The Preparation And Performance Of Composite Phase Change Materials-Multicomponent Eutectic Hydrated Salt Phase Change Material And Porous Matrix

This paper prepared a novel Na₂CO₃·10H₂O-Na₂HPO₄·12H₂O EHS and studied its heat storage performance.the supercooling problem was optimized by response surface method.according to the optimization results,the Na₂CO₃·10H₂O-Na₂SO₄·10H₂O-Na₂HPO₄·12H₂O EHS phase transition system was prepared and combined with porous matrix to explore the application of the ternary system in practice.finally,the crystalline hydrated salt Ba?OH?₂·8H₂O with the highest latent heat of phase transition in the low temperature regions was optimized by adding nucleating agent.The main results are as follows:?1?Na₂CO₃·10H₂O and Na₂HPO₄·12H₂O two kinds of hydrated salt can be prepared by melt-mixing method binary EHS..The mass ratio of Na₂CO₃·10H₂O to Na₂HPO₄·12H₂O is the best mass ratio at 4:6,and the phase transition temperature is 24.1?,the latent heat of phase transition is 214.4 J/g,and the supercooling degree is 15.6?.the response surface method is used to optimize 40%Na₂CO₃·10H₂O-60%Na₂HPO₄·12H₂O binary EHS,reduce the EHS undercooling.The amount of CMC?SiO₂ and Na₂SO₄·10H₂O was three independent variables to reduce the undercooling degree.According to the designed experiment scheme,the undercooling degree of each samples was calculated by step cooling curve method,simulated modeling,and the secondary regression model was selected to study the problem.The reliability of the model was tested according to the analysis of variance.The results show that the optimum dosage is 0.5-1.5%for SiO₂,7.5-26%for Na₂SO₄·10H₂O and0.5%for thickener CMC.?2?The 11%Na₂CO₃·10H₂O-11%Na₂SO₄·10H₂O-78%Na₂HPO₄·12H₂O EHS phase transition system was prepared by adding Na₂SO₄·10H₂O to the binar phase transition system.The phase transition temperature was 13.1?,and the latent heat of phase transition 203 J/g,almost eliminated the undercooling.The EHS phase change heat storage material shows no phase separation after 50 freeze-thaw cycles.The DSC curve shows that the crystallization temperature decreases to 12.6?and the latent heat of phase change decreases to 196 J/g after50 freeze-thaw cycles,indicating that the ternary EHS phase change material has high cycle stability.but the evaporation of bound water leads to poor thermal cycling stability.The ternary EHS/nickel foam composite phase change material was prepared by vacuum impregnation method to solve the problem of decreasing heat storage performance caused by EHS water evaporation.The cycling stability of the composite phase change material was investigated by step cooling curve method.The supercooling degree after 50 freeze-thaw cycles increased by 1.5?showing good cycle stability,and the thermal conductivity of the material increased the heat storage and discharge rate of the material.?3?The undercooling of Ba?OH?₂·8H₂O was effectively reduced by adding Na₂HPO₄·12H₂O?Na₂SO₄·10H₂O as a nucleating agent to Ba?OH?₂·8H₂O.the addition of Na₂HPO₄·12H₂O as a nucleating agent to Ba?OH?₂·8H₂O has the best effect of promoting nucleation in the range of 0.3 wt%to 1.0.the addition of Na₂SO₄·10H₂O as nucleating agent to Ba?OH?₂·8H₂O with 1.0 wt%,showed the best undercooling inhibition for Ba?OH?₂·8H₂O.Na₂HPO₄·12H₂O better than Na₂SO₄·10H₂O.Na₂HPO₄·12H₂O as nucleating agent can reduce the undercooling of modified Ba?OH?₂·8H₂O to less than 3?with a minimal addition amount?0.3 wt%-1.0wt%?.Adding 0.3wt%Na₂HPO₄·12H₂O of Ba?OH?₂·8H₂O has excellent heat storage performance in the application of recovering industrial high temperature exhaust gas.