Studies Of Micro-climate In Deep Coal Mining Face

With the increasing need of energy source, the depth of coal mining increased, which leads to the rising of temperatures of the original rock. Also the problem of high-temperature thermal injury of mining and tunneling face become more and more serious. The reasons of thermal damage problems are multifaceted, except heat emission of compressed air and mechanical equipment, the effect of the deep elimination of heat from adjacent rock and the effect of oxidation in goaf are also very significant. Therefore, it is necessary to study the ventilation and thermal environmental conditions of roadway and mining face underground, and seeking the effective ways to improve the micro-climate underground. At present, the most widely used judging criterions are single objective parameters such as dry-bulb temperature in coal industry domestic and abroad, and the upper limits of them are also varied. They are commonly based on the long-term practical experience, but lack of adequate theoretical basis. With the increase of mining depth and its environment changes, it is necessary to do some amendments to the indicators or to propose some new indicators.In this paper, combining with the actual situation of China's underground mining face, through analyzing and suming up the current domestic and international human comfort model for extreme thermal environments, it is considered that: the "Coal Mine Safety Regulations" of China using dry-bulb temperature and wind velocity as the evaluations of underground thermal damage indicators, but in the actual operation process, the thermal comfort level of miners is a comprehensive result of physiological and psychological, objective and subjective. It is difficult to achieve a comprehensive evaluation of the purpose of underground thermal damage by using simple dry-bulb temperature or air velocity. So it is suggested that using the mean skin temperature which under the condition of the heat balance as extreme thermal environments human comfort evaluation criteria.For underground micro-climate, there's a significant influence of air temperature field and flow field for the safety of coal mines' production and miners' health. Therefore, this paper considered a typical U-shaped stope of geometry, geological conditions and ventilation. Through the laboratory scale model tests, the correctness of the fluid / porous medium dynamic model which had been presented in related literature was verified. According to the simulation results of temperature, wind velocity and experimental conditions of three miners in Dongtan coal mine, the level of thermal comfort of the three miners was evaluated and analyzed.According to the mean skin temperatures when the miners are working underground with different metabolic conditions reach thermal equilibrium, it is found that it is possible to extend 26°C which is the upper limit of dry-bulb temperature of "Coal Mine Safety Regulations" of China to 28°C. And by the same environmental conditions, the new criterion is validated by skin wettness, sweating rate, upper limit of working time when the miners are doing jobs of different intensity.Finally, in order to evaluate the underground thermal environment comprehensively, this paper has applied the heat balance model of the human body by reference to ASHRAE's new effective temperature diagram of human comfort zone criteria, selecting the mean skin temperature, metabolic capacity, clothing thermal resistance, dry-bulb temperature, radiation temperature, wind speed, relative humidity and other objective and subjective evaluation indicators to synthesize and draw out the thermal comfort zones which are suitable for different intensity of works as the evaluation criterias for extreme thermal environment. When the conditions of heat balance and sweating rate are satisfied, according to the miner's mean skin temperature when they are doing certain intensity jobs, the thermal comfort zones will be divided into non-working area, comfortable work areas and prohibited areas. According to the metabolic capacity of miners and underground environment parameters, it is possible to draw the corresponding thermal comfort zone diagram.