Numerical investigation of the hydrothermal performance of novel vortex generators in a rectangular channel by employing inclination and rotational angles

Abstract

Vortex generators are passive methods of heat transfer enhancement in any thermal system. However, more research is needed to compare the effects of vortex generators having unique shapes on the flow distribution for high heat transmission. Also, a research gap exists in analyzing how different angular orientations of the vortex generator (VG) affect thermohydraulic performance. Therefore, this CFD study aims to propose a total of five novel vortex generator shapes applying modification on a rectangular VG shape, analyzing and comparing the heat transfer and pressure drop properties in a rectangular channel for the Reynolds number varying in the range of Re=4000–11,000. VG-1 (vortex generator-1) with three triangles on its top side, VG-2 with concave shape arc, VG-3 combined with a rectangle and a triangle, VG-4 consists of a rectangle and two triangles at two corners, while VG-5 consists of a rectangle with a triangular inside cut. Among the five designs, VG-1 gives the most optimal hydrothermal performance, incrementing Nusselt number and friction factor of about 38.2 % and 80.38 %, respectively. Combining these two dimensionless parameters, we get the maximum thermal performance factor, TPF, for VG-1, whereas VG-2 performs the least in terms of TPF. Moreover, compared with conventional rectangular VG, VG-1 performed the best with a 1.63 % increase in TPF. Considering the effect of different angular orientations, VG-1 was further studied by applying five vertical inclination angles and four horizontal rotation angle configurations to investigate the impact of inclination and rotational angles. Minimizing the pressure drop penalty, the 30˚ inclination design had the best hydrothermal performance overall, with the highest TPF range of 1.19–1.41, whereas 120˚ variants had the lowest TPF, at 1.09–1.31. Also, for the configuration of the horizontal rotations, 30˚ angle gives the best result, having a slight edge over 150˚case with 1.17–1.41 TPF. Finally, the best cases from vertical inclination and horizontal rotation are combined in a new hybrid configuration, which yielded the maximum TPF of 1.22–1.45, indicating that this configuration is the most effective among all the cases.

Keywords

• CFD
• Vortex generators
• Heat transfer
• Inclination angle
• Nusselt number
• Thermal performance factor