Studies on heat transfer in flow of silver nanofluid through a straight tube with twisted tape inserts

Convective heat transfer in the flow of silver nanofluid through a straight tube with twisted tape inserts was investigated experimentally. This straight tube was used as absorber/receiver tube in parabolic trough collector. The experiments were conducted for Reynolds number range 500 < Re < 6000 with twisted tape inserts of different twist ratio range 0.577 < H/D < 1.732. This experimental study shows that twisted tape inserts enhances heat transfer rate in the tube. The heat transfer coefficient and friction factor in the flow of silver nanofliud with 5 % volume fraction (concentration) are higher compared to the flow of water. From this study, Nusselt number, friction factor and enhancement factor are found as 2.0-3.0 times, 10-48.5 and 135-175 %, respectively with silver nanofliud. Finally new possible correlations for predicting heat transfer and friction factor in the flow of silver nanofliud through the straight tube with twisted tape inserts are proposed.