Simulation of Non-Stationary Heat and Mass Transfer in Longwall Mining, Considering Heating and Cooling Features of Mining Equipment

Adverse microclimatic conditions in mines and shafts negatively affect both health of employees and the safety of workflows as a whole. The existing models to calculate microclimatic parameters can consider technogenic heat emission sources (mining machinery and equipment) only in «operation» and «shutdown» modes. For the first mode, heat emissions are adopted as constant; for the second mode, they are identically zero. In reality, however, thermal inertia is specific to the equipment. It is crucial to consider it for the correct simulation of aerological processes in mine ventilation networks. A dynamic model enabling the calculation of changes in microclimatic parameters (temperature and relative air humidity) for the preset time interval and equipment operation mode in the space of longwall mining and the adjacent fitting forklifts has been suggested in the article to increase the safety of mining operations. The key feature of the model is the registration of non-stationary heat transfer between the air and the power train (the source of heat emissions). The airflow of the motor by ventilation is provided in order to protect the source motor against overheating. Upon the shutdown of the source, the cooling system is switched off, and the source is cooled due to the natural heat exchange with the air. The simulation results are provided as a space-and-time air temperature field. The high-precision simulation is confirmed by insignificant differences between calculated and experimental values. Based on the developed model, an approach to forecasting heat load levels for an employee during a work shift is proposed. The approach is based on the simulation data and the data on the employee’s location during the work shift (planogram-based). The results of the simulation show insignificant differences compared with the data of continuous measurements, which can be explained by the deviation of a real operational process from a modeled planogram. Based on the above-mentioned, it can be concluded that the model is applicable for the assessment of the thermal stress level to which employees are exposed when attending operating working areas.