عنوان مقاله [English]
نویسنده [English]چکیده [English]
Various methods have been proposed for the analysis of underground excavations ventilation network, including manual and computer methods. The condition of selecting the type of methods depends on the network analysis. If the purpose of the analysis of underground excavations ventilation network is to investigate the effect of one or more fans, in this case, it is better to use computer method that is based on mathematical approximate methods. Several mathematical approximate methods are presented such as Hardy Cross method and its corrected models, Newton-Raphson technique and linear analysis. It is more common to use Hardy Cross method in underground excavations software packages. Accordingly, in this paper, a study has been carried out based on the Hardy Cross method for faster convergence to the final solution, which has ultimately led to presenting Hardy Cross conflation model.
Underground excavations ventilation design is made based on preparing of underground excavation map, identification of branches and injunctions in ventilation network, calculation of mine resistance for any of branches, calculation of air flow quantity for any of branches, calculation of pressure loss for any of branches, calculation of natural ventilation, network adjustment, selection of regulator doors and selection of main fans. Various methods have been presented such as manual and computer methods for the analysis of underground excavations ventilation network. The choice of analysis method depends on the purpose of ventilation network analysis.
Methodology and Approaches
The analysis of underground excavations ventilation network is carried out based on mathematical approximate methods. These methods are based on injunction rules that consider a supposition flow quantity for any of branches. Based on ventilation network fans and mathematical approximate equations, the error for any ring in ventilation network is calculated, and then, supposition flow quantity is corrected. Based on mathematical equation, correction operations of air flows quantity are repeated until calculation of accuracy become equal or bigger than calculation error. The most common mathematical methods are the Hardy Cross method and its corrected forms in the analysis of ventilation network. The Ventsim software has been presented on the basis of the Hardy Cross method. This software is one of the most famous software packages in the analysis of ventilation network.
Results and Conclusions
The most common mathematical method in the analysis of ventilation network is the Hardy Cross method. Convergence to the final solution in this method depends on the supposition flow quantity, the direction of supposition flow and the arrangement of ring selection.
The fourth and fifth stages of the solution stages of the Hardy Cross equation are more important than the other stages. In this method and its corrected methods, these two stages are calculated separately. This issue is one of their defects that causes delay in finding the final solution. Therefore, the Hardy Cross conflation method is presented for removing the defect of the Hardy Cross method and their corrected forms. The calculations in the Hardy Cross conflation method are based on the conjugate solution of the fourth and fifth stages. This conflation model can have faster convergence for finding final solution. This conflation method can decrease the number of iterations or calculations to 50 percent.