Natural branching - inspired heat exchanger design for heat transfer enhancement

The ubiquity of heat exchangers, coupled with the urgent need to augment energy efficiency in the green transition of industries, underscores the importance of optimizing the flow-field design to maximize heat transfer. Inspired by nature-evolved transport networks (e.g., tree branches), this study explores 3D three-level trifurcating pipe networks with varying branching angles (20° - 65°) as alternatives to conventional vertical pipes. Three key conclusions are highlighted. Firstly, steep temperature increases at junctions lead to distinctly different heat transfer and flow behaviors in the middle level among the geometries. Secondly, the relationship between the Re-normalized thermal performance factor (TPF) is non-monotonic with respect to angle, with the 36° model giving the highest TPF/Re value. Thirdly, the superior performance of the 36° model is associated with the lowest mean normalized turbulent viscosity (µ_t/Re) and highest mean normalized vorticity (ΩD/U), suggesting the flow is dominated by coherent rotational strcutures rather than chaotic, dissipative turbulence. These coherent vortices could be leveraged - by judiciously mimicking the 36° configuration - to further enhance thermal performance. Furthermore, the difference in turbulent viscosity between the outer and central pipes in the top level is the least for the 36° model, indicating enhanced uniformity. These findings offer insights for designing efficient, nature-inspired heat exchangers.