Phase Change Heat Storage U-finned Tube Vacuum Tube Solar Collector Research On Heat Storage/heat Release Performance

In today’s world,the energy crisis is becoming more and more serious,and the development and utilization of new clean energy is more and more urgent.As the most extensive new energy resource,solar energy has been paid more and more attention by all countries.Solar photovoltaic and photothermal utilization technologies are also gradually mature,and the large-scale development and utilization of photovoltaics and photothermal can effectively alleviate the growing global energy demand.However,due to the discontinuity of solar energy,storing temporarily surplus energy has become a more common response method.For this reason,many scholars have proposed the U-tube phase change thermal storage vacuum tube collector as a form of solar thermal utilization.And many scholars and experts have put forward that the heat transfer performance of the U-tube phase change heat storage vacuum tube collector can be improved by improving the physical properties of the phase change material and changing the fin structure through a lot of research.Firstly,on the basis of comparing research literatures,this paper proposes a new type of phase-change energy storage U-finned tube vacuum tube solar collector structure.Using the numerical simulation method of FLUENT software,the heat release process and the heat transfer performance of the heat storage process of the phase change heat storage vacuum tube collector with different parameters and different operating conditions are studied.The heat storage/heat storage of the collectors with various fin parameters is carried out using indicators such as the outlet temperature of the heat transfer medium T_water,the weighted average temperature of the composite phase change material T_pcm1,the heat release amount Q_waterof the collector,and the heat release efficiencyηof the collector during the heat release process.Heat release performance evaluation.Then,the influence of the fin structure on the heat release performance of the phase change heat storage vacuum tube collector was analyzed in detail,and the change rule of the heat release performance of the vacuum tube collector under the influence of different parameters of fins was obtained,and the best heat release performance was obtained.fin form.The results show that when the fin structure is 17mm/60°（the length of the fin is 17mm and the angle is 60°）,the heat release performance of the evacuated tube collector is the best in various evaluation indicators.This result was verified when the phase change material was Na₂SO₄·10H₂O+graphite,and the mass flow rate of the heat transfer medium inlet was0.010kg/s,0.008kg/s,and 0.006kg/s,respectively.Similarly,when the phase change material was Ba（OH）₂·8H₂O,the heat transfer medium inlet mass flow rate of 0.010kg/s has also been verified.Finally,the heat release performance of the phase change heat storage U-tube collectors with different structures of different phase change materials is compared and analyzed.When the filled phase change materials are all Na₂SO₄·10H₂O+graphite,compared with the17mm/60°fin structure U-tube vacuum tube collector,the traditional circular fin structure and the finless U-tube vacuum tube collector,The results show that when the inlet flow rate is0.010kg/s,0.008kg/s and 0.006kg/s,the heat release performance of the U-tube vacuum tube collector with 17mm/60°fin structure is better than that of the traditional round fins Structural form and finless form.After that,the phase change material was changed to Ba（OH）₂·8H₂O for comparison.Among the three comparative structures,the U-tube vacuum tube collector with 17mm/60°fin structure had the best heat release performance,which was the same as that of the phase change material Na₂SO₄·10H₂O+graphite is the same conclusion.