Multi-objective optimization of thermo-hydraulic behavior of heat exchanger with v-cut twisted tape in axial and radial direction using NSGA-II

Abstract

ABSTRACT In pursuit of optimizing the thermo-hydraulic behavior of a heat exchanger, this study employs twisted tape inserts, a well-known method for enhancing heat transfer rates in heat exchange devices compared to plain tubes. Experiments involving v-cut twisted tapes with v-angles of 15°, 30°, and 45° in both axial and radial directions were conducted within a double pipe heat exchanger, encompassing a Reynolds number range from 5500 to 10,000, with water as the flowing medium. As part of the modeling approach, response surface methodology (RSM) was harnessed to construct mathematical models for the heat transfer rate, quantified as the Nusselt number, and the friction factor. This modeling accounted for independent variables including Reynolds number, Prandtl number, axial angle, and radial angle. The RSM models demonstrated high statistical significance and reliability, yielding an R-squared value exceeding 97%, with the linear terms of Reynolds number and cut angles identified as the most influential factors. To attain optimization, a multi-objective approach was adopted, employing the NSGA-II algorithm. This algorithm efficiently explored the design parameter space, seeking the optimal combination that maximizes heat transfer rate and minimizes the friction factor simultaneously. Quantitative results from the experimentation revealed that, at a Reynolds number of 10,000, the Nusselt number achieved its peak value of 96.51. Conversely, the highest friction factor (0.0582) and performance evaluation criteria (PEC) of 1.65 emerged at a Reynolds number of 5500, specifically when employing a 45-degree radial v-cut angle. Notably, this configuration led to substantial enhancements: the Nusselt number increased by 98.7%, the friction factor by 38.9%, and the PEC by 39.4% compared to a plain tube. These findings underscore both the effectiveness of the NSGA-II algorithm in optimizing heat exchanger designs and the valuable insights gained into the influence of twisted tape insert parameters on heat transfer performance and hydraulic behavior. The optimized design parameters obtained through this study hold significant potential for enhancing heat transfer efficiency across diverse industrial applications. Overall, this research advances heat exchanger optimization techniques and provides a framework for further investigations in this field.