Stable stratification and adequate mixing are important means for the heat storage tank to achieve the two functions of efficient heating and constant temperature water output. This work designed a stratified-mixing integrated heat storage tank, which can realize the effective switching of two functions, and meet the flexible needs of stratified high-efficiency heating and constant temperature domestic hot water in different periods or different seasons. In this study, a set of thermodynamic characteristics test experimental system of the heat storage tank was built, using stratification efficiency, exergy efficiency and other evaluation indicators to study the thermodynamic performance and dynamic response characteristics of the stratified-mixing heat storage tank under different sizes, flow rates and temperatures. Taking a 125 L experimental heat storage tank as an example, the results show that： in the stratification mode, the thermal stratification rate and stability are significantly better than that of the conventional heat storage tank, the exergy efficiency and stratification efficiency are obviously improved, and the exergy efficiency can reach more than 90%. In the mixing mode, the mixing speed is significantly increased, and the stratification efficiency is quickly reduced to 0.10, which realizes the complete mixing of the heat storage tank, which has certain guidance for the development and application of the stratification-mixing double-effect heat storage tank.
Key words
solar water heating system /
heat storage water tank /
thermal stratification /
mixing /
exergy efficiency /
stratification efficiency
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