Numerical simulation of ventilation air flow in underground mine workings

In recent years, Computational Fluid Dynamics, CFD, has been commonly utilized in the mining industry to model the fluid flow behavior in underground mine workings. This paper uses CFD modeling to simulate the airflow behavior in underground crosscut regions, where brattice sails are used to direct the airflow into these regions. Brattice sails are cost effective ventilation control devices for temporary or permanent use in underground mining. They can be used to deflect air into the unventilated areas such as crosscut regions. Their design and installation is a fundamental issue for maintaining a sufficient supply of fresh air and achieving effective air circulation and contaminant removal. At the same time, they should have little impact on the mine ventilation system. This paper presents the results of a two-dimensional CFD model, which examines the effects of brattice length on fluid flow behavior in the crosscut regions. The results of this study will assist in understanding the ventilation air behavior and in determining the optimum size of brattice curtain (sails), which provide a highly effective contaminant removal from the unventilated mine areas. This, in turn, helps the mine ventilation designers to meet the mine safety requirements

The effects of orientation of an inclined enclosure on laminar natural convection

Natural convective laminar flow is numerically investigated in a two-dimensional and square enclosure at various angles of inclination respect to horizontal. Two adjacent walls of the enclosure are insulated and the other two are kept at different temperatures. The influence of Rayleigh number representing the effects due to the differential heating of the enclosure walls as well as the effect of inclination angle on natural convection flow are studied. The flow field and isothermal lines show different patterns at high Rayleigh numbers. The average Nusselt number, maximum stream function and average temperature appear to be a little affected by the inclination angle at low Rayleigh numbers. However, as the Rayleigh numbers rises, these parameters behave differently at various inclination angles. In this study, the effects of inclination on the temperature along the centerline of the enclosure and the local Nusselt number along the cold wall are also examined. The results show negligible effects of inclination angle at low Rayleigh numbers and considerable effects at high Rayleigh numbers

Monetary Savings Opportunities of Electronic Blast Initiation Systems

There are several blast initiation systems available on the market; these form a large component of the performance of each blast. Each available system has its own advantages and disadvantages which can affect the fragmentation of each blast, which in turn can affect downstream processes such as digging and hauling of material. This study was conducted to determine if there were monetary savings opportunities due to an increase in fragmentation (and hence downstream productivity) due to the use of an electronic blast initiation system over a pyrotechnic blast initiation system. It was completed using data collected from an open cut metallurgical coal mine in Queensland that agreed to be used as a case study. Statistical analysis of data was completed in order to identify if downstream productivity had increased, with the results from this being used to calculate potential savings opportunities. The results of this study suggest that there are increases in productivity during loading and hauling, which lead to significant savings opportunities when using an electronic blast initiation system

Computational analysis of magnetohydrodynamic natural convection in a square cavity with a thin fin

A numerical study of laminar natural convection in a square cavity with a thin fin that is under the influence of a uniform magnetic field is presented. The side walls of the cavity are kept at different temperatures and the horizontal walls are thermally insulated. An Adaptive Network-based Fuzzy Inference System (ANFIS) approach and an Artificial Neural Network (ANN) approach are developed, trained and validated using the results of Computational Fluid Dynamics (CFD) analysis. The effects of pertinent parameters on fluid flow and heat transfer characteristics are studied. Among these parameters are the Rayleigh number (103≤≤;106), the Hartmann number (0≤&Ha;≤;100), the position of the thin fin (0.1≤ Y p≤) and the length of the thin fin (0≤Lp≤0.8). The results show that ANFIS and ANN can successfully predict the fluid flow and heat transfer behaviour within the cavity in less time without compromising accuracy. In most cases, ANFIS can predict the results more accurately than ANN

Large-scale study of the effect of wellbore geometry on integrated reservoir-wellbore flow

