Optimization method for compact heat exchanger cores with circular channels

Geometry optimization aims to maximize heat transfer rate and minimize pressure drop attending to structural and fabrication constraints. The present work carried out the first optimization study of compact heat exchangers produced by selective laser melting (SLM) with circular channels. No optimization study investigated circular mini channels since most focus on semi-circular channels of printed circuit heat exchangers. Besides, since samples produced by selective laser melting present higher yield strength, it was possible to investigate a higher range of configurations. Analytical models of heat transfer and pressure drop, with structural analysis in finite element model were used in the optimization study. The analysis was conducted using genetic algorithms (NSGA-II) based on evolutionary and dominance concepts to evaluate different configurations. The results showed a strong relationship with the admissible stress limit, so a new study, using the properties SLM samples, was performed. Decision variables’ behavior was investigated among all the optimum solutions, besides stress constraint and flow type (cross and counter-flow), resulting in different optimal solutions of Pareto curves. The optimization provided heat transfer and pressure drop ratio from 1.2 kW/Pa to 12.5 kW/Pa. The optimized arrangements were compared with heat exchangers from the literature, demonstrating a 19% improvement in thermal performance and an 85% reduction in pressure drop.