Abstract
The underground ventilation in coal mine comes from the ground air so that the seasonal fluctuation of atmospheric temperature inevitably has influence upon its climate. The paper obtains a simplified mathematical calculation method of the radial and axial temperature fields to furnish a supplement to air temperature prediction of coal roadway with the emphasis on the influence of seasonal characteristic of inlet airflow. The results reveal that the propagation of radial and axial temperature wave has the similar characteristic of amplitude decay and phase delay. In the radial direction, the main factor is the dimensionless annual cycle time; and in the axial direction, it is influenced by the location-related dimensionless time, the Nusselt number, the Biot number, and the dimensionless annual cycle time. In addition, for the wave amplitude, they present the negative exponential trend as the location increases, the overall shape of which resembles a folded page; for the delayed phase, they present the linear variation trend as the location increases, the overall shape of which resembles a parallelogram. In the paper, the evolution mechanism of temperature field of coal roadway under seasonal fluctuation boundary is profoundly comprehended, which has important guiding significance for the field engineer.
Highlights
Coal is the biggest energy sources in China
The reason is that the heat transport mode between the wall of surrounding rock and air is through convection, which has greatly related to the speed of air current from (20); that is, the parameter A has a close relationship with FoT, Biot Number (Bi); but in the interior, it is through the conduction, which has only relationship with the thermal diffusivity of surrounding rock, as well the parameter C is only a function of FoT
The evolution mechanism of temperature field of coal roadway under seasonal fluctuation boundary is elaborated in detail, involving the radial and axial direction, to better implement the air temperature prediction in the underground high-temperature mine
Summary
Coal is the biggest energy sources in China. By statistics, it accounted for about 60.4 percent in the primary energy consumption in 2017 [1]. The variation rules of airflow temperature in underground mine are very complex because of the influence of many factors, principally including the heat dissipation from surrounding rock and the inlet initial temperature from atmosphere [6]. Through comparing with the analytic solution of a halfinfinite plane on even ground, we previously [37] analyzed the mathematical solution of radial temperature field of surrounding rock in detail, and further take a supplement to it, the correctness of which is verified by the experiment in the paper On this basis, the mathematical solution of axial temperature distribution can be obtained from the law of conservation of energy. All the factors that affect the wave amplitude and phase angle of inlet airflow temperature are synthetically evaluated from the whole spacetime perspective when to implement the suitable cooling measures
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