Thermal performance of Ag-water nanofluid in tube equipped with novel conical strip inserts using two-phase method: Geometry effects and particle migration considerations

This paper attempts to evaluate hydrothermal attributes and energy efficiency of the water-Ag nanofluid in a circular tube equipped with twisted conical strip inserts through the two-phase Eulerian-Lagrangian method. Different alignments including one-, two- and three-blade configurations for the strip inserts are investigated. The new inserts under evaluation are a combination of conical strip inserts and twisted tape inserts. In the simulations, different forces including thermophoretic force, drag force, lift force and Brownian force are considered. The Nusselt number enhances by increasing Reynolds number, while reduces with twist angle increment. Moreover, the friction factor decreases by increasing either Reynolds number or twist angle. The effect of alignment type is more obvious at smaller twist angles and higher geometry angle. Changing the geometry angle affects Nusselt number and friction factor for the two-blade alignment, while it has not a significant influence for the one-blade alignment. The results show that nanoparticle dispersion is more intense at smaller twist angles, and intensifies by increase of the distance from the tube inlet. Moreover, the one-blade alignment demonstrates a higher PEC than other configurations. Furthermore, the minimum PEC happens in the three-blade configuration at twist angle of 5 degrees and geometry angle of 60 degrees. (C) 2018 Elsevier B.V. All rights reserved.