U型管式相变蓄热真空太阳集热管结构优化与性能分析

STRUCTURAL OPTIMIZATION AND PERFORMANCE ANALYSIS OF U-TUBULAR PHASE CHANGE HEAT STORAGE EVACUATED SOLAR COLLECTOR TUBE

为提高相变蓄热真空太阳能集热器的热性能,针对相变填充材料固态时传热性能低、集热管释热效率低等问题,提出一种新型的带有一体化轴向双翼翅片结构的U型管式相变蓄热真空太阳集热管结构,分析在不同质量流量运行工况下翅片主要结构参数对集热管释热和蓄热性能的影响,得出最佳的翅片结构参数,并与两种传统结构的集热管性能进行对比分析。结果表明:对于外径为58 mm的玻璃真空太阳集热管,采用复合相变填充材料Na_(2)SO_(4)·10H_(2)O+石墨(质量比92%∶8%)时,释热和蓄热性能最佳的翅片结构参数是翅片长度/翅片夹角为17 mm/60°;该最佳翅片结构能显著强化集热管内的传热性能,使集热管内相变填充材料的温度均匀性更好,使新型U型管式相变蓄热真空太阳集热管相较于圆翅片、无翅片结构形式的集热管,释热量最高可分别提高6.4%和112.6%,释热效率最高可分别提高6.4%和117.4%。

To enhance the thermal performance of phase change heat storage evacuated solar collectors,a new type of U-tubular phase change heat storage evacuated solar collector tube structure with an integrated axial double-wing fin structure is proposed.This design aims to address the issues of low heat transfer performance and low heat release efficiency of the collector tube when the phase change filling material is in a solid state.The influence of the main structural parameters of the fin on the heat release and heat storage performance of the collector tube is analyzed under different mass flow operating conditions,and the optimal fin structure parameters are determined.Furthermore,the performance of collector tubes with two conventional structures is compared and analyzed.The results indicate that,for the all-glass evacuated solar collector tube with an outer diameter of 58 mm,using a composite phase change filling material consisting of Na_(2)SO_(4)·10H_(2)O and graphite(mass ratio 92%:8%),the optimal finned structure parameters,fin length/fin angle,for achieving the best heat release and heat storage performance are determined to be 17 mm/60°.The optimal fin structure significantly improves the heat transfer performance within the collector tube and enhances the temperature uniformity of the phase change filling material.Comparing the collector tube with the round fin and no fin structure,the optimal fin structure in the new U-tubular phase change heat storage evacuated solar collector tube increases the heat release by up to 6.4%and 112.6%and improves the heat release efficiency by up to 6.4%and 117.4%,respectively.