Parametric study on the effect of endwalls on fluid flow in micro pin-fins

Micro pin-fin heat sinks have been considered as new generation micro heat sinks and may find applications in many fields such as microreactor, electronics cooling, micro turbine cooling and microbiological applications. The flow across micro pin fins can be considered as cross flow across intermediate size (based on the height-diameter ratio, H/D ratio changes from 1/2 to 5) fins, whose thermal and hydraulic performances are different from long conventional tubes due to the effects of endwalls on the both thermal and velocity boundary layers as well as low flow rates. The endwalls effects imposed by the microchannel having micro pin fins have not been extensively discussed in the literature since mostly long fins have been used at high flow rates, where such effects were mostly negligible. This article intends to address to the lack of information on endwalls effects on heat and fluid flow in micro pin fin heat sinks having intermediate size pin fins under broad working conditions. Water was used as working fluid in the following Reynolds number ranges (1<Re<1000). Heat flux was changed from 30W/cm2 to 60W/cm2. As a result of extensive parametric investigation, it is observed that the velocity field, friction factor and heat transfer across the micro pin fin surface significantly are affected by the endwalls.