Study On The Preparation And Heat Storage Performance Of Fatty Acid-based Composite Phase Change Materials

As a common organic phase change material,fatty acid has the general formula of C_n H_2nn O₂,which has the characteristics of cyclic melting/crystallization stability,non-toxicity and non-corrosiveness etc.It has been attracted comparatively wider attention in the fields of building energy-saving and temperature regulation textiles etc.There are mainly stearic acid?SA?,palmitic acid?PA?,myristic acid?MA?,lauric acid?LA?,citric acid?CA?and octanoic acid?OA?.However,single fatty acid has a fixed phase transition temperature and relatively higher melting temperature and cannot be directly applied to the fields such as architecture,air conditioning and cold storage etc,its relatively lower thermal conductivity also limits the industrial applications.Therefore,the researches on fatty acid based composite phase change materials are of comparatively important significance and applicable value.In allusion to the shortage that single fatty acid has a fixed phase transition temperature and relatively higher melting temperature and cannot be directly applied to the fields such as architecture,air conditioning and cold storage etc,decanoic acid and tetradecyl alcohol were selected as phase change materials in this investigation,decanoic acid-tetradecyl alcohol composite phase change material was prepared and the experimental investigations of its heat storage performance were made.Decanoic acid-tetradecyl alcohol composite phase change material was selected as the matrix,decanoic acid-tetradecyl alcohol/nanoparticle composite phase change materials were prepared by the addition of three types of nanoparticles with higher thermal conductivity,and the experimental investigations of their heat storage performance were made.Their phase transformation processes with nanoparticles and without nanoparticles was simulated by the ANSYS software.The main contents of the whole research are as follows:1.Experimental investigations on the preparation and heat storage performance of decanoic acid-tetradecyl alcohol composite phase change material Decanoic acid-tradecyl alcohol composite phase change material was prepared by the melt-blending method with different molar ratios of decanoic acid and tetradecyl alcohol,and its main thermophysical properties were measured by KEITHLEY 2700Data Acquisition System,NETZSCH STA449F3 Synchronous Thermal Analyzer and Hot Disk TPS2500 Thermal Conductivity Tester.The experimental measurement results showed that,as the molar ratio of decanoic acid to tradecyl alcohol was 7:3,the phase transition temperature of the prepared decanoic acid-tetradecyl alcohol composite phase change material was 20.34°C,and its latent heat was 163.85kJ?kg^-1;the thermal conductivity was more intense near the phase transition temperature,as it was raised to a certain temperature,the thermal conductivity was gradually stable and slightly lower than the thermal conductivity of the solid state;decanoic acid-tetradecyl alcohol composite phase change material with the molar ratio of 7:3 was measured for600 times of the melting-solidification cycles,the measurement results verified that the composite phase change material had favorable thermal stability.2.Experimental investigations on the preparation and heat storage performance of decanoic acid-tetradecyl alcohol/nanoparticle composite phase change material s Decanoic acid-tetradecyl alcohol composite phase change material with the molar ratio of decanoic acid and tetradecyl alcohol of 7:3 was selected as the matrix,decanoic acid-tetradecyl alcohol/nano-graphite composite phase change material,decanoic acid-tetradecyl alcohol/nano-copper composite phase change material and decanoic acid-tetradecyl alcohol/nano-aluminum composite phase change material were prepared by adding different mass fractions of nano-graphite,nano-copper and nano-aluminum.The experimental results showed that,the thermal conductivity of the decanoic acid-tetradecyl alcohol/nanoparticle composite phase change materials had a relatively larger increase relative to the matrix,and had no significant effect on the ir latent heats and phase transition temperatures;as the mass fraction of the added nano-graphite was 0.6%,the main thermophysical properties of the prepared decanoic acid-tetradecyl alcohol/nano-graphite composite phase change material were the best compared with the addition of the other mass fractions of nano-graphite,its thermal conductivities of the solid and liquid phases were respectively increased by 39.5%and35.2%,its phase transition temperature and latent heat were respectively 20.42°C and154.25 kJ?kg^-1,and it had favorable thermal stability;as the mass fraction of the added nano-copper was 0.4%,the main thermophysical properties of the prepared decanoic acid-tetradecyl alcohol/nano-copper composite phase change material were the best compared with the addition of the other mass fractions of nano-copper,the thermal conductivities of the solid and liquid phases were respectively increased by 6.64%and11.04%,its phase transition temperature and latent heat were respectively 20.26°C and 157.85 kJ?kg^-1,and it had favorable thermal stability;as the mass fraction of the added nano-aluminum was 0.5%,the main thermophysical properties of the prepared decanoic acid-tetradecyl alcohol/nano-aluminum composite phase change material were the best compared with the addition of the other mass fractions of nano-aluminum,the thermal conductivities of the solid and liquid phases were respectively increased by 15.77%and 29.39%,its phase transition temperature and latent heat were respectively 20.23°C and 155.12 kJ?kg^-1,and it had favorable thermal stability.3.Simulation analysis of phase change process of composite phase change materials Phase transition processes of decanoic acid-tetradecyl alcohol composite phase change material and decanoic acid-tetradecyl alcohol/nanoparticle composite phase change material were simulated by the ANSYS software.The simulation analysis results were consistent with the experimental results,or the addition of three types of nanoparticles could effectively improve thermal conductivity of decanoic acid-tetradecyl alcohol composite phase change material and the thermal conductivity of the composite phase change material with nano-graphite was the best.The research work and the research achievements obtained in this thesis are expected to solve the problem that single fatty acid has a fixed phase transition temperature and relatively higher melting temperature and cannot be directly applied to the fields such as architecture,air conditioning and cold storage,etc.By exploring preparation and heat storage performance of fatty acid based composite phase change materials suitable for building energy-saving applications,which will provide a reliable experimental evidence and technical foundations for their applications in calefaction or heating of industrial and civil building structures.