搭建具备分层取、回水功能的缩尺蓄热水池实验平台,通过实验方法研究取热过程中取水口和回水口位置改变对水体热分层的影响。研究表明埋地蓄热水池在取热运行工况下,当回水口位于水池底部,且回水温度小于等于水池底部温度时,取、回水口之间的水体流动可近似认为是“活塞流”;取水口位置对水体热分层有较大影响,当取水口相对高度依次按照0.2、0.4、0.6、0.8增大时,在相同取热时间段内混合数Nmix依次增加12.1%、11.9%、15.2%、20.3%,这表明取水口位置越高水体热分层程度减小得越快。因此在蓄热水池设计和运行过程中应根据实际需求选择合适的取水口位置,尽可能降低对水体热分层的影响;现有理查森数Ri模型在表征取水口位置变化引起的水体热分层变化时不够直观,而采用Nmix指标或温跃层厚度能够较好反映由取水口高度变化导致的水体热分层变化。回水口高度需根据回水温度来确定,尽可能使回水温度与回水口所处水体温度相近以减少对水体热分层的破坏。
Abstract
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.
关键词
太阳能 /
储热 /
取热 /
热分层 /
蓄热水池 /
缩尺实验
Key words
solar energy /
heat storage /
discharge /
thermal stratification /
pit thermal energy storage （PTES） /
scale model experiment
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基金
国家自然科学基金青年项目（52108094）; 十四五”国家重点研发计划项目课题（2022YFC3802705）
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