Performance investigation and multi-objective optimization of helical baffle heat exchangers based on thermodynamic and economic analyses

Abstract

The application of helical baffle heat exchangers (HBHXs) is attracting much more attention in both industrial and academic fields. In this paper, the heat transfer and fluid flow characteristics of HBHXs are explored by the aid of numerical and experimental analyses, and a good agreement is reached between the simulated and measured data. A series of helical baffle configurations involving parameter combinations of helix angles (10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°) and axial overlapped ratios (0, 10%, 20%, 30%, 40%, 50%) are taken into account. Then a multi-objective genetic algorithm approach is proposed for HBHXs optimization design. The tube number, tube outer diameter, tube length, helix angle and axial overlapped ratio are perceived as design variables, and the revised entropy generation number and total cost are considered as objective functions. The results illustrate that the thermal enhancement and axial velocity reduction are attributed to diminished helix angle and enlarged axial overlapped ratio. For the sake of a narrow helix pitch, the baffle schemes of 45° helix angle together with no more than 20% axial overlapped ratio are given priority over the one of 40° helix angle, while the schemes of 40° helix angle as well as at most 30% axial overlapped ratio are preferable to the one of 30° helix angle in view of better shell-side comprehensive performance. A set of Pareto optimal solutions are obtained in order to trade off the thermodynamic and economic behaviors, and the optimized results make known that the multi-objective optimization method is more suitable compared with the single-objective optimization strategy.