相变储能充填体孔隙结构及强度劣化机制研究

Pore structure and strength deterioration mechanism of phase change energy storage backfill

为探究相变储能充填体孔隙结构特征及其对充填体强度劣化的影响,以硬脂酸丁酯为相变材料,膨胀珍珠岩为吸附介质制备复合相变材料,将其与水泥、尾砂混合制备不同复合相变材料添加量的相变储能充填体,并采用CT(电子计算机断层)扫描、MRI(核磁共振成像)分析、单轴压缩试验等方法得到不同添加量相变储能充填体的强度特征和结构特征,分析其影响机制。研究结果表明:(1)相变储能充填体孔隙率随添加量增大逐渐增大,其中大孔孔隙率近似线性增加,大孔占比逐渐增加,孔隙趋近球体。(2)随着相变材料添加量增加,充填体连通性增大,孔喉长度增加,大孔径孔隙数量增多,孔喉配位数集中在5以下,分形维数先下降再大幅上升,孔隙分布复杂。(3)当复合相变材料的添加量为5%时,受大孔隙及孔隙连通性增大的影响,充填体单轴抗压强度下降了30.2%;当复合相变材料的添加量为10%时,孔径分布趋于均匀,充填体单轴抗压强度下降了48.9%。

In order to explore the pore structure characteristics of phase change energy storage backfill and their influence on the strength deterioration of backfill,a composite phase change material was prepared with butyl stearate as the phase change material and expanded perlite as the adsorption medium.Cement and tailings were mixed to prepare backfills with different additive amounts of the composite phase change material.The strength and structure characteristics of the phase change energy storage backfill with different addition amounts were obtained by using the methods of CT(computer tomography)scanning,MRI(magnetic resonance imaging)analysis,and uniaxial compression test,and the influence mechanism was analyzed.The results show that:i)The porosity of phase change energy storage backfill increases gradually with the increase of the addition amount.The macropore porosity increases approximately linearly,the proportion of macorepores increases gradually,and the pores approximate to sphere.ii)With the increase of the amount of phase change material,the connectivity of the backfill increases,the pore throat length increases,and the number of macropores increases.The pore throat coordination number is concentrated below 5,and the fractal dimension decreases first and then increases significantly,resulting in complex pore distribution.iii)With 5%additive amount,the uniaxial compressive strength of backfill decreases by 30.2%due to the increase of macropores and pore connectivity.With 10%additive amount,the pore size distribution becomes uniform and the uniaxial compressive strength decreases by 48.9%.