Computational thermal-hydraulic analysis and geometric optimization of elliptic and circular wavy fin and tube heat exchangers

The three-dimensional (3D) fluid flow and heat transfer analysis and geometric optimization of two rows circular and elliptic wavy fin and tube heat exchanger (FTHE) are numerically examined for staggered arrangement. Numerical optimization studies are carried out with modeFRONTIER 2021R3 commercial software and computational fluid dynamics (CFD) analysis are conducted with help of the ANSYS Fluent R2021a which is based on the finite volume method under the assumptions of incompressible, steady and turbulent flows, and conjugate heat transfer. The circular wavy FTHE is validated with the experimental data that is conducted in the literature. In the present work, two optimization cases are solved: (1) unconstrained optimization of circular wavy FTHE (2) constrained optimization of elliptic wavy FTHE. The optimization problems have more objectives, so they are treated as multi-objective design problems. The objectives of unconstrained optimization of circular wavy FTHE case are to obtain maximum heat transfer, minimum pumping power and minimum volume. The objectives of constrained optimization of elliptic wavy FTHE case are the maximization of heat transfer and minimization of pumping power, where the constraints are given using the optimum design values of circular case to get better designs. The performance of the circular and elliptic wavy FTHE is compared in tabular and graphical forms in terms of Colburn factor j, friction factor f, heat transfer, pumping power, fin efficiency, volume, and thermal-hydraulic performance (THP) parameter. The pumping power is seen to be reduced when elliptic geometries are used in FTHEs. This is due to the streamlined shape of tubes, which causes delays in the separation point and reduction of vortices in the wake region. For the optimum design chosen from Pareto designs, elliptic wavy FTHE outperforms circular wavy FTHE in terms of THP and fin efficiency by 111.9% and 3.2%, respectively.

Automated summary

This study investigates the 3D fluid flow and heat transfer analysis as well as geometric optimization of two rows circular and elliptic wavy fin and tube heat exchangers (FTHEs). The performances of circular and elliptic FTHEs are compared through numerical optimization and CFD analysis, and it is found that the elliptic FTHE outperforms the circular FTHE in terms of thermal-hydraulic performance and fin efficiency.