In this study, a scale thermal energy storage tank with the function of the stratified charging and discharging was established, and the influence of the change of the position of inlets and outlets on the water thermal stratification was studied experimentally. The research revealed that the water flow between the intake and return can be approximate as the "piston flow" when the return port is located at the bottom of the tank and the return water temperature is equal to or less than the bottom temperature of the tank; The location of the outlet has a significant impact on the thermal stratification of the water body. When the relative height of the outlet increases successively by 0.2, 0.4, 0.6, and 0.8, the MIX number increases by 12.1%, 11.9%, 15.2%, and 20.3% during the same discharge period, respectively. This indicates that the higher the outlet position is, the faster the thermal stratification of the water body decreases. Therefore, in the design and operation of the thermal storage tank, the appropriate location of the outlet should be chosen based on actual needs to minimize its impact on water thermal stratification; The existing Ri number model is not intuitive enough to represent the changes in water thermal stratification caused by variations in the water intake port location. In contrast, the MIX number or the thickness of the thermocline can better reflect the changes in water thermal stratification resulting from variations in the height of the outlet. Furthermore, the height of the inlet needs to be determined based on the return water temperature to ensure that the return water temperature is close to the water temperature at the return port location, thereby reducing the disruption to the thermal stratification of the water body.
Key words
solar energy /
heat storage /
discharge /
thermal stratification /
pit thermal energy storage （PTES） /
scale model experiment
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