Research On Preparation And Thermal Performance Of Composite Heat Storage PCMS With ENG And MoLten SaLts

Facing with the the growing depletion of Coal,Petroleum,Gas and other energystatus,how to improve the energy efficiency has become the major question that manyscientists now focus on.Because of the solar energy with the advantage ofinexhaustible,It is widely used in production and life，But the application is constraint,because of the discontinuities.So latent heat energy storage is raised. It is a newenvironment-friendly energy-saving technology to use phase change materials forlatent heat energy storage.In order to solve the problems of the storage、transportationand the low thermal conducitivity, The porous graphite could be combined with phasechange materials to prepare the novel shape-stabilized phase change materials.Firstly, expanded graphite was prepared by the method of chemical oxidation,nitrate as the oxidant, glacial acetic acid、formic acid as the insertion in this process.The best process conditions was obtained: The results show that swelling volume ofgraphite can reach246.5mL/g in600℃while the weight of the Scales graphite is10gand the volume ratio of ingredients （glacial acetic acid：formic acid：nitrate）2：3：4, in the reaction time of45min, and the reaction temperature is20℃by theorthogonal test. The insertions were analyed and measured by X-ray diffraction,themorphology of the expanded graphite was observed by SEM, the composition ofnaturaL flake graphite is by EDS element anaLysis. the results show there are twomain elements in the natural flake graphite,such as carbon and oxygen element; theinserti-ons has inserted between graphite layers and the structure of the morphologyof the expanded graphite is loose and porous.Secondly，The phase change of temperature of different ratio potassium nitrateand sodium nitrate is calculated by the formula of schrooder.The results show that thephase change of temperature which is calculated coincide with the experiment of thecooling cure,and make sure that the phase change of temperature and relative size oflatent heat about different proportions of mixed Nitrate Solution,at last also make sureBinary Systems to achieve eutectic composition ratio is the equal-mole mixture.AndMoore’s eutectic nitrate as the temperature of the heat storage medium range below450℃.When the temperature is higher than600℃and Heat preservation12hours,mass loss is of0.4%. The experiment of TG-DSC shows that when Eutectic Salt isheated,there are two phase changes:one is solid-solid change, the temperature of phase change is117.5℃-132℃,the latent heat is33.34J/g.two is solid–liquid change,the temperature of phase change is219.5℃-227℃,the latent heat is116.6J/g.Underthe working temperature for400℃，There is no new substance for the content ofpotassium nitrate and sodium nitrate.Thirdly,There are five kinds of moLding pressure:two millon palmer、four milonpalmer、six millon palmer、eight millon palmer、twelve millon palmer.Only under twomillon palmer,the recombination rate of shape-stabilized phase change materials isrelative max,and that which leakage of phase change materials is relative min.In thesame molding pressure（two millon palmer）, different graphite content（47%、37%、30%、26.5%、23%）,It which leakage of phase change materials has nothing to do withthe quantity of phase change materials. It is proved by SEM that porosity withinthe“salt dominant” layer, which mainly depends on salt crystals packing, andconsequently, on salt crystals-size distribution. This porosity is directly accessible tothe liquid phase during salt melting.It is also proved by SEM that the porosity withinthe“graphite dominant” layer, which depends on the graphite amount added as wellas on the strength reached during compression. This porosity is rareLy accessibLe tothe salt which liquid state. The experiment of XRD shows that: Through the14timescooling cycle，the phase and composition for composite material are most of KNO₃（15.67%）、NaNO₃（8.35%）、C（85.91%） and a small amount of K₂CO₃（1.25%）;theexperiment of TG-DSC shows that: Solid-solid phase transition temperature ofshape-stabilized phase change materials is118.4℃，the latent heat is24.42J/g;theaddition of the expanded graphite did not change the phase change of temperature ofthe eutectic salt,but it makes that latent heat of phase change reduces.