Heat-transfer enhancement and optimization design of a roadway with typical angles using field synergy theory

Heat damage in underground mines has always been a difficult problem that troubles mining work. Many scholars are committed to studying its heat-transfer mechanism, exploring the heat-transfer characteristics between airflow and the surrounding rock under different influencing factors, so as to lay a theoretical foundation for the development of underground cooling technology. However, there is no research on the essence of convective heat transfer. In this study, we conducted numerical simulations of roadway models from different acute angles under the guidance of field synergy theory, explored the synergy between the velocity field and temperature-gradient field in the process of convective heat transfer, and obtained the roadway model with the least heat transfer. This should provide theoretical guidance for the selection of excavation plans for roadways in the underground mining process. This study first analyzed the influence of different typical angles of the roadway on the heat transfer performance of the airflow and the surrounding rock when the acute angles were 60°, 75°, and 90°, respectively, and also analyzed the influences of the Reynolds number and roadway angles on the heat transfer according to the field synergy theory, which revealed that the 90° roadway had the least heat transfer. Then, based on the 90° roadway model, 8 different types of turning radius (R) were added to the corners, and their heat-transfer performance and comprehensive performance were explored based on the field synergy theory. The results indicated that when R = 3.5 m, the convective heat transfer between the airflow and the surrounding rock was the least; when R = 4 m, the resistance of the airflow was the smallest; when R = 3.5 m, the comprehensive performance was the best, with an average comprehensive performance improvement of 2.7% compared to the 90° roadway. Therefore, in underground excavation operations, an excavation path with a turning radius of 3.5 meters should be selected.