Processing Compressed Expanded Natural Graphite for Phase Change Material Composites  

作　　者：Alexander BULK Adewale ODUKOMAIYA Ethan SIMMONS Jason WOODS 

机构地区：[1]National Renewable Energy Laboratory,15013 Denver West Parkway,Golden,CO 80401,USA

出　　处：《Journal of Thermal Science》2023年第3期1213-1226,共14页热科学学报（英文版）

基　　金：Funding provided by U.S.Department of Energy Office of Energy Efficiency;Renewable Energy Building Technologies Office。

摘　　要：Phase change materials(PCMs)are used in various thermal energy storage applications but are limited by their low thermal conductivity.One method to increase conductivity involves impregnating organic PCMs into highly porous conductive matrix materials.Of these materials,compressed expanded natural graphite(CENG)matrices have received the most attention.Despite this attention,the effect that CENG processing has on PCM saturation and overall matrix thermal conductivity has not been fully investigated.Therefore,the effect of the heat treatment process used to expand intercalated graphite flakes is evaluated here.Higher heat treatment temperatures yielded higher saturation rates and overall saturation at similar matrix porosities.For example,increasing temperature from 300℃to 700℃resulted in approximately 60%-70%increase in pore saturation after 100 minutes of soaking.The exposure time to heat treatment had less of an effect on PCM saturation.The exposure time had negligible effect above 30 min and above 500℃heating temperatures.However,because the expanded graphite was found to oxidize around 700℃,the use of longer exposure time in manufacturing applications can be beneficial if a shortened impregnation time is needed.Heat treatment conditions did not impact thermal conductivity.The composite latent heat of fusion was also reduced approximately proportionally to the PCM mass fraction.A local maximum in axial thermal conductivity was observed at around 83%porosity,which is similar to previous studies.The observed conductivity at this maximum was a factor of 81 times greater than the conductivity of the PCM.

关 键 词：phase change materials thermal energy storage compressed expanded natural graphite thermal conductivity enhancement porous material sorptivity composite matrix 

分 类 号：TB332[一般工业技术—材料科学与工程]