MIXING IN THERMALLY STRATIFIED ENERGY STORES

Two important aspects of short-term thermally stratified energy storag e, thermocline mixing and thermocline thickness, are studied analytica lly, experimentally and numerically The storage detrimental aspects ar e investigated for a simplified configuration, i.e. an adiabatic box c ontaining a quasi-stationary thermocline. Numerical finite difference/ volume simulations agree well with experiments. The dissipation-free 1 D analytical model shows a large discrepancy. It appears that mixing i nside thermally stratified stores is a two-stage process. First fluid is withdrawn from the thermocline by viscous drag. Subsequent mixing t akes place by stretching and folding of fluid particles, thereby enabl ing diffusion to become active. Copyright (C) 1996 Elsevier Science Lt d.