Preparation Of Biocharcoal-based Shape-stable Phase Change Material And Investigation On Its Application Of Thermal Insulation In Container

With the proposal of the major strategy of“21st Century Maritime Silk Road”,China has increased the maritime trade with Asian and African countries and provided a great opportunity for the development of ASEAN countries.At the same time,as an indispensable means of loading for maritime trade,the containers have ushered in a great opportunity for development.According to statistics from the ministry of transportation,Chinese container throughput increased from 190 million TEU to 238 million TEU between 2013 and 2017,with an average annual growth rate of 5.8%.However,along with the transportation of goods on the temperature requirements more and more strict,some products in the transport process need to be insulated,and the traditional containers cannot play an important role in the process of the insulation.Therefore,finding a low cost,low energy consumption and green improvement method to upgrade the traditional container has become an optimal research topic.Phase change materials(PCMs)have the advantages of high latent heat,appropriate melting point,great thermal stability,low cost and non-corrosiveness.Therefore,those could be used as the thermal insulated materials for containers.However,there are two main disadvantages of PCMs that should be overcame.The one is that the thermal conversion would be weakened as a result of the low thermal conductivity of the PCMs.The other one is that the leakage usually occurred during the phase change processes.Those drawbacks would limit the practical application of PCMs.In order to resolve problems mentioned above,the pinecone biochar(PB),made from the pyrolysis of pinecones,and the palmitic acid(PA)were used as the supporting materials and the core materials to prepare shape-stable PCMs(PA/PB)by the vacuum impregnation.The average pore diameter of pinecone biochar prepared in this study was 3.078 nm,the average pore volume and specific surface area were 0.17cc/g and 289.69 m~2/g,respectively,and the thermal conductivity was 0.3417 W/(m?K).The PA/PB in this study was prepared by the method of vacuum impregnation,and there was no obvious leakage appeared when the mass ratio of PA and PB was 6:4.The characteristic of PA/PB was analyzed by the means of scanning electron microscope(SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),fourier infrared(FT-IR),thermal conductivity test,thermal and cycling test.The results showed that PA was uniformly adsorbed on the PB and there was no chemical reaction between the PA and PB,meaning the original characteristics of the two components did not change.The melting point and freezing point of PA/PB were 59.25°C and 59.13°C,respectively,the melting enthalpy and the solidification enthalpy were 84.74 kJ/kg and 83.81 kJ/kg,respectively.The PA/PB had favorable thermal stability,and there was no obvious mass loss when the temperature was lower than 152°C,which could meet the practical requirements of the temperature in the process of container shipment in actual.The thermal conductivity of PA/PB was 0.3926 W/(m?K),which was 43.76%higher than that of PA.After 50 thermal cycles,the melting point and freezing point of PA/PB only changed by0.24%and 0.67%,and the melting enthalpy and solidification enthalpy only decreased by3.55 kJ/kg and 2.97 kJ/kg.Therefore,it could be used as the thermal insulated materials of the container,which can withstand the test of the alternation of day and night temperature during the voyage.What’s more,the ANSYS was used to compare the temperature field of container with adding the shape-stable PCMs and without adding the shape-stable PCMs.It drew a conclusion that the maximum temperature of insulated container was 4.89°C lower than that of traditional container,and the minimum temperature was 1.19°C higher than that of traditional container.In order to solve the problems of low thermal insulation and high refrigeration cost of traditional containers,the pinecone biochar made from pyrolyzing pinecone as the supporting material of palmitic acid in this study,which not only play a role to some extent in the thermal insulation of container,but also increase the innovation in the research of shape-stable phase change materials and provides theoretical and technical support for the application of shape-stable phase change materials in other thermal insulation fields.