相变钢球混凝土能源桩热力学特性试验和模拟

Experiment and Simulation on Thermodynamic Characteristics of Phase Change Steel Ball Concrete Energy Pile

为了解决能源桩热交换过程中的土壤热堆积问题,结合相变混凝土与传统能源桩的优点,将相变材料掺入混凝土中形成相变能源桩,以提高能源桩的热交换效率和储热能力.为此,开展了饱和砂土中相变钢球能源桩热力学特性模型试验和模拟,对循环温度作用下桩与桩周土的温度、桩体轴向应变、桩顶位移等进行研究.结果表明:与普通桩相比,加热升温后,相变桩桩体应变比普通桩低;温度稳定时变相桩应变与普通桩相近;相变桩的温度滞后效应和热稳定性更强,换热效率提高,有助于缓解土壤热堆积问题;桩体长期循环温度过高(日间50℃,夜间40℃),桩身温度将超过相变材料的相变温度,储能效果变差,在实际使用时需要采用间歇性作业环境才能达到最佳使用效果.

To solve the problem of soil heat accumulation in the heat exchange process of energy piles,this research combined the advantages of phase change concrete and traditional energy piles,and the phase change material(steel ball)is mixed into concrete to form a phase change energy pile(PCEP)to improve the heat exchange efficiency and heat storage capacity of the energy pile.Then,the thermodynamic characteristics model test and simulation of PCEP in saturated sand were carried out,and the parameters,including the pile temperature and the temperature of the soil around the pile,axial strain in the pile,and pile top displacement under cyclic temperature load,were measured.The results show that the strain in the PCEP is lower than that of the ordinary pile after heating up,and the strain in the PCEP is close to that of the ordinary pile when the temperature is stable.The temperature lag effect and thermal stability of the PCEP are better,and the heat transfer efficiency is higher than that of ordinary piles,which helps alleviate the problem of soil thermal accumulation.The long-term cycle temperature of the pile is too high(50℃during the day and 40℃at night),and the temperature in the pile exceeds the phase change temperature of the phase change material,so the energy storage effect becomes poor.An intermittent working environment is needed to achieve the best behavior in practice.