The impact of the backfill direction on the backfill cooling performance using phase change materials in mine cooling

The deep mine radiation cooling system using cold load and storage (CLS) functional cemented paste backfill (CPB) has been proven to be better in maintaining a more comfortable mine environment with lower energy consumption than conventional cooling methods. Three typical backfill methods with CLS-functional CPB, upwards backfill, downwards backfill and wall backfill, which have different positional relationships between the cold radiant surface and the cooled space, resulted in different cooling performances. A numerical model constructed by CFD was verified by experimental results to obtain the heat transfer characteristics of the three backfill methods. The dimensionless temperature, dimensionless direction, and heat transfer coefficient were defined to identify the heat transfer mechanism of the three methods. The experimental and simulation results show that the downwards backfill can accelerate the heat transfer rate, make the stope's temperature more uniform, and better meet the requirements of deep mine mining temperature. The dimensionless temperature variation perpendicular to the direction of cold transfer is expressed by the QP model for upwards and downwards backfill conditions and the ExpDec1 model for wall backfill conditions. Compared with the homologous cold radiation system, the three backfill methods have satisfactory heat transfer cooling performance. The results of this study can provide a reference for the improvement of the cooling effect of CLS-functional CPB and mine cooling system design using CLS-functional CPB.