Experiment And Mechanism Study On Thermal Conductivity Of MWCNTs-Solar Salt

With the increasing consumption of fossil fuels,the non-renewable fossil resources are facing serious problems.The utilization of the renewable resources as one kind of abundant renewable energy,solar power is a very promising new energy power generation technology.The solar energy can be converted to electric energy in two ways: photovoltaic power generation and Concentrating Solar Power(CSP).The difference of CSP generation from the photovoltaic power generation is that photo-thermal power generation systems are equipped with energy storage component,which make it suitable for the load regulation.CSP is one way to utilize the solar energy at high temperature.The collected solar energy is used to heat the water and produce the steam to drive the turbine to generate power.The CSP technology involved different energy conversions.The rational use of thermal energy is the key technical issue for CSP.In the CSP generation system,there are many restrictions for the selection of the materials for the heat transfer and storage,such as low corrosion,high heat capacity and stability,high thermal conductivity,and its reusability.As one promising material for heat transfer and storage,molten salt has been paid extensive attention in the industrial use.On the basis of the current research,this paper will explore the feasibility of the molten salt to be used in CSP as heat storage mediaIn this paper,MWCNTs(Multi-Wall Carbon Nano-Tube)were added into the solar salt.The formation of clusters and the liquid film layer on the surface of the cluster promoted a substantial increase of thermal properties of the new mixture.Therefore,a new type of heat storage material,MWCNTs-solar salt composite material,namely Multi Walled Carbon Nanotubes Salt composite material,is proposed creatively.At the same time,the calculation model of thermal conductivity was established.The MWCNTs-solar salt composite was prepared by hand and the thermal properties including the thermal conductivity were measured to verify the accuracy of the thermal conductivity calculation model.The theory and mechanism of thermal conductivity enhancement is also analyzed in this paper.The calculation model of thermal conductivity is reduced including micro convection model and particle diffusion correction factor.The effects of agglomeration,particle distribution,micro-convection due to Brownian motion including the influence of temperature change are also considered in this model.The thermal conductivity of the molten salt composite made in this study was measured in melting state,and compared with that calculated with the calculation model.The results show that the thermal conductivity can be well predicted with this calculation model.The maximum increase of thermal conductivity can be up to 49.1% due to the addition of the multi-wall nano-tubes.the average error of the theoretical value with the calculation model and the measured value is no more than 5.79%,lower 9.57% than the primary calculation model.