Study on a cascade cooling method for fully mechanized top-coal caving faces in high-temperature mines

With increasing mining depth, elevated virgin rock temperatures intensify heat exchange between airflow and surrounding rock, resulting in severe thermal conditions in fully mechanized top-coal caving working faces. Accurate cooling-load assessment and efficient cooling strategies are therefore essential for mine heat-hazard control. In this study, field measurements were conducted to characterize the spatial variations in airflow temperature, humidity, and enthalpy along the working face. A zonal cooling-load calculation method was developed based on the spatially heterogeneous thermal environment, enabling cooling demands to be quantified for different regions. An integrated mobile cooling device combining an air cooler and fan was developed to accommodate the constrained space and continuous advancement of hydraulic supports. Furthermore, a demand-oriented cascade cooling strategy consisting of full-airflow pre-cooling in the intake airway, stepwise cooling along the working face, and localized cooling in the return airway was established by matching cooling capacity with the spatial distribution of thermal loads. The required cooling capacities of the intake airway and working face were 2222.19 and 1682.34 kW, respectively. Six 450 kW air coolers reduced the airflow temperature at the working-face inlet to 21.8 °C, while the integrated mobile cooling device achieved a local temperature reduction of 2.6–3.0 °C and reduced moisture content by approximately 20%. The cascade cooling system reduced the return-air temperature by approximately 5 °C and the overall airflow enthalpy by 28%. The proposed approach provides an integrated framework for spatially matched cooling-load assessment and cooling-system optimization in deep underground fully mechanized top-coal caving working faces.