Novel Approach to the Energy Analysis of Mine Cooling Strategies

The extraction of minerals and coal at increasing depth, employing higher-powered, mechanized machinery to increase production levels imposes an increased burden on the ability to maintain an acceptable mine climate. Any deterioration in the mine climate within working zones may adversely affect the health and safety of the workforce. The combination of the optimal design of the mine system layout, together with the selective application of suitable ventilation and cooling systems, may be used to control the climate within working zones. The adoption of mechanical cooling within mines is an expensive process in terms of both capital and operating costs. Therefore, as mechanized mining takes place at increased depth, the need to maintain or improve the mine climate becomes more expensive. Consequently, to decrease overhead costs, reduce energy consumption and meet current and future environmental obligations, it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. To perform this analysis it is necessary to have a good understanding of the energy balances governing both the operation and utilization of a cooling system. This paper introduces the application of a novel approach to energy analysis of mine cooling systems, with a combination of the concepts of exergy and composite curves. These methods are used extensively throughout chemical and process industries to increase energy efficiency and reduce capital and operating costs. An outline of the methods employed in the application of these techniques to the energy analysis of a mining cooling system is presented

Reconciling Gaussian plume and Computational Fluid Dynamics models of particulate dispersion

Computational Fluid Dynamics (CFD) is increasingly used to model particulate dispersion in situations where Gaussian Dispersion models are inappropriate or inaccurate. However, there is evidence which indicates that many CFD models under-predict lateral plume spread. This paper aims to address this by imple- menting a strategy which incorporates wind direction variability into CFD models using a formulation which is also used in the UK-ADMS plume spread module. In the present work, a series of CFD simulations are run at various wind angles. The outputs from these simulations are weighted using a Gaussian probability density function and combined to produce a plume. The standard k−ε model has been employed to solve the RANS equations of the flow field for stable, neutral and unstable atmospheric stabilities, coupled with the Lagrangian Particle tracking model to model dispersion. By comparing the CFD accretion profiles to UK-ADMS dry deposition results, it is observed that the proposed modelling methodology produces lateral spreading of the plume which is comparable to that obtained using UK-ADMS. However, the Lagrangian integral time scale constant, c L , which governs the influence turbulence has on the dispersion, must also be modified to bring absolute values of accretion rates in line with those observed in UK-ADMS

Validation of Computational Models of Auxiliary Ventilation Systems with Experimental Data

This paper reports the interim findings of a research program whose objective is to determine whether Computational Fluid Dynamic (CFD) models can be employed to accurately predict the airflow patterns within rapid development headings. In particular, the project aims to investigate the optimum set back distances for the ducts in order to adequately ventilate the face of the drivage. To validate the accuracy of the CFD model simulations measurements were obtained from a series of experiments performed on both scale models and within a full-scale surface gallery. The experimental scale-modeling program included making a series of pressure measurements across the face of the model for equivalent forcing duct setback distances of 5, 10 and 15 m (16, 33 and 50 ft). This pressure data was then plotted as contour plots and compared with the corresponding CFD predictions. A series of full-scale auxiliary ventilation trials were performed within a modified surface gallery. Three-dimensional velocity measurements were taken across a number of cross-sections using an ultrasonic anemometer. Velocity measurements were obtained for three forcing duct setback distances and for a typical force-exhaust overlap configuration

A Review of Primary Mine Ventilation System Optimization

Within the mining industry, a safe and economical mine ventilation system is an essential component of all underground mines. In recent years, research scientists and engineers have explored operations research methods to assist in the design and safe operation of primary mine ventilation systems. The main objective of these studies is to develop algorithms to identify the primary mine ventilation systems that minimize the fan power costs, including their working performance. The principal task is to identify the number, location, and duty of fans and regulators for installation within a defined ventilation network to distribute the required fresh airflow at minimum cost. The successful implementation of these methods may produce a computational design tool to aid mine planning and ventilation engineers. This paper presents a review of the results of a series of recent research studies that have explored the use of mathematical methods to determine the optimum design of primary mine ventilation systems relative to fan power costs

TE INTEGRATION OF WATER HYDRODYNAMICS MODELLING AND REMOTE SENSING DATA TO IMPROVE THE WATER CIRCULATION OF LAKE MANZALA, EGYPT

