-The Canadian climate features long, cold winters and short, mild summers that provides the opportunity for Vale's Creighton Mine in Sudbury, ON, Canada to manage mine cooling requirements over a 50 year period. The intake air for Creighton Mine's ventilation system is conditioned by continuously pulling ambient air through the Natural Heat Exchange Area (NHEA). The NHEA is a large-scale volume created by previous open-pit and block cave mining at Creighton that contains significant broken rock tonnage with the ability to store ambient coolth and heat on a seasonal basis. The study reported in this paper is part of an on-going collaborative research project conducted by Vale and MIRARCO. The project is investigating options to extend the efficiency of the NHEA system and provide cooler air to deeper levels of Creighton Mine. A threedimensional computational fluid dynamics (CFD) model is being developed and calibrated for dynamic modeling and simulation of the NHEA's thermal physics. The calibrated model will be used to support the assessment of both operation and system design variations to improve the NHEA's performance.

The Natural Heat Exchange Area (NHEA) is a large-scale fractured rock mass at Creighton Mine, created by previous sublevel cave mining, that is used to seasonally store thermal energy with the purpose of moderating the temperature of ventilating air for the underground mine. The use of the NHEA has avoided the mechanical cooling and heating otherwise required due to the seasonal variations in ambient temperatures. The NHEA has 96 doors through which air enters the mine airways through the mass of broken rock; these doors are manually operated to improve the tempering capacity. The empirical strategy for operating the doors has proven successful so far, but additional cooling is needed as mining progresses deeper. This paper describes two models, a three-dimensional computational fluid dynamics (CFD) model and an analytical network model. The models are calibrated to agree with the history of measured temperature, airflow and pressure at the NHEA. The calibrated models will be used together to support the assessment of both operation and systems design variations.

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