Thermal Performance of Pin Fins at Low Reynolds Numbers in Mini-Micro-Channels

The computational study investigates different pin fin arrangements at low Reynolds numbers, which would typically be prevalent in mini-micro-channels used in enhancing heat as well as mass transfer. The effect of pin density, span-wise pitch, and stream-wise pitch is investigated on friction and heat transfer over a range 5<Re_D<400. High density pins with small span-wise pitches were found to provide the highest augmentation in heat transfer capacity (conductance), whereas low density pins with or without a large stream-wise pitch were found to provide the least heat transfer benefits in the low Reynolds number range studied. Friction factor decreases considerably as the pin density decreases. The effect of decreasing span-wise pitch increases the friction factor in the low Reynolds number regime (Re_D<200) but decreases it beyond Re_D = 200 by delaying wake instabilities and the associated increase in form drag. Increasing the stream-wise pitch decreases the friction factor at low Re_D<200, but increases it at Re_D>200 due to the formation of larger recirculating wakes. Overall it is concluded that a high density arrangement with a small span-wise pitch provides the best thermal performance.