Preparation And Thermal Properties Of Phase Change Nanofluid With Addition Of Nanoparticle Glauber's Nitrogen

Glauber's salt-based phase change materials(PCMs)are inorganic hydrated salt PCMs,which can be used in waste heat recovery,thermal insulation building walls,etc.to improve energy efficiency,reduce energy consumption to a certain extent,and have broad application prospects.However,its existence of subcooling,phase stratification,low heat transfer performance,etc.limit the popularization and application of Glauber's salt PCMs.In the experiment,multi-walled carbon nanotubes and nano carbon powder were selected as additives,and the mirabilite-based PCMs was prepared into mirabilitebased phase-change nanofluid,so as to reduce the supercooling degree of the mirabilite-based PCMs and reduce the phase stratification.Improve thermal conductivity.Viscosity,as one of the important parameters of rheological properties,affects the efficiency and cost of future engineering applications,so the research on rheological properties is also indispensable.Firstly,the multi-walled carbon nanotubes were modified and the rheological properties,subcooling degree and cycle stability of the Glauber's salt-based PCMs nanofluid were tested.The test results are: when the volume fraction of carboxylated multi-walled carbon nanotubes increases from 0.05% to 0.25% under the conditions of30? and 50?,the viscosity of the Glauber's salt-based phase change nanofluid increases by 73.85% and 69.10% respectively,that is,Glauber's salt The lower the temperature of the base PCMs nanofluid,the greater the effect of the volume fraction change on the viscosity;when the volume fraction is 0.05% and 0.25%,when the temperature rises from 30? to 50?,the viscosity drop of the nanofluid is 39.12%,respectively And 40.78%,that is,the lower the volume fraction,the smaller the effect of temperature changes on the viscosity.The modified multi-walled carbon nanotube mirabilite phase change nanofluid was placed for 30 days,and no phase delamination occurred.The supercooling degree of the mirabilite PCMs nanofluid with 0.25%amide-based multi-walled carbon nanotubes added is 0.13?,and after 100 cycles of cooling and heating,the heat absorption is reduced by 14.4% and the performance consumption is less.The test results of the modification of the nano carbon powder and the rheological and thermal properties of the Glauber's phase change nanofluid show that the lower the temperature of the Glauber's phase change nanofluid,the higher the sensitivity of the viscosity to the volume fraction change;The lower the score,the lower the sensitivity of the viscosity to temperature changes.At 40?,adding 0.25% modified nano-carbon powder mirabilite-based PCMs nanofluid,the thermal conductivity of mirabilite-based PCMs without adding nanoparticles increased by 11.93% on average.According to the H-C model,the dispersion stability of modified nano-carbon powder is better than that of unmodified nano-carbon powder in mirabilite-based phase change nanofluid.The supercooling degree of the mirabilite-based phase change nanofluid with 0.25%volume fraction of the amido-based nanocarbon powder is 0.08?.After 100 freezethaw cycles,the heat absorption of the mirabilite-based PCMs nanofluid is reduced.15%.Compared with the multi-walled carbon nanotube mirabilite PCMs,the degree of subcooling is lower,but the energy storage density loss is relatively larger by 0.6%.Therefore,nanoparticles should be selected according to specific needs.