This paper describes a new practical method for predicting environmental airflow-conditions, such as temperature and enthalpy, in underground ventilation networks. The calculation code “MIVENA” for mine ventilation networks has developed by authors using with a nodal head method and the temperature-humidity prediction method. The equations and schemes fitted to the network calculations are presented clearly as a general form. The system was mostly compared with Amano et al.'s system and differences between two systems are discussed.
The prediction method is that the environmental airflow-conditions on nodes are calculated from inlet nodes to downstream nodes and ones on the fan node can be calculated at last. The environmental conditions of inflow airstream on airways connected to a node are calculated from upstream to downstream with a kind of one dimensional numerical-difference methods by dividing the airways to 5 m long spans before the calculations of the node.
The temperature and humidity on nodes consisting of the recirculation loop can be calculated by using a function which indicate a approximation degree of the calculation result. When absolute humidity in airflow becomes larger than saturation absolute humidity on airways or nodes, the methods and calculation schemes for revisions of temperature and humidity are also presented. These methods are effective for calculations on exhaust airways which are influenced by auto-expansion with temperature reduction.
The present calculation system was successfully applied to the Amano et al.'s network example, the Ezuri Mine and the Fukasawa Mine run by Hanaoka Mining Co. LTD. Fan driving maps for main fans controlled by thylisters, which indicate the total inlet airflow-quantity on several seasons against the thylister frequency, were made to find out the optimum driving thylister frequency on each season.