Preparation And Thermal Conductivity Research Of Binary Organic Composite Phase Change Heat Storage Materials

In recent years,as the pace of life continues to accelerate and the concept of healthy eating continues to infiltrate,people’s food requirements for food are constantly increasing.The problems of health,environmental pollution and energy waste brought by traditional thermal insulation packaging make it necessary to seek a new energy source with high economic,environmental protection and high utilization rate to become an important issue in solving energy problems today.The phase change material has high energy storage density,stable performance and high cost performance,but its phase transition temperature is single,and its fluidity and low heat transfer rate limit its application.The shaped phase change material consisting of phase change heat storage medium and collective material can not change the phase transition material without macroscopic flow,but can not change the characteristics of single phase transition temperature and poor thermal conductivity.To overcome the above shortcomings,Preparation of composite and thermally conductive enhanced phase change thermal storage materials to extend the application of phase change materials.The specific research contents are as follows:(1)According to the second law of thermodynamics and phase equilibrium theory,the phase change temperature and latent heat of the cetyl alcohol,stearyl alcohol,lauric acid,myristic acid,six phase change materials of palmitic acid and stearic acid were theoretically predicted,and the cetyl alcohol/octadecyl alcohol and stearyl alcohol/palmitic acid and octadecyl alcohol/stearic acid mixed group,which meet the temperature and latent heat requirements were selected,further experiments near the theoretical ratio.The composite phase change material of octadecyl alcohol/stearic acid was prepared at a mass ratio of 66.95:33.05,has good thermal stability,whiche with the phase change temperature and latent heat of 55.47 ℃and 221.3 J/g.(2)The thermally conductive enhanced composite phase change thermal storage material was prepared with octadecyl alcohol/stearic acid as phase change material,expanded graphite as porous substrate,and nano zinc oxide/Micron copper as hybrid high thermal conductivity filler.By characterizing its morphology,chemical structure,thermal properties and thermal conductivity,the results show that phase change temperature and latent heat of composites are 55.38℃ and 195.4J/g,respectively,the thermal decomposition temperature is above 200℃,the thermal conductivity and heat storing and releasing efficiency were increased.After repeated 300 thermal cycles,the composite still shows good thermal stability.(3)The thermally conductive enhanced phase change microcapsules are prepared by in-situ polymerization,with the stearic acid-Octadecyl alcohol eutectic composite phase change materials as core material,UF resin modified by melamine as wall material and MWCNTs-NH2 as highly thermally conductive filler.The results show that the amino-modified MWCNTs have good dispersibility in the solution;The compounded emulsifiers of SDBS and Triton X-100 make the surface morphology of the microcapsules smoother and smoother;The addition of MWCNTs with the mass ratio of 0.25%,0.5% and 0.1% make the microcapsule’s thermal conductivity reach 0.224W(m·K),which increased by 62%(55°C),the coating rate increased by 5.5%,the particle size is more uniform and the thermal stability is significantly improved.(4)The application test of the heat-conductive enhanced composite phase change thermal storage material and the thermally conductive enhanced composite phase change thermal storage microcapsule in the food insulated container was carried out.The results show that the thermal conductivity enhanced phase change thermal storage material is applied.In the EPS incubator,the incubation time of the incubator with the nano/micron thermally conductive enhanced composite phase change thermal storage material increased by 2 h compared with the control group.The phase change heat storage microcapsules after adding the thermal fluid are used in the temperature control container of the catering package,the time required for the temperature to be lowered from 100 ° C to 60 ° C is 1 h,and the temperature can be maintained at about 40° C ~60 ° C for 3 h,and the temperature is maintained.Above 36 ° C for 6.5 h.It can be seen that the thermally conductive enhanced phase change material plays an important temperature control role in the short-term temperature control of the heat preservation container.