Channel interlacing: A geometric concept for intensification and design of the internal structure of fluid contactors

This paper introduces a new concept of intensification of mixing and/or transfer, based on the “interlacing” of the flow channels of two or more distinct arborescent (dendritic) networks, thus creating a new method for multi-vascularization of a specific space. These complex geometries are materialized by 3D manufacturing techniques of the family of stereolithography, which are briefly discussed.Interlaced arborescences achieve intensification not only through the conventional effect of dividing incoming flows into smaller channels with subsequent increase of interfacial areas, but also through the new patterns of interface it generates and through the micro-turbulence generated by the tortuosity of the channels. The two geometric operations constitutive of interlacing are introduced: “chiasma”, i.e. permutation of the position of two neighbor channels, and division of the channels into several sub-channels by introduction of new separating walls. Specific generic combinations of chiasma and divisions constitute the toolbox from which generic configurations can be produced, which can be multiplied at different scales according to the constructal principle , and the methodology is developed to rationally design functional devices using these principles. The approach is illustrated with examples of a heat exchanger for two fluids, and of a reactor-exchanger where two reacting fluids are mixed, and exchange heat with a third fluid. The approach is applicable to a larger number of fluids though. These examples are presented on the basis of channels with a basically square cross-section. It is then shown how other cross-section geometries may be used, in particular using triangles, to pack hexagonal or quasi-circular spaces.