| Coal remains a key component of China's basic fossil fuel,which has an important strategic position in economic and social development.With the continuous progress of science and technology and the deepening of coal mining depth,a large number of mines transition from shallow mining to deep mining.At the same time,the problem of mine thermal damage is becoming more and more prominent.Workers working in a high-temperature and high-humidity environment for a long time,the physical function and labor efficiency are decreased.At present,the mine usually uses mechanical refrigeration for active cooling,but the mechanical cooling system has high energy consumption and can not achieve the goal of green and healthy mining.Therefore,a passive cooling method based on the coupling of roadway surrounding rock thermal insulation and phase change energy storage plate is proposed in this paper.Considering the effect of low thermal conductivity of phase change materials on energy storage,the heat transfer enhancement of phase change materials was studied at first,and the heat transfer enhancement effects of different heat transfer enhancement techniques on phase change materials were compared by numerical calculation.then the appropriate heat transfer enhancement method is optimized.Then the effects of size and inclination angle on the performance of the composite phase change energy storage plate are studied,and a three-dimensional mathematical model considering the actual working conditions is established and verified by experiments.Finally,based on the above research results,the improvement of roadway thermal environment under the coupling action of surrounding rock thermal insulation and energy storage plate is studied,and the model of coupled cooling system is established.The temperature control characteristics of the coupled cooling system and the influence of different factors on the coupled cooling system are analyzed.Based on this law,the configuration of the coupled cooling system is optimized according to the actual roadway environment to meet the needs of thermal comfort.The main conclusions are as follows:(1)Compared with pure phase change materials,the filling of nano-copper particles,fins and copper foam saved 14.32%,44.83% and 53.44% of the complete melting time respectively,and the platform period of heating wall temperature was prolonged by 15.2%,100% and 112.12%,respectively.During the study period,the average heating surface temperature decreased by 0.12%,0.73% and 1%,respectively.According to the comprehensive consideration,the copper foam with porosity of0.95 and pore density of 30 PPI is selected as the filling material for heat transfer enhancement.(2)The melting process and temperature control law of energy storage plate under different structure sizes are compared and summarized.the results show that compared with length and thickness,the effect of thickness on the performance of energy storage plate is more significant.For the inclination angle,because the heat transfer process is dominated by heat conduction under the filling of porous foam,there is no difference in the performance of the energy storage plate at different inclination angles.(3)It is found that reducing the phase change temperature and increasing the number of energy storage plates can promote the tunnel thermal environment and the temperature control duration,and there is a strong linear relationship with it.Using phase change materials with high latent heat capacity can prolong the temperature control duration.This paper has a total of 69 pictures,9 tables and 112 references. |
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