Research On Heat Transfer Enhancement Based On S-CO₂ Solar Power Generation

Supercritical carbon dioxide?S-CO₂?solar thermal power generation has been widely studied in recent years because of its high efficiency and simple cycle structure.Solar energy has the disadvantages of intermittent and unstable,which can be solved by latent heat storage system.At present,most of the researches on regenerators at home and abroad are sensible heat storage and regenerators using low-temperature PCM,and there are few studies on high-temperature regenerators used for S-CO₂ solar thermal power generation.In this paper,under the support of the National Natural Science Foundation of China?NO.51906228?,the heat transfer research on heat storage based on S-CO₂ solar thermal power generation was carried out.The main research contents are as follows:?1?Taking sodium chloride molten salt as the research object,the thermal conductivity,viscosity,heat capacity and other physical parameters were calculated by molecular dynamics methods,and compared with literature values to verify the correctness of molecular dynamics methods and procedures.?2?The heat exchange performance of sodium chloride is enhanced by adding nano-copper particles.The molecular dynamics method is used to calculate when the mass fraction of nano-copper is 2.01%,the thermal conductivity of the composite phase change material at each temperature increases compared to pure sodium chloride about20%.Viscosity increased slightly within 5%,and the specific heat increased by 10.36%.The change of thermal conductivity and viscosity of the composite phase change material was calculated when the temperature was 1100K and the nano-copper mass fractions were 0.5%,1.16%,1.8%,2.45%,and 3.07%.The thermal conductivity and viscosity of the composite phase change materials have increased correspondingly,but the rate of increase in thermal conductivity is getting lower and lower.?3?The heat storage characteristics of the phase change material and S-CO₂ phase change were simulated,the effect of the addition of nanoparticles on the melting rate of the composite phase change material was analyzed,and the inlet direction,inlet speed and heat exchange temperature difference were analyzed.The effect of the heat storage rate of the regenerator has been found to enter from below to reduce the heat transfer time.The higher the inlet speed,the stronger the fluid disturbance,the more significant the heat transfer effect,and the greater the heat transfer temperature difference,the faster the heat transfer rate.?4?Optimize the structure of the regenerator,numerically simulate the difference between the heat transfer process of the bellows and the smooth tube,and analyze the effect of adding fins on the heat transfer process.The results show that the bellows and fins can effectively enhance heat transfer.The research conclusion of this paper has certain reference significance for the research of S-CO₂ solar thermal power storage.