Constructal approach and multi-scale components

The constructal approach, proposed by Bejan is an emergent notion which quickly develops at the international level and in a multi-disciplinary frame. It is a method of optimization of the conception of objects and “components” which allows finding the geometry of a multi-scale system in view of an optimal performance. The constructal concept, as the fractal concept, is a way of connecting the geometry of a microscopic world (the structures of an equipment or a material at the finest scales) with the macroscopic world in which it is immersed, through several intermediate scales. Essential differences with the fractal object are that the constructal object optimizes the passages from one scale to the other, that the geometry is not necessarily invariant from one scale to the other, and that there maybe some thermodynamic content to the optimization, such as minimizing entropy production. The present paper addresses these issues through several aspects: general introduction to the constructal approach; discussion of some examples of multi-scale components (heat exchanger, fluid distributor, coupling of fluid distributor to heat exchanger, mixer and its coupling to a micro reactor); manufacturing issues; perspectives for applications and for further scientific research.