Study On The Supercooling And Thermal Cycling Of Salt-hydrates

The reduction of the thickness of electronic devices has become prevailing.Adding heat storage module can enhance its heat dissipation ability.The materials in the module should have the characteristics of stable operation,strong heat storage capacity and low cost.In order to meet those requirements,two hydrated salts are selected for investigation in this thesis:Na₂HPO₄·12H₂O and CH₃COONa·3H₂O.The disadvantages of Na₂HPO₄·12H₂O and CH₃COONa·3H₂O as pure materials in practical application are analyzed:supercooling and phase separation,and the causes are analyzed.In order to solve this problem,firstly,nucleating agent and thickening agent was used to modify the materials.In addition,the supercooling of the Na₂HPO₄·12H₂O and CH₃COONa·3H₂O’s mixture was studied.Finally,a long time thermal cycling was carried out to study the stability of the hydrated salt samples.The main conclusions of this paper are as follows.（1）Pure Na₂HPO₄·12H₂O or CH₃COONa·3H₂O as the main material of the phase change material are unstable.When one kind of hydrated salt is used as the main research object with added thickener and nucleating agent,the mixed liquid failed to work after 10^th of thermal cycling.It can’t be reused as heat storage in the subsequent heating process.（2）The mixture of the two kinds of hydrated salt materials is studied.The supercooling of the mixture is improved than that of a single hydrated salt.The addition of a suitable nucleating agent and thickener can effectively suppress the supercooling tendency of the system based on the mixture of Na₂HPO₄·12H₂O and CH₃COONa·3H₂O.Experimental results show that the material can be stable after 1000 times of thermal cycling.