Research On Heat Transfer Of Rock Wall In Mine Tunnels

With the extraction of coal at greater depth, and employing higher-powered machinery to improve production levels imposes an increased burden on cooling. Hence, in order to maintain an acceptable mine climate mechanical mine cooling systems are often adopted when ventilation cannot meet the need of cooling. The cooling load is an important parameter which directly effects the choosing of cooling equipment and air cooling units, as well as the cooling performance. Thus, how to calculate the cooling load in deep mines precisely is a critical problem. The heat emission from tunnels takes a biggest part of the total cooling load, but the calculation of this heat transfer process is very complicated. After the terminology of unsteady heat transfer coefficient was first nominated in 1953, lots of scholars around the world have put forward the equations to calculate it, among which Shelbani, Pingsongliangxiong and Foss are three most notable equations. However, some weaknesses exist in these equations: fist, the parameters needed in these equations are too many to make the equations feasible; second, the effect of mass transfer is ignored which makes the calculation result not so precise.In this paper the theory analysis, simulation experiment and on site measure were combined. First, the one dimension unsteady heat transfer model was built under the principle of heat transfer. Then, the two factors– velocity and heat exchange period - which affect the heat transfer of mine tunnels the most was found out, and helped to make guidance for the design of the experiment. Then the experimental system was built under the principle of similarity. Concrete was used to replace the actual sandstone in mine tunnels. The actually heat and mass transfer process was simulated by the experimental system. The unsteady heat transfer coefficient was measured and calculated under different velocity and heat exchange period. Then, the relationship among them was concluded.Additionally, the original temperature of the tunnel is another important parameter in the calculation of heat emission of tunnel. In this paper, an on site survey was carried out. The subjects were four tunnels in a mine located in Shandong Province at different heights from -540m to -790m; the hole was 10m length, and the thermometers which can automatically record the data were used. After the on site measure, an equation indicates the relationship of the original temperatures and the depth of tunnels was concluded.