| With the increase of the mining depth and mechanization, the mine heat injury is increasingly prominent. Mine high temperature and humidity environment seriously endanger the health and safety of staff and affect work efficiency, so it has been one of the major issues restricting the mine safety mining. Therefore, deeply carrying out deep mine heat injury prevention is of great theoretical and practical significance for the safe and efficient mining deep coal resources. Mine air cooler is the end of mine cooling system in order to reduce the temperature of workplace, and its performance directly affects the cooling effect of the air cooler, so the air cooler has been identified as a key research topic in the study field.Dust easily deposited on the surface of the air cooler and steam condensed to water when it touched the cold surface in the use of the mine air cooler, both of which caused the formation of the fouling, thus affecting the air cooler heat exchanger efficiency and the cooling effect. This paper has studied the influence of air cooler outer surface dirt on its heat exchange efficiency.The paper has analyzed the formation of dirt on the air cooler outer surface and its influence on the heat transfer efficiency of the air cooler. Taking the cooling system in a coal mine as prototype, has studied the influence of fouling thickness and grime thermal conductivity on performance of air cooler, obtained the following conclusions:the total heat transfer coefficient of the air cooler reduced with the increase of fouling thickness; the influence is different when the grime thermal conductivity is different, and the impact of fouling on total heat transfer coefficient is weakened with the increase of fouling thermal conductivity; when the thermal conductivity is1.93W/(m K), the overall heat transfer coefficient of the air cooler is substantially constant, so the influence can be neglected.The paper has established a simplified three-dimensional model of the air cooler by using the Gambit software, studied the influence of fouling thickness and its thermal conductivity on the heat transfer effect of air cooler by using the FLUENT software, and obtained the following conclusions:the average outflow temperature increased with the increase of the fouling thickness, so the heat transfer effect is weakened; the greater the fouling thermal conductivity is, the smaller is the impact of fouling on the heat transfer performance of air cooler, and the impact is very weak when the thermal conductivity is1.93W/(m K), which can be neglected.By comparing the simulation results with the measured data, the correctness of the model is verified. Calculated the average temperature of the air handled by the mine cooler of the actual conditions when the pollution is different, and predicted that during the actual cooling process, the presence of dirt will weaken the heat transfer of the air cooler, so the cooling effect will be weakened and get worse with the increase of the dirt thickness, causing that the mine temperature will not reach the design requirements. Under the same operating conditions, the mine ambient temperature will increase about0.3～0.4℃with each additional0.1mm of the outer surface dirt thickness of the air cooler.The paper has optimized the operating pamameter-airflow velocity and structural pamameter-air cooler transverse tube spacing by using the established model considering the fouling influence, and obtained when the flow rate is lower and the transverse tube spacing is proper (St/do=1.5, St is transverse tube spacing and do is external diameter of pipe), the impact of fouling on the heat transfer performace of mine air cooler is weaker.This paper has summarized the current common fouling prevention and control techniques of the heat exchanger, and on this basis proposed grime prevention and control measures of mine air cooler. |
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