Extraction of coal seam gas (CSG) prior to mining is crucial for reducing the potential risks of gas outburst and explosions during underground coal mining as well as gas production purposes. Many numerical and experimental studies have been carried out to identify the factors affecting the gas productivity. These factors include coal properties, gas content and wellbore geometries. Two different flow conditions determine the gas production efficiency: The gas flow inside the wellbore injected from wall, and the flow through porous coal medium. The full understanding of simultaneous flow of fluids through reservoir and wellbore is critical for analysing the reservoir behaviour. However, previous studies examined the flow of these fluids separately. In this research, a large scale three-dimensional model for simulation of integrated reservoir-wellbore flow is developed to study the effect of wellbore geometry on flow characteristics and wellbore productivity. Four different wellbore diameters of 0.075, 0.10, 0.125 and 0.15 m as well as three different lengths of 50, 100, and 150 m were chosen to accomplish the parametric study of wellbore geometry. It is assumed that the wellbores were in a steady-state condition for two different single phase scenarios of water and methane gas flow. The simulation results were validated against the pressure drop models for internal single phase gas and water flow reported in the literature. The obtained results revealed that increasing the wellbore diameter led to reduction of fluid pressure in the coal seam. Regarding the effect of wellbore length, it was observed that at a specific distance from wellbore outlet, the pressure distribution is independent of the wellbore length and upstream effects. It is also shown that wellbore production could be enhanced by increasing the diameter and the length of wellbore for both gas and liquid flow. The developed integrated framework can be used further for study of any enhanced gas recovery method by changing the boundary conditions based on the physical model

A Review of patents in tyre cooling

A number of patents on tyre cooling have been reviewed with a focus on those which can be applied to earthmoving tyres for the mining industry. The mechanisms of heat transfer within the tyre carcass are introduced as well as the basic tyre structure and effects of overheating on tyre operation. The tyre cooling patents are separated into five functional groups and reviews are made based on practicality and potential for significant heat transfer. This analysis has made it evident that potential cooling effectiveness is often compromised by practicality of an invention. The patents deemed to have the most potential for cooling are those which incorporate a working fluid which undergoes a phase change to transfer heat between different regions of the wheel assembly. Finally, these inventions are also related to current research projects which aim to develop a new cooling technique and extend the working life of earthmoving tyres

Current developments and challenges of underground mine ventilation and cooling methods

The mining industry has experienced a dramatic change over the past 20 years in terms of methods and equipment as well as human resource policies. These changes have had impacts on the design of mine ventilation systems. Although feasible developments have been implemented to some extent, in some other areas ventilation planning still requires further improvements to provide a healthy work environment at a reasonable cost. The boom in energy costs has also encouraged mine ventilation designers to seek for efficient use of energy and optimization strategies. The electricity consumption by mine refrigeration plants should be reduced possibly without any adverse effects on the safety of workers. This study presents an overview of the latest techniques used by the experts to address these issues. A revision of the novel ventilation strategies and mine refrigeration methods, and their ultimate effect on efficiency and mining costs would be identified. Finally, likely future developments in the area of mine cooling are outlined

Development and utilisation of fibre optic-based monitoring systems for underground coal mines

The continuous economic growth and depleting shallow reserves have increased the number of deeper mining operations worldwide which has made safety and productivity more challenging due to the higher stresses, heat and increased gas contents. Any major improvements in safety and productivity require a reliable and real-time monitoring system that provides more comprehensive information about various processes. The current monitoring systems suffer from lack of reliability, accuracy and high capital and operating costs. Recent advancements in fibre-optic based sensing technology have introduced unique solutions for various underground coal mine applications such as health and safety, geotechnical, ventilation, borehole, mine environment and condition monitoring. This paper presents recent research, development and utilisation of this technology by a group of researchers at the University of Queensland (UQ) and CRCMining in Australia and Shandong Academy of Science in China

A 3D LBM-DEM study of sheared particle suspensions under the influence of temperature-dependent viscosity

Particle suspensions form a fundamental yet complex component of many scientific and engineering endeavours. This paper proposes a numerical coupling between the lattice Boltzmann and discrete element methods that resolves particle suspensions exposed to thermal influences due to temperature-dependent fluid viscosity and conjugate heat transfer between components. Validation of the model was performed via the study of the relative viscosity of suspensions. This numerically corroborated the proposed temperature-dependence of the relative viscosity of suspensions. The model was finally used to interrogate the macroscopic behaviour of sheared suspensions at a range of solid volume fractions. This demonstrated changes in suspension flow behaviour due to temperature related effects. Future work based on these results would examine how particle properties could be modified to exacerbate and control temperature-based phenomena potentially leading to improvements in domains such as industrial material processing and manufacture