Numerical investigation and experimental validation of thermo-hydraulic and thermodynamic performances of helical baffle heat exchangers with different baffle configurations

Abstract

Helical baffle is deemed as a favorable substitute for segmental one. In the present paper, the investigations on fluid flow and heat transfer behaviors are conducted for heat exchangers with eight helical baffle configurations, involving the continuous helical (CH) scheme, quadrant helical (QH) scheme with diverse axial overlapped ratios and novel sextant helical (SH) scheme. The second law of thermodynamics analysis is exploited to further evaluate the irreversibility in helical baffle heat exchangers. Verifications between the experimental data and numerical predictions are performed, and a good agreement is achieved. The parallel and rotational components decomposed from shell-side velocity are detected, and a new conception of the swirl angle is advanced to reveal the stream pattern in helical channel. The leakages passing through conjunction notches between adjacent baffle plates are depicted to check the discrepancy between the spiral and pseudo-spiral flow states. It concludes that the alterations of baffle shapes and assembly arrangements influence the flow field properties significantly. By analyzing the heat transfer, resistance and comprehensive characteristics in shell side, the SH scheme possesses better thermo-hydraulic performance than the CH and QH schemes; moreover, the least entropy generation is received in the SH and QH schemes at low Reynolds number. In addition, larger axial overlapped ratio provides greater heat transfer coefficient and pressure drop but smaller their ratio as well as higher thermodynamic irreversible loss.