Preparation And Study On Sodium Acetate Trihydrate-sodium Sulfate Decahydrate/Expanded Perlite Phase Change Heat Storage Materials

Due to the current global energy shortage,reducing building energy consumption is imperative.The phase transition materials have the ability to store heat energy and are widely used in building materials and temperature control equipment.The development of phase change heat storage materials with high heat transfer performance and stability is helpful to overcome the limitation of solar energy utilization and effectively solve the problem of unbalanced distribution of solar energy.The combination of phase change materials and carrier material can avoid the leakage of phase change materials to a certain extent,which is beneficial to the application of phase change materials in practical engineering.Inorganic hydrate salt phase change materials have higher latent heat,wider temperature range and lower cost,but they usually have larger defects of supercooling degree and phase separation.In this paper,two kinds of inorganic hydrate salts,sodium acetate trihydrate(CH₃COONa·3H₂O)and sodium sulfate decahydrate(Na₂SO₄·10H₂O),which have high latent heat of phase change,were selected as phase change materials to prepare eutectic salt.In this process,the effects of additives on the undercooling degree and phase separation of eutectic salt were studied.Sodium acetate trihydrate-sodium sulfate decahydrate(CH₃COONa·3H₂O-Na₂SO₄·10H₂O)/expanded perlite(EP)composite phase change energy heat materials was prepared by direct adsorption method,which can be used in building energy conservation,and its thermal properties were characterized and analyzed.Specific research contents are as follows:1.Sodium acetate trihydrate(CH₃COONa·3H₂O)and sodium sulfate decahydrate(Na₂SO₄·10H₂O)were mixed at a mass ratio of 1:1,eutectic salt was prepared by melt-cooling method,and borax with different contents was added as nucleating agent.The results show that,compared with the pure components of sodium acetate trihydrate(CH₃COONa·3H₂O)and sodium sulfate decahydrate(Na₂SO₄·10H₂O),the undercooling degree of eutectic salt is obviously reduced.With the increase of borax content,the undercooling degree of eutectic salt firstly decreased and then increased.When the addition amount of borax was 3 wt%,the undercooling degree of eutectic salt decreased to 1.4?at the lowest.For the defect of phase separation,sodium carboxymethyl cellulose(CMC)was added into the eutectic salt.The phase separation phenomenon is completely eliminated when the content of sodium carboxy methyl cellulose is 1.5 wt%,and the degree of undercooling of eutectic salt in the system is further reduced to 0.8?.2.Expanded perlite(EP)was selected as support material.The eutectic salt was combined with expanded perlite(EP)by direct adsorption method to prepare the phase change heat storage material of sodium acetate trihydrate-sodium sulfate decahydrate(CH₃COONa·3H₂O-Na₂SO₄·10H₂O)/expanded perlite(EP)composite.The optimum adsorption particle size of expanded perlite(EP)and the maximum adsorption amount of eutectic salt were determined by seepage experiments.The results show that the system with the least leakage degree of the composite phase change material,the particle size of expanded perlite(EP)is 1.5?2.0 mm,and the adsorption capacity of eutectic salt is 65 wt%.3.The morphology and thermal characteristics of sodium acetate trihydrate-sodium sulfate decahydrate(CH₃COONa·3H₂O-Na₂SO₄·10H₂O)/expanded perlite(EP)composite phase change heat storage materials were characterized and tested by scanning electron microscopy(SEM),differential scanning calorimetry(DSC),thermal conductivity test,stability analysis and thermal storage/release performance analysis.The results show that the eutectic salt of sodium acetate trihydrate(CH₃COONa·3H₂O)and sodium sulfate decahydrate(Na₂SO₄·10H₂O)are uniformly adsorbed in the inner surface and the pores of the expanded perlite(EP).The melting enthalpy of the composite phase change material is 141.5 k J/kg,and the solidification enthalpy is128.7 k J/kg.The thermal conductivity of the composite phase change material is0.0483 W/(m·K),which is between the thermal conductivity of expanded perlite(EP)and eutectic salt,indicating that the composite phase change material can not only effectively heat transfer,but also achieve the effect of heat preservation in the process of storage/release heat.After 60 cycles of hot and cold,the mass loss rate of the composite phase change material is only 1.6%,which indicates that it has good thermal stability and can be used repeatedly to adjust the room temperature and play the role of heat storage/release.The above studies indicate that the phase change heat storage material,sodium acetate trihydrate-sodium sulfate decahydrate(CH₃COONa·3H₂O-Na₂SO₄·10H₂O)/expanded perlite(EP)composite prepared by direct adsorption method in this paper,can effectively store and release heat in the process of heating and cooling.It has a good temperature control effect and can be applied to the field of building energy conservation.