The Preparation And Thermal Properties Of Fatty Acids Ternary Eutectic Mixture Composite Phase Change Material

Fatty acid phase change materials with high melting latent heat, low degree of supercooling, nontoxic, nonflammable, good stability and building material with good biocompatibility and other advantages, its application in the field of building energy conservation, which can effectively reduce indoor temperature fluctuation, improve the indoor environment of comfort, and thus become one of the hot research field of energy saving building.Fatty acid of phase change materials research is mainly concentrated in single and binary eutectic fatty acids, little in the ternary eutectic fatty acid phase change materials. Based on the single fatty acid as raw material, prepared three kinds of ternary eutectic fatty acids, solid-liquid reaction kinetics was studied, and to study its thermal properties; With the preparation of ternary eutectic fatty acid as phase change material, organic modified montmorillonite, expanded graphite were selected for the porous (layer) based materials, composite phase change material for preparation of free package, and the prediction and Study on thermal performance and energy saving effect of the composite phase change materials by numerical simulation and experiment method. The research contents and results are as follows:(1) Select five kinds of fatty acid as raw material, according to ternary mixing to obtain ten kinds of fatty acid eutectics. DSC analysis the phase change temperature and phase change latent heat of ternary fatty acid eutectic, selected three kinds of phase change materials in energy saving buildings for the use of ternary eutectic of fatty acid and the quality ratio: CA(decanoic acid)-MA(myristic acid)-PA(palmitic acid)=7:2:1, CA-MA-SA(stearic acid)= 7:2:1 and CA-PA-SA=8:1:1; according to the second law of thermodynamics and the of theory lowest eutectic, calculate the ternary eutectic fatty acid quality ratio of CA-MA-PA=0.731:0.194:0.075, CA-MA-SA=0.709:0.188:0.103 and CA-PA-SA=0.770: 0.115:0.115. Compared experimental values and the calculated values are very close, the theoretical calculation method, can be used for ternary eutectic fatty acid PCM combination and proportion of choice. Ternary eutectic the phase transition temperature are lower than the single fatty acids, eutectic method is used to obtain different phase change temperature, the expansion range of phase change temperature of fatty acid phase changematerials.The performance and properties were studied of ternary eutectic fatty acid. FT-IR spectra show that the molecules of fatty acids between the hydrogen bonding is only two association, no chemical reaction. Thermogravimetric analysis found that the ternary eutectic material under 100℃ has good thermal stability.500 times thermal cycling test showed that the phase change temperature and phase change latent heat of CA-MA-PA,CA-MA-SA,CA-PA-SA is change -0.88%,0.06%;-0.78%,1.77%;-0.08%,1.57%, ternary eutectic material with good thermal cycling stability. Storage/release test and the temperature damping rate indicates that ternary eutectic mixture has good temperature regulation function, to meet the energy requirements of phase change property of building material.According to calculating dynamic method of Kissinger ternary eutectic fatty acid activation energy in 250～350 kJ·mol-1, correlation coefficient square R2>0.97, shows that ln(β/Tp2) and (l/Tp) a significant linear relationship. Ternary eutectic solid-liquid phase change reaction of fatty acid reaction order was about 1, shows that the ternary eutectic fatty acid solid-liquid phase reaction is first order reaction.(2) Ternary eutectic fatty acid as phase change material, organic modified montmorillonite (OMMT) for supporting materials, the preparation of ternary eutectic fatty acid/OMMT composite phase change materials(CPCM) and the best quality proportion of three kinds of CPCM was determined, CA-MA-PA:OMMT=7:3, phase change temperature and latent heat were 21.06℃ and 103.40 J·g-1; CA-MA-SA:OMMT=7:3, the phase change temperature and latent heat were 20.14℃ and 89.14 J·g-1; CA-PA-SA:OMMT=6:4, phase change temperature and latent heat were 24.56℃ and 91.81 J·g-1.FT-IR and X-RD test results show that the ternary eutectic fatty acids and OMMT simply chimeric relations; Contrast OMMT, SEM observation to the CPCM is thick layer, edge layer passivation, and have obvious adhesion phenomenon of reunion between lamella, showed that the ternary eutectic CPCM fatty acids and OMMT have better compatibility; TG experiments showed that CA-MA-SA/OMMT quality loss mainly comes from the thermal decomposition weightlessness of CA-MA-SA, the protective effect of OMMT on CA-MA-SA, main weightlessness temperature range move to high temperature of 11℃, under 120℃ has good thermal stability; CA-PA-SA/OMMT phase change temperature and latent heat after 500 times of hot and cold cycle changes within 0.05%, indicating the good long-term stability; Thethermal conductivity of the CA-MA-SA/OMMT was 0.352 W·m-1·K-1, lower than thermal conductivity of CA-MA-SA. Storage/release test and the temperature damping rate showed that three kinds of ternary eutectic fatty acid/OMMT CPCM has better effect of temperature regulation function.Solid-liquid reaction kinetics of CA-MA-SA/OMMT, Ea=14.22 kJ·mol-1, verify the CA-MA-SA and OMMT is a chimeric relationship, room temperature can be achieved; according to the shape index obtain reaction order in 1.16～1.20, solid-liquid reaction order of CA-MA-SA/OMMT is 1.2.