Simulation And Experimental Research On The Flow And Heat Transfer Performance Of Micro-needle Ribs With Different Shapes

The global energy shortage and the development trend of high power,high integration,and high heat flux density of electronic components make the cooling technology of MEMS face severe challenges,which seriously affects the normal operation of electronic equipment.Laying micro pin-fin arrays in the microchannels to strengthen the heat transfer structure can effectively increase the heat transfer area and enable efficient heat transfer when the fluid crosses the micro pin-fins,but at the same time,the flow resistance will increase.Based on the factors that affect the heat dissipation performance of heat sinks,the paper studies the flow heat transfer performance of micro pin-fin arrays with different shapes.Firstly,In this paper,deionized water was used as the working medium,and the single-phase flow and heat transfer characteristics of differently shaped pin-fin microchannels under steady-state laminar flow were experimentally studied.The research shows that the influence of heating power on the frictional resistance coefficient is small,and the frictional resistance coefficient of the circular pin-fin array decreases with the increase of Reynolds number at different powers.The pressure drop in the micro pin-fin arrays increased with the increase of Reynolds number,the pressure drop of the triangular pin-fin was the largest,and the ellipse was the lowest.The average surface temperature of the bottom plate decreases with the increase of the Reynolds number,the temperature of the triangular pin-fin bottom plate is the lowest,and the drop shape and the ellipse pin-fins are the highest.Both the convective heat transfer coefficient and the Nusselt number increase as the Reynolds number increases,and the triangular pin-fin has the largest heat transfer coefficient.The shape of the pin-fin affects the flow and heat transfer characteristics of the microchannel.The effect is small at a small Reynolds number and significant at a large Reynolds number.Secondly,a numerical simulation of single-phase flow and heat transfer across the micro pin-fin arrays of the working fluid was carried out.The study found that the velocity of fluid was the smallest near the fin-fins and the channel wall,and the velocity between the channel wall and the pin-fins was the highest.The leading edge of the pin-fins has a high pressure,and there is a local low pressure zone in the headstream and tail flow zone.With the increase of Re,irregular vortices and disturbances are generated at the tail of the pin-fins.The triangular pin-fin array has the most severe turbulence,the largest pressure drop and frictional resistance coefficient.The working fluid at the tail of the drop shape and ellipse pin-fins has less disturbance and less pressure.Thirdly,the formation of the tail vortex in the micro pin-fin arrays was studied,and the effect of vortex on fluid convection and heat transfer was analyzed.At low Reynolds numbers,no backflow occurs at the tails of the pin-fins of all shapes.At high Reynolds numbers,vortices begin to appear at the tails of pin-fins.Reflow occurred first at the tails of the triangular and circular pin-fins,and secondly at the diamond pin-fin.Within the range of the Reynolds number studied,the flow of the ellipse and drop shape pin-fins remained stable,and no vortex was observed.The vortex at the tail of the pin-fin has a certain effect on the heat transfer performance of the fluid.Compared to ellipse,drop shape and diamond,the flow disturbance in the circular and triangular micro pin-fin arrays is more severe,the area of the tail vortex is larger,the pressure drop and the area of the high-temperature region at the tail is also larger.Finally,the enhanced heat transfer factor ? was used to analyze the flow and heat transfer performance of the micro pin-fin arrays,and the correlations between f,Nu and ?and Reynolds number were obtained by fitting.The enhanced heat transfer factor ?increases with the increase of Reynolds number,the triangular pin-fin has the largest enhanced heat transfer factor and the best enhanced heat transfer effect.Due to the different processing methods,processing materials,experimental conditions of micro pin-fin arrays,and the complexity of flow at the microscale,the existing correlation prediction values still differ from the experimental results of pin-fin arrays.