The Modification Of Multivariate Carbonate Phase Change Thermal Storage Materials

Solar thermal power technology is the main energy research in the future.But its lack of continuity in time and space makes the study of heat storage particularly critical. Based on the investigations of phase change thermal storage materials of inorganic salts, added different amounts and different types nitrates, carbonates and high conductivity materials into K2CO3-Na2CO3-Li2CO3. Then chosen the best multi-carbonate and studied its compatibility with 316 L stainless steel and 304 stainless steel at 600 ?. Used DSC, TG,EPMA and other test methods to focus on the latent heat of diverse carbonate, the phase transition temperature, decomposition temperature, specific heat capacity and corrosive.Through analyzing samples' DSC curves with adding 10%, 20% and 30% nitrate and carbonate, it was found that carbonate as an additive could do a better eutectic, latent heat and reduce the melting point of the base salt. The type and amount of additives had an impact on the phase change latent heat, and with the increase in the content, the latent heat had been reduced. Compared and analysized the phase change latent heat and phase change temperature with inorganic salt from the lattice energy and electrostatic force.Preferred the better multivariate mixed inorganic salts tested the decoposition piont by TG analysis, got the different samples' temperature range. It was found that when barium carbonate, strontium carbonate, manganese carbonate was an additive,the base salt decomposition point had been increased obviously. The highest point of adding 10%BaCO3,10%SrCO3, and 20%SrCO3 had reached to 820?. Based on this calculated the Gibbs free energy change of carbonate diverse chemical reactions may occur at high temperatures. Analyzed the main factors affecting the instability of the high temperature molten salt.Added 10%,20% and 30% BaCO3 into based salt. Though analyzing the specific heat capacity curve, it could be found that the heat capacity curve was rising slowly from 100? to 280?. The average of the heat capacity was reduced with the increasing of additives.Through thermal conductivity and DSC, graphite, granular graphite and carbon fiber decreased the latent heat of inorganic salt and improved the thermal conductivity. Added expanded graphite could achieve to 4.04W/m·K.Studied the compatibility of based salts at 600? molten state with 316 L stainless steel and 304 stainless steel by static corrosion test method. Through optical microscopy, scanning electron probe on the sample after etching 192 h, two kind of steels were just slight corrosion. There was neither pits or bumps nor accumulation of corrosion products on the corrosion layer. XRD analysis showed that only a weak Li and O elements were in erosion layer, the rest were mainly austerity phase and marten-site phase.By analyzing the kinetics of stainless steel etching showed that the based salts K2CO3-Na2CO3-Li2CO3-10%BaCO3 were better compatibility with 316 L stainless steel and 304 stainless steel.