The use of packed sphere modelling for airflow and heat exchange analysis in broken or fragmented rock

Abstract

Airflow and heat exchange characterizations through large bodies of fragmented rock in mines, such as those at Creighton and Kidd Creek Mines, reveal them to be still fundamentally only empirical in nature. Analysis of the accepted methods for the design and understanding of geometric properties such as the heat exchange area or the length or shape of airflow passages known to affect heat transfer in, for example, heat exchanger design do not appear in the ‘design’ equations for those bodies of broken rock. This thesis couples a method of discontinuum porous media modelling (referred to as a packed sphere model, abbreviated PSM) with a computational fluid dynamics (CFD) code to develop a proxy methodology for analysis of porous media that incorporates variables of airflow, heat transfer, and geometry (including porosity and tortuosity). Material property values for equivalent continuum fluid dynamics models are established and are found to follow formulations for airflow branches used in mine ventilation network analysis. Laboratory experiments of airflow and heat transfer with the PSMs were compared to CFD results for the same models on a 1:1 scale, to verify the approach and CFD results. Three separate approaches were investigated for the scaling of the results of the PSMs for use in large scale (~1km3) CFD simulations of industrial situations. The result of the work presented in this thesis is a verified methodology for establishing CFD airflow and heat transfer parameters for large bodies of broken and fragmented rock from knowledge of the particle size distribution parameters or the body porosity. The application of the methodology is illustrated with reference to the so-called Natural Heat Exchange Area at Creighton Mine, Sudbury, Ontario.