Study On Heat Transfer Of Supercritical Carbon Dioxide In Spiral Tube

The issue of efficient energy utilization in today’s society has become a hot research topic.Traditional energy is gradually eliminated due to its low efficiency and large energy consumption.The use of new energy has become a trend.Supercritical CO₂ is widely used in related new heat exchangers because of its high heat transfer characteristics and low environmental pollution.In this paper,the spiral tube is used as the physical model for simulation research,and the method of numerical simulation is used to conduct scientific research on the heat transfer characteristics of supercritical CO₂ in the tube.The final results obtained can provide reference for the application of supercritical fluid in practical work.First of all,this article introduces the definition of supercritical fluid and its advantages as a new energy source and sorts out the results of current research in this direction at home and abroad.Then,under the same wall temperature heating standard,the flow process and heat transfer changes of supercritical CO₂ in the tube were simulated.Through Ansys Fluent software,the applicability of the two equations of RNGκ-εwas verified,and the temperature,velocity and relative density of supercritical CO₂ during the whole process of partial convective heat transfer of the spiral tube were obtained.And the change trend of its temperature,velocity and heat exchange capacity when the fluid flows in the tube.The factors affecting the heat transfer of supercritical CO₂ in the spiral tube are discussed,such as centripetal force,buoyancy force,and the fluid’s drastically changing thermophysical properties.By controlling the flow resistance of the pipeline and the temperature of the boundary layer,the heat transfer and deterioration coefficient of the heat convection part in the spiral tube are analyzed.Research data shows that the risk of centripetal force propagation exists in the whole process of heat transfer to extensive flow.When the radial angleφ≤1080°,the h on the bottom busbar is larger,and the h on the paraxial busbar is the smallest and reaches the maximum first.The maximum value of the local convective heat transfer coefficient increases slowly with the increase of pipe flow resistance.As the surface temperature increases,it gradually decreases.Finally,through the Fluent software,the heat transfer performance of spiral tubes of different structural sizes was analyzed,and the influence of the parameter changes of spiral tubes of different structures on the deterioration of heat transfer was analyzed;The effect of weightlessness on the thermal conductivity of supercritical CO₂.Research data shows that gravity has little effect on the heat conduction and deterioration of supercritical CO₂ in the spiral tube.Under the standard of ensuring that the main parameters of other structures in the spiral tube are the same,as the diameter of the spiral tube expands,the secondary flow caused by centripetal force and buoyancy force becomes weaker,and the heat transfer coefficient decreases.When the pitch is less than 60mm,the change in pitch will not easily deteriorate the heat transfer effect.But when the pitch is increased to90mm,the heat transfer coefficient will drop significantly.