不同结构填充床蓄热罐换热特性及分层性能研究

Study on Heat Transfer Characteristics and Stratification Performance of Packed Bed Thermal Storage Tanks With Different Structures

斜温层单罐蓄热技术是太阳能热发电、热电厂热电解耦和工业余热利用等方向的重点研究内容。为了研究多级相变材料和多层相变单元球径对储罐内部换热性能及热分层性能的影响,建立了四种不同结构的填充床相变蓄热罐。研究了四种储罐在蓄热过程中的相变材料温度分布、换热流体温度分布、总换热量及换热速率的大小,并引入了理查森数和混合数对四种储罐的热分层性能进行评估。结果发现:采用3级相变材料与3种球径搭配的填充床储罐,其换热性能和热分层性能最好;且与仅使用单级相变材料和单球径搭配的储罐相比,其换热速率提高了17.08%;蓄热结束时的理查森数提高了52.27%,混合数降低了26.19%。该研究可为优化填充床相变蓄热罐的罐内热分层性能提供参考。

The thermocline single-tank heat storage technology is the key research content in the fields of solar thermal power generation, thermoelectric coupling in thermal power plants, and industrial waste heat utilization. In order to study the effects of multi-stage phase change materials and multi-layer phase change unit diameters on the internal heat transfer and thermal stratification performances of the storage tank, four types of packed bed phase change heat storage tanks with different structures were established. The phase change material temperature distribution, heat transfer fluid temperature distribution, total heat transfer and heat transfer rate of the four storage tanks in the heat storage process were studied, and the Richardson number and MIX number were introduced to evaluate the thermal stratification performance of the four storage tanks. The results showed that the packed bed storage tank with 3 levels of phase change material and 3 kinds of spherical diameters present the best heat transfer and thermal stratification performances. Compared with the storage tanks that only adopt single-stage phase change material and single spherical diameter, the heat transfer rate increased by 17.08%, the Richardson number at the end of heat storage increased by 52.27%, and the MIX number has been reduced by 26.19%. This study can provide a reference for optimizing the thermal stratification performance of the packed bed phase change thermal storage tank.