Helical airfoil corrugated tubes: A numerical comparison with common corrugated profiles and geometrical optimization by multi-objective algorithm

Abstract

In this study, helical airfoil corrugated tube (HACT) has suggested to improve the heat transfer capabilities of the tube heat exchanger. Firstly, thermal-hydraulic performance of HACT is numerically compared with common helical corrugated tube (HCTs) such as helical semi-ellipse corrugated tube (HSECT), helical semi-circle corrugated tube (HSCCT) and smooth tube based on thermal performance parameters: Nusselt number (Nu), friction factor (f) and performance evaluation criteria (PEC). Helium under high Reynolds number (Re) is the working fluid of this study. By analyzing the numerical outcomes, it is found that HACT has the heat transfer coefficient roughly 4 % higher than that of HSECT, around 5 % higher than that of HSCCT and more than 60 % higher than that of smooth tube. Then, a multi-objective optimization (MOO) is carried out to optimize the geometrical configuration of HACT. Initially, a numerical experimental design is constructed using the Box-Behnken method within the response surface methodology (RSM), focusing on two objectives and three factors. Subsequently, significant regression models (SRM) are derived via analysis of variance (ANNOVA). Then, leveraging these significant regression models of Nu and PEC, the geometric optimization of HACT is executed using Non-dominated Sorting Genetic Algorithm (NSGA-II), ultimately leading to the attainment of the Pareto front. Finally, based on Pareto optimal set, Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method was applied for decision-making involving multiple objectives.