Beyond dilution: A CFD–based evaluation and optimization of ventilation systems for dual methane–heat hazard control in deep mine galleries

Effective mine ventilation systems must concurrently mitigate methane accumulation and alleviate heat stress, particularly as coal extraction progresses to greater depths. This study used computational fluid dynamics (CFD) to compare blowing, exhaust and mixed ventilation strategies within a typical mine gallery, considering airflow patterns, temperature distribution and methane dispersion. Ventilation effectiveness was assessed using multiple metrics, including dead zone area, methane concentration and ambient temperature. Amongst the systems studied, mixed ventilation was shown to produce the most favourable balance between safety ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mo>≤</mml:mo> <mml:mn>5</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:math> methane) and thermal comfort (&lt;30°C). However, its effectiveness was compromised by supply-to-exhaust short-circuiting. Under mixed ventilation, the airflow pattern within the gallery was divided into three distinct regions governed by different mechanisms: the supply jet, secondary flow and backflow. Parametric analysis revealed that increasing duct spacing significantly mitigates short-circuiting, while setback distance could exert competing influences on methane control and cooling efficiency. A critical ventilation velocity of 12 m/s was identified, beyond which additional airflow would yield negligible environmental improvements while increasing energy demand. This study provides valuable insights into mine ventilation and its intricate effects on the underground environment, contributing to enhanced occupational safety in the mining industry.