Researchers from the Department of Earth Resources Engineering at the Kunming University of Science and Technology have developed an innovative cooling system for deep coal mines, where high thermal loads pose a threat to workers’ health and reduce labor productivity. As the depth of mining increases, so do temperatures in mine workings, proving the conventional cooling methods ineffective: the cooled air is quickly carried away by the main ventilation air flow before it can cool down the work areas.
The solution proposed by the Chinese scientists entails the creation of a so-called microclimate zone, an area with a stable closed flow of cold air concentrated right at the work site. The technology is based on a modular convection-radiation system, including copper pipes with a coolant, cooling panels, two fans and guide flaps. This design generates a controlled air flow that keeps the cooled air in the required area, preventing it from leaking into the main ventilation duct. The system operates on the local circulation principle: warm air from the mine shaft is drawn in by fans, cooled on the surface of the panel and directed back to the work area. Thanks to closed circulation, the temperature decreases exactly where needed, without unnecessary energy consumption.
Numerical modeling conducted by the researchers with ANSYS Fluent made it possible to define the optimal operating parameters of the system: a coolant velocity of 0.2 m/s, an incoming air velocity of 0.45 m/s and an outlet height of 70 mm. These values made sure cooling was efficient with minimal power consumption.
Field tests at a depth of more than 1,400 m showed that the new technology increases the cooling capacity by almost 20%, with cooling losses of only 3% at a distance of 7 m compared to 19% for the conventional design. Moreover, when modules are placed on both sides of the mine working, cooling covers the entire work area, i.e., safe temperature and humidity parameters consistent with the international heat comfort index WBGT are observed on 100% of the area.
The system complies with industrial safety requirements and does not disrupt the operation of mine ventilation, occupying no more than 20% of the mine working cross-section. If the permissible concentrations of dust or gas are exceeded, it automatically switches off and activates the enhanced exhaust mode. The entire system responds within 5 seconds thanks to sensors and a programmable controller.
