Constructal theory of energy-system and environment flow configurations A. Bejan* Duke University, Department of Mechanical Engineering and Materials Science, Durham, NC 27708-0300, USA E-mail: dalford@duke.edu *Corresponding author S. Lorente Laboratoire MateÂriaux et Durabilite des Constructions, Institut National des Sciences AppliqueÂes, DeÂpartement de GeÂnie Civil, 135 Avenue de Rangueil, 31077, Toulouse, France E-mail: lorente@insa-toulouse.fr Abstract: This paper outlines the place occupied by the constructal law in thermodynamics, and provides a vision of the future development of energy engineering as a transdisciplinary science of systems of systems. Natural and man-made flow systems do not exist in isolation. The optimal balance between engineered flow systems and their surroundings is achieved through the optimal distributing of thermodynamic imperfections. The paper traces the development of constructal theory from a principle of maximisation of flow access in morphing configurations to engineering discoveries, such as optimal internal spacings, tree-shaped flow networks, machine flight, and multi-scale flow structures for maximal heat transfer density. The introduction of constructal theory and design in thermodynamics education is also discussed. Keywords: constructal; dendritic; energy; environment; flight; multi-scale; tree networks. Reference to this paper should be made as follows: Bejan, A. and Lorente, S. (2005) `Constructal theory of energy-system and environment flow configurations', Int. J. Exergy, Vol. 2, No. 4, pp.335±347. Biographical notes: Adrian Bejan received his degrees (BS, 1971; MS, 1972; PhD, 1975) in mechanical engineering from the Massachusetts Institute of Technology. He has held the J.A. Jones Chair at Duke University since 1989. His work covers a diversity of topics in convective heat transfer, engineering thermodynamics and constructal theory and design. Professor Bejan is ranked among the 100 most cited authors in engineering, all disciplines, all countries (www.isihighlycited.com). Sylvie Lorente received the 2005 Bergles-Rohsenow Young Investigator Award in Heat Transfer from the American Society of Mechanical Engineers. She received all her degrees in civil engineering (BS, 1992; MS, 1992; PhD, 1996) from the National Institute of Applied Sciences (INSA), Toulouse. She has been Associate Professor of Civil Engineering at INSA Toulouse Int. J. Exergy, Vol. 2, No. 4, 2005 335 Copyright # 2005 Inderscience Enterprises Ltd.