Preparation And Properties Of A Shape Stabilized Composite Phase Change Material Of Inorganic Hydrate/Diatomite

The inorganic hydrated salt phase change materials is the most widely used type of phase change materials at medium-low temperature,which has the advantages of high energy storage density,high latent heat value,high thermal conductivity than organic phase change materials.However,inorganic hydrated salt phase change materials also has such problems as supercooling,phase separation and leak.In this study,based on the existing problems,we used diatomite composite porous structure to adsorb inorganic hydrated salt prepare the shape-stabilized composite PCM.In addition,our study also capitalized on reduce the supercooling degree and increase the thermal conductivity of the shape-stabilized composite PCM in order to prepared shape-stabilized composite PCM with low supercooling,high thermal conductivity and excellent chemical and thermal stability.SAT/diatomite shape-stabilized composite phase change material,SSD/diatomite shape-stabilized composite phase change material and CCH/diatomite shape-stabilized composite phase change material were prepared by impregnation method.The SAT,SSD and CCH were uniformly adsorbed on the internal and external surface of diatomite.The maximum adsorption amount of SAT,SSD and CCH were 63%,63% and 65%,respectively.We chose dodecahydrate sodium phosphate(DSP),borax(DTD)and strontium chloride hexahydrate(SCH)respectively for the SAT,SSD and CCH nucleating agent.Nucleating agent heterogeneous heterogeneous nucleation mechanism is used to improved crystallization rate of hydrated salt and reduce supercooling degree.The results showed that adding 2% of the DSP,SAT/diatomite composite phase change materials of supercooling degree reduced to 0.6?;adding 1% of the DTD,SSD/diatomite composite phase change materials of supercooling degree reduced to0?;adding 1% of the SCH,CCH/diatomite composite phase change materials of supercooling degree reduced to 0.3?.We added graphite to the composite phase change materials,reducing the thermal resistance of the composite phase change materials,and increasing the thermal conductivity of the composites.The results showed that after adding 10%graphite,the thermal conductivity of SAT/composite phase change materials increasedfrom 0.78W/(m·K)to 0.78W/(m·K),the thermal conductivity of SSD/composite phase change materials increased from 0.45W/(m·K)to 0.85W/(m·K),and the thermal conductivity of CCH/composite phase change materials increased from 0.56W/(m·K)to 0.95W/(m·K).After adding nucleating agent and graphite,the phase change material in SAT/diatomite shape-stabilized composite phase change material melting temperature is 57.8?,melting enthalpy is 149.4J/g,solidification temperature is 56.5?,solidification enthalpy is 130.5J/g;the phase change material in SSD/diatomite shape-stabilized composite phase material melting temperature is 32.1?,melting enthalpy is 135.1J/g,solidification temperature is 31.7?,solidification enthalpy is112.9 J/g;the phase change material in CCH/diatomite shape-stabilized composite phase change material melting temperature is 29.1?,melting enthalpy is 110.1J/g,solidification temperature is 28.8?,solidification enthalpy is 108.7J/g.All diatomite shape-stabilized composite phase change material have excellent morphological stability,chemical stability and thermal stability.After 200 fusion-solidified heat cycles,their chemical properties do not change,and the melting enthalpy was reduced by 3.4%,1.3% and 0.5%,respectively;solidification enthalpy decrease by 3.9%,1.5% and 3.9%,respectively.They all have excellent thermal cycling stability.