Study On Flow And Heat Transfer Characteristics In Ring-shaped Micro Pin Fin Arrays

In recent years,electronic components are developing towards miniaturization,integration,and high power.Efficient heat dissipation has become a significant challenge for their development.Micro-pin-fin heat exchanger,featured by its large surface-tovolume ratio,good temperature uniformity and high heat transfer rate,has become an efficient solution to break through the heat dissipation bottleneck of highly integrated electronic components.Therefore,it has become a research hotspot worldwide.This study proposes a modified micro-pin-fin array with a non-closed 3/4 ringshaped cross section.Firstly,the Micro-PIV flow field visualization experimental system and the convective heat transfer experimental system is established.Effects of pin fin cross section shape and layout on flow and heat transfer characteristics of the novel micropin-fin array is investigated experimentally,with the circular micro-pin-fin array of the same size as a reference.Relationship between streamline distribution,velocity distribution,pressure drop,friction factor,convective heat transfer coefficient,Nusselt number(Nu)and Reynolds number(Re)is analyzed.The result shows that the crosssectional shape of the micro-pin-fin has a significant effect on the location of the vortex center,vortex width and vortex length.Under the same working conditions,the symmetrical vortex appears earlier in the ring-shaped micro-pin-fin array,and the flow velocity in the mainstream is higher than that in the circular micro-pin-fin array.The pressure drop between the inlet and outlet of the four microchannels increases with the increase of Re,while the friction factor decreases with the increase of Re.The friction factor in the ring-shaped micro-pin-fin array is smaller than that in the circular micro-pinfin array.Under the same experimental conditions,the effect of pin fin layout on the convective heat transfer coefficient and Nusselt number is smaller than the cross-sectional shape.The single-phase convective heat transfer coefficient and Nusselt number in the ring-shaped micro-pin-fin array are greater than that in the circular micro-pin-fin array.Secondly,numerical simulation is conducted to study the effects of cross-sectional shape,layout and height of the micro-pin-fins on the single-phase flow and heat transfer performance,and the simulation results are in good agreement with the experimental results.The results show that the vorticity intensity and the area of positive and negative vorticity in the ring-shaped micro-pin-fin array are larger than that in the circular micropin-fin array.The temperature of the fluid in the channel increases gradually along the flow direction.The single-phase convective heat transfer coefficient and Nusselt number in the staggered micro-pin-fin arrays are greater than that of the in-line micro-pin-fin arrays.The single-phase convective heat transfer coefficient and Nusselt number in the ring-shaped micro-pin-fin arrays are greater than that in the circular micro-pin-fin arrays.The effect of the fin height on heat transfer performance is greater than that of the crosssectional shape.The convective heat transfer coefficient in the ring-shaped micro-pin-fin arrays increases with the increase of the fin height.Finally,the thermal-hydraulic performance factor(TPF)was introduced to comprehensively evaluate the overall heat transfer performance of different micro-fin array channels,and it is found that the TPF in the ring-shaped micro-pin-fin arrays is always higher than that in the circular micro-pin-fin arrays.Compared with circular micro-pin-fin arrays with the same arrangement,the ring-shaped micro-pin-fin array can improve the overall heat transfer performance of the channel by more than 32.29%.In the scope of this study,the TPF in the channel first increases and then decreases with the increase of the fin height.When considering the influence of pressure drop and heat transfer coefficient on the micro-pin-fin arrays comprehensively,the staggered ringshaped micro-pin-fin arrays channel with fin height of 0.5 mm has the best comprehensive heat transfer performance.