Abstract: 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 Na₂SO₄·10H₂O 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.