901 publications from this institution
This paper documents the fundamentals of heat storage by melting a phase-change material inside a cylindrical enclosure with a vertical heated pipe on its axis. The phenomenon is studied analytically and numerically. The analysis consists of the scale analysis of the early stages of natural convection in the liquid, and an analysis of the entire duration of the melting process. The numerical simulations cover the entire process, and validate all the features predicted by theory.
This is a review of recent engineering developments in thermodynamic optimization, which shed light on a universal design principle that accounts for macroscopic organization in nature. It is shown that the optimal performance of a finite-size system with purpose is always characterized by the equipartition of driving forces or the optimal allocation of material subject to overall constraints. Examples are drawn from natural inanimate systems (river basins, turbulent flow) and animate systems (living trees). It is shown that this principle also governs the architecture of tree networks. Tree networks can be obtained in purely deterministic fashion by minimizing the flow resistance (or the time of travel) between one point and a finite area or a finite volume (an infinite number of points). The shape of each volume element can be optimized for minimal flow resistance. The network is ‘constructed’ by assembling the shape-optimized building blocks, and proceeding in time from the smallest volume element toward larger constructs. In constructal theory small size and shapeless flow (diffusion) come first, and larger sizes and geometrical form (channels, streams) come later.
