Model for heat transfer between buffer storage layers.
Models conductance of water and buoyancy according to Viskanta et al., 1997. An effective heat conductivity is therefore calculated. Used in BufferStorage model. In addition, the smooth() expression is used for the transition of the buoyancy model.
R. Viskanta, A. KaraIds: Interferometric observations of the temperature structure in water cooled or heated from above. Advances in Water Resources, volume 1, 1977, pages 57-69. Bibtex-Key [R.VISKANTA1977]