Thermal Storage Characteristics And Heat Transfer Enhancement Of Ternary Chloride Molten Salt

The phase change heat storage technology has advantages such as large energy storage density,low cost,and approximative isothermal process of storage/discharge process,which can effectively solve the shortcomings of intermittent and non-stability in solar energy heat utilization.The field of solar thermal power generation has a very broad market potential and application value.Molten salt has become one of the preferred materials for thermal energy storage and conversion technology due to its outstanding thermal transport properties and economic efficiency.However,the low thermal conductivity of the phase change material used and the poor heat transfer performance during the phase change process have limited its large-scale application.At present,many scholars at home and abroad have conducted experiments or numerical simulations on the enhanced heat transfer methods of subsurface heat storage,but there are still major difficulties in the analysis of the heat transfer mechanism in the phase change of complex systems,and subsurface heat storage.There are fewer reports on the structural design and numerical studies of the device.Based on this,in this paper,ternary chlorinated molten salt is taken as the research object,combined with experimental measurement and numerical calculation,and the research work is carried out from the aspects of material selection,preparation,test characterization,and design of thermal storage unit.The typical enhanced heat transfer method improves the heat storage rate of submersible heat storage,as follows:The ternary eutectic chloride salt with higher latent heat of phase change and suitable melting point was selected as the phase change material.The pure salt was prepared by high temperature water-solubilizing and dry-drying method.The thermal properties of the met chlorinated salt was obtained by DSC-TG,LFA and other thermal physical property analysis methods.The ternary chloride and ZnO,Al₂O₃ and CuO nanocomposite phase change materials with mass fraction of 0.7% were prepared by a two-step method.The microstructure of the composites was characterized by SEM.It was found that the high thermal conductivity nanoparticles could be doped Significant composite materials increase the thermal diffusivity.The enthalpy-porosity model in the Fluent software was used to study the phase change thermal storage characteristics of molten salt in two-dimensional square cavity and round tube.The intensification of molten salt phase change and heat release after addition of metal fins and porous metal foam copper was investigated.Thermal effects,based on the phase change heat storage characteristics,numerically studied the effect of the flow state in the heat transfer tubes inside the three-dimensional pipe-type heat storage unit on the heat storage process,and found that with the increase of the Reynolds number,the enhancement of the disturbance can be significantly enhanced.Heat,reduce heat storage time.A shell-and-tube submersible heat storage unit was designed to further explore the effect of the heat storage tube bundle arrangement on the heat storage process.The results show that the heat transfer effect is improved by the turbulence intensity and temperature gradient of the flow field.The research results of this paper have certain reference value for the design of submersible heat storage system in solar thermal power station.