Thermal performance of dimpled/protruded circular and annular microchannel tube heat sink

Flow characteristics and heat transfer performance in the circular and annular microchannels with dimples/protrusions are studied numerically. The effects of Reynolds number (Re), dimple/protrusion size, combinations of dimples or protrusions, and arrangement pattern are examined. The results show that in circular microchannels, dimple cases show the poor heat transfer capacity and the staggered dimple case provides no significant difference. The aligned protrusion cases provide excellent heat transfer performance, which is further improved with the increase in protrusion size or Re, and the staggered protrusion case shows the worse heat transfer performance. In annular microchannels, the outer protrusion shows the better heat transfer effect superior to the inner protrusion. In protrusion microchannel, it will be helpful in avoiding the excessive additional flow resistance when dimples are fixed on the opposite wall. The arrangement has no significant effect on the heat transfer and friction characteristic, and the flow separation on the dimple (protrusion) side is suppressed when the protrusion (dimple) is fixed on the opposite wall. From the view point of energy saving, in circular microchannels, the protrusion cases provide the high effectiveness, and the staggered case possesses the lower effectiveness especially in the protrusion case. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.