“Passive safety is the most important feature of NuScale’s reactor designs. Twist tape is one passive heat enhance heat technique. The present research investigated thermo-hydraulic characteristics of natural and forced convection of water under different configurations of twisted tape inserted in tube as well as NuScale rod bundles for uniform wall heat flux using computational fluid dynamics (CFD) using ANSYS Fluent 18.1. Results for twist tape inserted in tube under natural circulation showed that heat transfer enhanced and pressure drop increased to 28% and 102.8% over the plain tube respectively. Regularly spaced tapes, and different widths of the twisted tapes also played a significant role in both heat transfer and pressure drop. Moreover, the results revealed a strong effect of twist ratios on the inner wall temperature. The impact of twisted tapes along sub-channel for the water flow through NuScale SMR’s 2X2 RB at the normal operating conditions showed that the Nusselt number (Nu) and secondary flow were enhanced by 101% and 0.16 as compared to the case of plain sub-channel, respectively. On the other hand, the pressure drop for a sub-channel with twisted tape is always higher than the plain sub-channel. The flow in rod bundle sub-channels under natural convection with twist along the sub-channel showed that heat transfer and pressure drop are increased by 39.5% and 112.5% as compared to the case of plain sub-channel respectively. In addition, all results showed that Nu and pressure drop are influenced by changing the twist ratio, and tape geometry. Finally, twisted tapes were effective in enhancing the Nu in sub-channels under both natural and forced convection conditions. The smallest twist ratio in all cases resulted in the high pressure drop and Nu”--Abstract, page iii
