Study on the thermal - mechanical properties and heat transfer characteristics of heat storage functional backfill body

Abstract

Heat storage functional backfill can realize the synergistic mining of the associated geothermal resources while ensuring the safe mining of the deep coal resources. Study on the thermal - mechanical properties and heat transfer characteristics of heat storage functional backfill body (HSFBB) is of great significance. In this paper, paraffin (PA) and expanded graphite (EG) were used to prepare composite phase change material (CPCM), and its optimal ratio was determined, firstly. Then, coal gangue, tailings, CPCM and cement were used to prepare the HSFBB, and the influence of CPCM content on the thermal and mechanical properties of HSFBB was determined. Finally, the influence of CPCM on the heat transfer characteristics of HSFBB was analyzed by means of numerical simulation. The results showed that the optimum mass fraction of EG in CPCM was 10%. The heat stored per unit volume of HSFBB was proportional to the CPCM content, while the thermal conductivity was the opposite. With the increase of CPCM content, the strength and stiffness of HSFBB weakened, the pore and overall deformation increased, and the HSFBB shown obvious ductility characteristics. CPCM content and latent heat had a significant influence on the overall temperature rising rate of HSFBB and the temperature rising process of HSFBB at different locations. However, the phase change interval only had a weak influence on the temperature rising process of HSFBB far away from the heat source.