Mechanical and thermo-physical properties of heat and energy storage backfill based on MicroPCMs

Abstract

Combining backfill mining with geothermal resource exploitation, geothermal extraction is achieved by using heat and energy storage functional backfill to achieve a win-win situation of mineral and geothermal co-mining. In this study, MicroPCMs were partially substituted for tailings to prepare phase change backfill material. The influence of different MicroPCMs contents (0, 5, 10, 15, 20 wt%) on the mechanical and thermophysical properties of backfill was investigated to determine the optimal MicroPCMs contents. The results showed that with the increase of MicroPCMs content, the strength exhibited a cliff-like drop at 5% followed by a gradual decline, as confirmed by the XTDIC full-field strain deformation measurement and analysis system. The thermal conductivity and thermal diffusivity decreased with the increase of MicroPCMs content, while the volumetric specific heat capacity and enthalpy showed an increasing trend. SEM scanning results indicated that MicroPCMs would fracture under mechanical action, and the fracture proportion increased with the increase in MicroPCMs content. The recommended MicroPCMs content was around 15 wt%, where the compressive strength, volumetric specific heat capacity, and enthalpy reached 5.2 MPa, 1.6 MJ/(m3·K) and 6.16 J/g, respectively. This study provides valuable insights into the influence of MicroPCMs on the strength and thermal properties of backfill materials.