The concept of periodic renewal of boundary layers is a promising technique for the enhancement of heat transfer in microchannels. Extending the above concept, microchannel heatsink with modified hexagonal fins has been proposed for disrupting the flow periodically. An experimental study has been carried out to investigate the heat transfer and fluid flow characteristics of a microchannel heat sink with modified hexagonal fins and a conventional type of microchannels with plate fins. The heat transfer and fluid flow characteristics of the modified hexagonal fin microchannels have been compared with the plate fin microchannels. The heat transfer enhancement factor and pressure drop penalty factors are evaluated and compared. The modified hexagonal fin microchannel heat sink has been found to outperform the plate fin microchannel heat sinks in spite of the lesser heat transfer area.

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Cooling of miniature size electronic components has become a challenge for designer in the development of integrated circuits. Micro pin fin heat sink and Micro channel pin fin heat sink are thermal management techniques for effective cooling. The paper presents comparison of fluid flow and heat transfer characteristics for micro pin fin heat sink and micro channel pin fin heat sink with unfinned micro channel heat sink. A three-dimensional heat sink with water as coolant subjected to constant heat flux 10 W/cm 2 , for Reynolds number ranging between 100 and 900 was considered for the study. Extended surfaces of different shapes namely, square and circular with staggered arrangement was considered for both micro pin fin heat sink and micro channel pin fin heat sink. Two non-dimensional parameters namely Nusselt number and thermal performance index were employed to access the performance of heat sink. Results indicate that the microchannel pin fin heat sink has highest nusselt number and friction factor over the whole Reynolds number range. Results also revealed that formation of secondary vortices enhances heat transfer in micro channel heat sink with square pin fin compared to micro channel heat sink with circular pin fin. However, pin fin heat sink has better thermal performance index compared to Micro channel pin fin heat sink and is more preferable when heat dissipation is compared with pressure drop penalty. The Governing equations for fluid and solid domain were solved using FLUENT to study flow and heat transfer characteristics.