Thermodynamic optimization in heat transfer

This keynote paper reviews a modern transformation in heat transfer: the increasingly important roles played by thermodynamics principles and design considerations in problem formulation. Thermodynamic optimization, or entropy generation minimization is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite-size constraints. The method is illustrated by means of examples from cryogenic insulation, heat exchangers, the cooling of electronic packages, and power and refrigeration plants. The concluding section outlines the recently proposed constructal theory: the geometric minimization of the thermal resistance in systems with internal flows, i.e., far from equilibium. The discovery is that every volume element can have its shape optimized such that its own volume-to-paint resistance is minimal. Optimally shaped elements are grouped into a construct, and the shape of the construct is optimized. One feature of the emerging heat flow path is a tree network that is completely deterministic. The paper ends with a discussion of the constructal law as the generating principle for macroscopic shape and structure in natural flow systems, animate and inanimate.