Heat transfer/pressure drop correlations and core optimization of airfoil tube heat exchangers

Abstract

Abstract This study proposes a methodology for acquiring heat transfer and pressure drop correlations for compact heat exchangers (HXs), leveraging modern manufacturing techniques such as additive manufacturing to enable unconventional geometries and to support preliminary design of novel core concepts for a hybrid-electric case-study aircraft. In addition, this study investigates an airfoil-based HX concept compared to conventional designs. The methodology combines sensitivity analyses, virtual experimental testing through Computational Fluid Dynamics (CFD), lumped-parameter modeling, and nonlinear regression fed by 1,209 CFD simulations. The proposed HX was defined through analytical equations regressed from the results and applied to lumped-parameter models simulating thermal-hydraulic behavior. From a nondimensional comparison, the airfoil HX exhibited lower $$\:j$$ - and $$\:f$$ -factors but achieved a median $$\:j/f$$ ratio up to six times higher, and the best case is approximately 11% superior to the best conventional HX. Dimensional comparisons were conducted through extensive lumped-model Design of Experiments, equating heat exchangers using different comparison variables. In this approach, some hypotheses were refuted, as conventional designs retained advantages in frontal area and heat transfer area optimization. However, in volume minimization, the airfoil HX achieved reductions of 87% compared to the best conventional core. In this case, CFD verification also confirmed deviations within ± 15%. Overall, the proposed methodology validates the robustness and feasibility of combining CFD sensitivity studies, nonlinear regression, and multivariate optimization to novel HXs. Although certain initial hypotheses were refuted, the airfoil-based HX demonstrates potential for volume-focused applications, guiding future opportunities in thermal management systems for transportation and industrial contexts.