Constructal Evolution of Networks of Exergy Flows

The Constructal Principle was formulated by Bejan as a fundamental Physical Principle, with the same generality as the First and Second Laws of Thermodynamics [1]. Then, it has been shown that it can be considered an extension of the Maximum Entropy Production Principle [2] and has been used in the literature to explain the shape and structure of many flowing systems [3]. The constructive principle states that the shape of that structure must evolve in the direction that allows for higher flow through the domain, and in many cases, the result is a tree-shaped structure [3]. Very few papers in the literature deal with discrete network systems, even if the general validity of the Constructal Principle is not limited to continuous media. In the paper, a special class of discrete system is considered, made up of a network of exergy fluxes, whose nodes are the exergy conversion processes, where the exergy destruction takes place, whilst the arcs represent the exergy flows exchanged among the nodes, or with the outside (see figure 1). The network takes its primary exergy resources ( 𝐹 𝑇 𝑗𝑖 ) from the outside environment and produces some kind of product (P i ) for the outside or its own growth.