Simulation Study For The Application Of Shaped Molten Salt Composite Thermal Energy Storage Materials In Electrical Heating System

With the constant improvement of the proportion of renewable energy in the entire energy structure,the wind power has been developed rapidly and large installation has been achieved in China.But in recent years,there is a serious phenomenon of wind energy curtailment,resulting in low utilization rate of wind power generation.Meanwhile,the government has issued various policies to phase out small coal-fired furnaces due to the environmental problems such as smog caused by heating in the northern region of China.Therefore,the use of wind power curtailment in place of coal heating is one of the main directions of urban clean heating.This dissertation focuses on the key technologies for the application of latent heat thermal energy storage to local district heating with wind power consumption.It includes the selection rules of composite phase change materials,optimization simulation of tube-type phase change heat storage unit,the coupling relationship of heat storage units.?1?In this dissertation,three kinds of medium-high temperature composite phase change materials were prepared,which include the carrier materials?SiO₂ and MgO?,medium-high temperature phase change materials?nitrate and nitrate?and high conductivity material?graphite?.The micro-encapsulation of the phase change materials are realized by the microstructure of the carrier materials,so that the prepared composite phase change materials can work stably without leakage in the liquid phase.?2?The mathematical model of the tube-type phase change heat storage unit was established.The effects of heat exchanger arrangement,structure,the number of fins and the center distance on the heat transfer performance were studied.The results show that the melting rate of the 60°arranged heat exchanger is faster than that of the 90°arranged heat exchanger,which is related to the turbulent kinetic energy;the heat storage performance of square heat exchanger is better than that of the circular heat exchanger.Compared with the heat storage heat exchanger without fins,the heat storage performance of the heat storage heat exchanger is improved significantly,and the melting time of phase change material is shortened by 66%.Within a certain range,the pressure drop increases as the center distance decreases,but the heat storage performance increases accordingly.?3?The coupling relationship between the heat storage unit and the heating system is discussed.The mathematical model of the two wind power heat storage systems are established,and establish a simple experiment to verify the simulation model.The simulation results show that the melting time of the phase change material decreases as the heating temperature increases.Simply increasing the thickness does not enhance the heat storage effect.Within a certain range,the thickness of the phase-change material layer should be moderate.Results also show that,the PCM melting time is shortened with the increase of Re,but the pressure drop caused by the increase of Re is large.