(3) Ternary eutectic fatty acid as PCM and expanded graphite (EG) as a supporting material, to prepare ternary eutectic fatty acid/EG composite phase change materials by vacuum adsorption, three kinds of ternary eutectic fatty acid with best quality ratio of EG are 13:1, latent heat of 121.75～143.64 J·g-1, and the theoretical calculation of latent heat value is very close.FT-IR and X-RD results show that the PCM and EG without chemical reaction, is a physical blending system; SEM observations of graphite expansion generated after rich mesh microporous worm-like EG, ternary eutectic fatty acids distributed evenly in the porous structure of EG, the compatibility is good; TG experiments showed that CA-PA-SA/EG quality loss mainly comes from the thermal decomposition weightlessness CA-PA-SA, the protective effect of EG on CA-PA-SA, main weightlessness temperature range move to high temperature 20℃, under 130℃ has good thermal stability; After 500 times of psychro-thermal cycles, the thermal physical properties of CPCM has no obvious attenuation, phase transition temperature variation ±1℃, latent heat change ±2%, prove its long-term stability and reliable; Thermal conductivity of CA-MA-PA/EG, CA-MA-SA/EG and CA-PA-SA/EG is 1.64 W·m-1·K-1,1.38 W·m-1·-1 and 1.87 W·m-1·-1, the coefficient of thermal conductivity of ternary eutectic fatty acids increase by about 298%. Storage/release test and the temperature damping rate showed that three kinds of ternary eutectic fatty acid/EG CPCM has better effect of temperature regulation function.Ternary eutectic fatty acid/EG composite phase change materials of solid-liquid reaction kinetics, Ea=9.038 kJ·mol-1, verify between the ternary eutectic fatty acids and EG is physical adsorption, not chemical adsorption (Ea>85 kJ·mol-1), can be obtained quickly at room temperature; according to the shape index obtain reaction order about 1, solid-liquid reactionorder of CA-MA-SA/EG is carried out according to the first-order reaction.(4) With high thermal conductivity CA-PA-SA/EG and building gypsum powder as raw material, adopts the direct join prepared phase change plasterboard, add 4% of the glass fiber reinforced the strength of phase change plasterboard. DSC test results show that the dosage of 10% phase change plasterboard the phase transition temperature 22.53℃, latent heat 14.20 J·g-1, and with the increase of dosage, phase change temperature and latent heat increases, when the dosage of more than 30%, gypsum board is easy to fracture. Experiments show that the compressive strength with the increase of dosage of CPCM, the compressive strength decreased. Combined with latent heat and the compressive strength, the selection of CPCM dosage was 20%.Based on ANSYS to establish mathematical model, simulation analysis of the phase transition process of phase change plasterboard, and experiment validation, simulation results show that the simulated results and experimental results are basically identical, prediction can be realized by using numerical simulation experiment. When the heat source or cold source on both side of phase change plasterboard, raise the temperature of phase transformation plasterboard to phase transition temperature, phase change in room temperature fluctuation is small, and continue for a period of time under a certain temperature. When the heat source or cold source at the top of the phase change plasterboard, due to the phase change room and ordinary room temperature rapidly heated, phase change plasterboard has no marked impact on the surrounding temperature, but there was significant difference between the phase change plasterboard and plasterboard.The effects of different dosage (10%,20%,30%) storage/release properties of phase change plasterboard, with the increase of dosage of CPCM, phase change plasterboard the greater impact on the environment temperature, the temperature control ability, the more the longer, the temperature damping coefficient was 17.26%～17.26%, with the increase of CA-PA-SA/EG content, temperature and damping ratio increases gradually, the higher dosage, phase change plasterboard model of temperature change is slower, the stronger the ability. 100 the thermal cycling test show that phase change plasterboard with good cycling stability.