Study Of Thermophysical And Heat Storage/release Performance For Stearic Acid Form-Stable PCMs

For solving the defects of poor leakage-proof performance,low thermal conductivity,and poor thermal stability of some composite phase change materials,the above problems can be effectively solved by encapsulating the phase change material in a porous solid framework support material.In this paper,sepiolite and mica powder are selected as the supporting material,and stearic acid as the phase change material suitable for the low temperature field.The heat conduction enhanced shaped phase change material is prepared by the melt blending method.Study the encapsulation performance of the carrier material,the leakage resistance and thermal performance of the composite material via characterization test for the composite material.And study the heat storage/release performance of the composite material by numerical simulation methods.The main innovations and experimental work are as follows:(1)In order to select the modified sepiolite with the best encapsulation performance,the modified sepiolite/stearic acid fixed phase change material was prepared,and the encapsulation performance,thermal stability and thermophysical properties of the three modified sepiolite were evaluated by leakage test and characterization analysis.The results show that the modified sepiolite fiber has the best packing performance and good thermal stability and physical property.(2)Based on the dependence of the packing performance of the modified sepiolite fiber and the heat storage/release performance of the composite material on the thermal conductivity,expanded graphite was used as the high thermal conductivity filling material to prepare the thermal conductivity enhanced shaped composite,and the influence of the mass fraction of expanded graphite on the load performance and thermal conductivity was studied.The experimental data show that the addition of graphite has a linear relation with the thermal conductivity of the composite,which can effectively improve the thermal conductivity of the composite.(3)In order to maximize the encapsulation performance of sepiolite fiber,a series of fixed composites were prepared by modifying sepiolite fiber under different conditions of HCL modification.The results showed that the improvement of modification conditions could increase the loading mass fraction of stearic acid,butthere were some limitations,and the improvement under the optimal modification conditions was less effective than that under the modification conditions.(4)In order to explore the encapsulation efficiency of other load substrates and the thermal properties of composites aim to form a contrast with sepiolite fiber,mica powder of different mesh sizes was used as the carrier material,and expanded graphite was used as the thermal conductivity reinforcement to prepare shaped composites.The adsorption properties of different mica powders were studied.After the mica powder mesh number is optimized,the thermal conductivity enhancement experiment is carried out to study the storage and heat release performance parameters of the composite material and make a comparative analysis.The results show that compared with other mica powders,mica powders of 100-mesh mica powders have the best adsorption performance.However,compared with the modified sepiolite fiber,the loading performance is insufficient,and the addition of expanded graphite is not enough to make up the difference.(5)In order to study the heat storage/release performance of modified sepiolite fire-expanded graphite 15wt%/stearic acid 60wt%,numerical simulation was used as the research method to simulate the heat storage/release efficiency of the composite by changing working conditions through the control variable method,and the influence of different inlet conditions on the heat storage/release efficiency was analyzed.The results show that the material prepared in this paper has good heat storage/release performance,the inlet temperature and inlet velocity have influence on the heat storage/release capacity of the composite material,and the inlet condition with the highest heat storage/release efficiency is determined.