| In order to ensure the sustainable growth of human social economic and to meet the urgent requirements of environmental protection,the development and utilization of renewable energy is the most effective way to solve current problems.Solar energy has many advantages,such as huge reserves,wide distribution,clean and free of pollution,and so on.It is an ideal renewable energy source.Due to the high cost of solar photovoltaic power generation and the pollution of battery,the large-scale construction and application were limited.Solar thermal power generation can be large-scale constructed,which has the heat storage system and has the more competitive than solar photovoltaic power generation.The choice of heat transfer and storage medium is a vital link in the solar thermal power generation technology.The appropriate heat transfer and storage medium can not only reduce the cost of power generation,but also can improve the efficiency of solar thermal power generation system.The molten salt has a lot of advantages,such as low cost,high temperature,good safety,latent heat,high energy density,and good thermal stability,so it stands out in a large number of phase change thermal storage materials.So far,most of the heat storage materials used in the field of solar thermal power generation are nitrate.But the maximum use temperature can only reach 600℃.The temperature Range of chloride is broad,which can make up for the deficiency of nitrate,therefore,this paper choose chloride salt as the basic material and do experimental study on the mixed heat storage phase change material.In this paper,eighteen kinds of binary mixed chloride and thirty-six kinds of ternary mixed chloride salt were prepared and mixed by the static melting method at the temperature of 600℃.The experimental results show that the melting point of eight kinds of binary mixed chloride which can melt is about 340℃,and twenty-nine kinds of ternary mixed chloride salt which have a typical single melting peak is 350℃.The latent heat of potassium chloridelithium chloride(10%-90%)is the largest in eight kinds of binary mixed chloride.When the mass ratio of potassium chloride and lithium chloride was similar,the latent heat of mixed molten salt is larger.The more phase difference between A and B,the smaller latent heat is.The latent heat of sodium chloride-Potassium chloride-lithium chloride(10%-50%-40%)is the largest in twenty-nine kinds of ternary mixed chloride salt.With the increase of the mass fraction of sodium chloride,the phase change latent heat of the mixed molten salts showed a gradually decreasing trend in general.In this paper,five numbers of heating and cooling cycle experiments were carried out to study the thermal stability and freezing point of two kinds of molten salt,which have the largest latent heat.The results display that the initial measured value of melting point is higher than the later four numbers value,and the last four curves are almost coincident but the first one.The two kinds of molten salt have good thermal stability.The freezing point temperature of the two kinds of molten salt samples is lower than that of the melting point,so they can reduce the possibility of freezing and plugging the pipeline system.Finally,the corrosion experiments were carried out to study the corrosive characteristics of two kinds of molten salt.We put the two kinds of stainless steel which are 304 and 316 L in chlorine salt.It is found that the corrosion of two kinds of stainless steel sheets in two kinds of mixed chloride molten salt is more serious,and the corrosion degree increases with the increase of corrosion environment temperature.The corrosion resistance of 316 L steel sheet is weaker than 304 steel in the two mixed chlorine salt. |
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