Research on calculation and optimization method of refrigeration and cooling pipe network in high temperature mine

Adoption of centralized underground refrigeration cooling system in high-temperature mine is affected by the range of mining. The complex chilled water transmission pipeline network leads to inadequate supply of terminal cooling capacity, which significantly affects the cooling effectiveness. In order to improve the utilization of cooling capacity in mine cooling system, taken the underground refrigeration cooling pipe network of Zhaolou Coal Mine as an example. The topological model of cooling pipe network was established based on the principle of graph theory. The hydraulic basic equation was used to calculate the flow, nodal resistance and hydraulic losses of the pipe section to obtain the hydraulic characteristics of cooling pipe network. The cooling loss of chilled water transportation was determined by calculating the temperature rise of pipe network nodes. The cooling pipe network was optimized by combining the hydraulic and thermal characteristics of pipe network. The results shown that, the minimum chilled water flow was 0.001 m³/s in the working face at the end of underground cooling pipe network in Zhaolou Coal Mine. The locations with significant hydraulic losses in the pipe network were A set of Track Downhill, 7302 Transport Roadway and Central Auxiliary Transport Roadway. The system respectively supplied cooling to four working faces in the Fifth and Seventh mining areas. The total cooling loss was 1.219×10⁶ J/s, of which the cooling system in Seventh mining area accounted for 88.15%, the friction and heat transfer losses of pipe network is 5.39×10⁵ J/s and 6.805×10⁵ J/s, respectively, and the maximum temperature of chilled water at the end was 13.9 °C. The optimization method of pipeline-pump-valve inter-conditioning was proposed, the dynamic balance valve was used to maintain the chilled water flow in the range of 0.022−0.04 m³/s in the South 1 # Auxiliary Transportation Roadway and the Second Set Auxiliary Roadway, to achieve the flow stability of the end air cooler. The static balance valve was used to adjust the branch resistance of the pipe network, and the chilled water flow was increased to 0.005 m³/s at the working face. The pipe diameter of the South No.1 Auxiliary Transportation Roadway, the South No.2 Auxiliary Transportation Roadway and the Second Set Auxiliary Roadway was increased to 0.325 m, and total hydraulic loss of the pipe network was reduced from 30.93 m to 20.44 m, which was a reduction of 35%. The centrifugal pump head was adjusted to 183−195 m with a flow rate of 0.085−0.112 m³/s, which ensured efficient operation of the centrifugal pump.