Constructal geometry and operation of adsorption processes

This paper shows that the temporal and spatial structure of adsorption–desorption processes can be optimized for maximal packing of mass transfer into a fixed space, and for minimal overall pumping power. In the first part of the paper, simple models demonstrate that the periodicity of such processes can be optimized in three settings: fixed desorption time, variable desorption time, and variable species concentration in the gas space. The second part of the paper shows how the optimized time scales determine the dimensions of the smallest flow channels—the elemental system. The available space can be packed with elemental systems in a hierarchical (constructal) structure [Bejan, Shape and Structure, from Engineering to Nature, Cambridge University Press, 2000], in which elements are assembled into first constructs, first constructs are assembled into second constructs, etc. The robustness and nearly optimal performance of the optimized mass exchanger structure is discussed.