Study On The Phase Change Heat Storage Characteristics Of Mg-Ca-Sn-Bi Alloy

There is a close relationship between energy and social-economic development.Economic development has consumed a lot of non renewable resources,and new energy has become a new opportunity for all countries in the world to seek development.At present,solar energy is the most widely used new energy source,which has a wide range of sources,clean and pollution-free,and has high value of utilization.However,the uneven distribution of solar energy is a major challenge because of the climate and season,which greatly limits the use of solar resources for human beings.So it has been a hot topic for various countries to research the suitable solar storage methods and storage media.Based on previous studies,this thesis first attenmps to design and prepare the Mg-Ca-Sn-Bi series alloys as phase change heat storage materials.Then a drainage method is used to measure the density of alloys,a differential scanning calorimeter is used for measuring the phase transition temperature and latent heat,and the X-ray diffractomer and electro-probe microanalyzer are used for the analysis of these alloy's microstructure.And the influence of adding Sn and Bi elements on the heat storage properties and microstructure of Mg-Ca alloy is discussed.Finally,the compatibility between heat storage alloy and Q235 carbon steel and 304 stainless steel are studied.The main results are as follows:The density of Mg-15Ca alloy is 1.668 g·cm^-3.After adding 5%,15%and 30%Sn elements,the density of the alloy is 1.695,1.765,1.996 and 2.304 g·cm^-3,respectively.And the density of Mg-20Ca-40Bi alloy and Mg-15Ca-5Sn-35Bi alloy is2.304 and 1.719 g·cm^-3,respectively.The microstructure of Mg-15Ca alloy is composed of?-Mg phase+??-Mg+CaMg₂?phase.The former is the matrix structure,and the latter is a eutectic tissue.The microstructure of Mg-15Ca-xSn alloy add phases of Mg₂Sn and CaMgSn.The microstructure of Mg-20Ca-40Bi alloy add phases of Mg₃Bi₂ and CaMg₂Bi₂.And the microstructure of Mg-15Ca-5Sn-35Bi alloy add phases of Mg₂Sn and Mg₃Bi₂.The phase-transition temperature range of Mg-15Ca alloy is 515.55⁵18.20?,the latent heat is 86.81J/g;After adding Sn element by 5%,15%and 30%,the temperaturerangeofalloysare517.37⁵22.74?,516.21⁵19.67?,515.69⁵19.28?,respectively.And the latent heat are 195.10,104.90,123.20 J/g,respectively.The phase transition temperature range of Mg-20Ca-40Bi and Mg-15Ca-5Sn-35Bi alloys are 516.26⁵19.71?and 516.22⁵21.20?,the latent heat are 169.1 and 183.90J/g,respectively.Then selecting Mg-15Ca-5Sn alloy as the heat storage material,Q235 steel and304 stainless steel as the material of the storage container,the compatibility tests between them have been taken under the condition of the high temperature of 600?.The results show that two kinds of steel have different degrees of corrosion,of which304 stainless steel have better corrosion resistance.So,it is a better reservoir vessel materials.