of the heat sinks.Under the conditions of low air velocity and high heat flux,adding baffles can improve the cooling effect most significantly.Also the heat sinks with gradient porous material(GPM)are numerically investigated.The effects of graded porosity on the overall Nusselt number,pressure drop and heat transfer coefficient are examined.The result shows that heat sinks with GPM in the z direction has a lower pressure drop.Moreover,the configuration with the porosity decreasing from 0.963 to 0.7 in the z direction can achieve a better performance than HPM(homogeneous porosity material)heat sinks with a porosity of 0.832.Finally,the structural optimization of the traditional plate-fin redial heat sinks is was conducted based on the total thermal resistance.A numerical model of two novel structures sinusoidal corrugated fin and plate fin with cylindrical convex are proposed.The effects of geometric parameters,such as the sinusoidal function amplitude,period and the number arrangement and radius of bugles on heat resistance,are thoroughly considered.The result of this study shows that the sinusoidal function amplitude and period have little influence on heat transfer performance.The total thermal resistance decreases with the increase of the number of protrusions,and the best protrusion arrangement is front sparse and back dense.In addition,the non-uniformity of bulges size can affect the heat transfer performance of plate fin redial heat sinks.