DYNAMICS OF LATENT HEAT STORAGE IN FIXED BEDS A NON-LINEAR EQUILIBRIUM MODEL-THE ANALOGY WITH CHROMATOGRAPHY

This paper investigates theoretically the dynamics of a latent heat storage system consisting of a fixed bed operating close to thermal equilibrium with a percolating fluid. The model used is an idealized one, which emphasizes the role of the heat capacity factor, but neglects heat transfer resistances, losses, and hydrodynamic non-idealities. The approach is shown to resemble that used classicaly in non-linear adsorption, and analogous concepts, such as shock waves and dispersive waves are introduced. The shapes and propagation characteristics of the temperature profiles generated during loading and unloading of the bed are discussed, for various fusible materials, operating temperatures, initial and boundary conditions, and flow direction. The non-linear dependence of the enthalpy of the storage material on temperature is shown to play a central role in determining the qualitative features of these profiles. The aims of the article are mainly qualitative, conceptual and didactic.