The Effects of Boundary Design on the Efficiency of Large-Scale Hot Water Heat Stores

Boundary design of stratified hot water heat stores is important not only to minimize the thermal losses to the ambient but also to preserve the thermodynamic quality of the stored energy. A new method of characterization, which equivalently accounts for both these concerns, is applied in this paper to investigate into the boundary design of large-scale hot water heat stores. A variety of concepts related to general design of the containments, namely, the effects of the thermal conductivity and thickness of the container wall, are numerically analyzed. The design insights provided by the analysis are in good agreement with the corresponding experimental results for small-scale hot water heat stores found in the literature. Different ways of insulation application, differential application of the external insulation, and insulation of the top walls are further investigated to obtain ideas for the efficient use of the insulation material. The new characterization scheme proves to be an efficient tool to rank the performance of different boundary designs during storing process of large-scale stratified hot water heat stores and to provide valuable design insights. [DOI: 10.1115/1.4004472]