This paper presents the preliminary results of the application of the ocean model (FVCOM) to replicate the hydrodynamic flows experienced within Lake El-Manzala, Egypt. The construction of this model is used to characterize the ecosystem of this shallow brackish lake and assess a range of sustainable water management strategies. Lake El-Manzala is the largest of the Egyptian shallow coastal lakes on the fringe of the Mediterranean Sea. The lake currently supports 30% of the fresh water fish farm production of Egypt. In recent years the aquatic health of the lake has significantly deteriorated due to an increase in the contamination of the lake by polluted inflows and over intensive aquaculture. The focus of this study is to develop a model that may be employed to investigate the causes, effects and potential solutions to the pollutant loads imposed on the lake. The model has been used to study the hydrodynamic effect that a 40% reduction in the polluted drain water inflows to the lake due to a diversion of this water towards the Sinai for land development. This study concluded that in the western zone of the lake this action slightly changed the magnitude and direction of the water flows and an increase in the salinity levels. Several other lake management scenarios were proposed and the environmental effects on the lake water quality are under investigation. It is concluded that the hydrodynamic models developed may be used to study the cause and effects of other aquatic pollution problems and permit the investigation of potential engineering solutions to improve water quality management

An improved continuous compositional-spread technique based on pulsed-laser deposition and applicable to large substrate areas

A new method for continuous compositional-spread (CCS) thin-film fabrication based on pulsed-laser deposition (PLD) is introduced. This approach is based on a translation of the substrate heater and the synchronized firing of the excimer laser, with the deposition occurring through a slit-shaped aperture. Alloying is achieved during film growth (possible at elevated temperature) by the repeated sequential deposition of sub-monolayer amounts. Our approach overcomes serious shortcomings in previous in-situ implementations of CCS based on sputtering or PLD, in particular the variations of thickness across the compositional spread and the differing deposition energetics as function of position. While moving-shutter techniques are appropriate for PLD-approaches yielding complete spreads on small substrates (i.e. small as compared to distances over which the deposition parameters in PLD vary, typically about 1 cm), our method can be used to fabricate samples that are large enough for individual compositions to be analyzed by conventional techniques, including temperature-dependent measurements of resistivity and dielectric and magnetic and properties (i.e. SQUID magnetometry). Initial results are shown for spreads of (Sr,Ca)RuO$_3$.Comment: 6 pages, 8 figures, accepted for publication in Rev. Sci. Instru

On the de Haas-van Alphen effect in inhomogeneous alloys

We show that Landau level broadening in alloys occurs naturally as a consequence of random variations in the local quasiparticle density, without the need to consider a relaxation time. This approach predicts Lorentzian-broadened Landau levels similar to those derived by Dingle using the relaxation-time approximation. However, rather than being determined by a finite relaxation time $\tau$, the Landau-level widths instead depend directly on the rate at which the de Haas-van Alphen frequency changes with alloy composition. The results are in good agreement with recent data from three very different alloy systems.Comment: 5 pages, no figure

Field Emission and Nanostructure of Carbon Films

The results of field emission measurements of various forms of carbon films are reported. It is shown that the films nanostructure is a crucial factor determining the field emission properties. In particular, smooth, pulsed-laser deposited amorphous carbon films with both high and low sp3 contents are poor field emitters. This is similar to the results obtained for smooth nanocrystalline, sp2-bonded carbon films. In contrast, carbon films prepared by hot-filament chemical vapor deposition (HE-CVD) exhibit very good field emission properties, including low emission turn-on fields, high emission site density, and excellent durability. HF-CVD carbon films were found to be predominantly sp2-bonded. However, surface morphology studies show that these films are thoroughly nanostructured, which is believed to be responsible for their promising field emission properties

Positive Impact of Increases in Condom Use among Female Sex Workers and Clients in a Medium HIV Prevalence Epidemic: Modelling Results from Project SIDA1/2/3 in Cotonou, Benin

Background A comprehensive, HIV prevention programme (Projet Sida1/2/3) was implemented among female sex workers (FSWs) in Cotonou, Benin, in 1993 following which condom use among FSWs increased threefold between 1993 and 2008 while FSW HIV prevalence declined from 53.3% to 30.4%. Objective Estimate the potential impact of the intervention on HIV prevalence/incidence in FSWs, clients and the general population in Cotonou, Benin. Methods and Findings A transmission dynamics model parameterised with setting-specific bio-behavioural data was used within a Bayesian framework to fit the model and simulate HIV transmission in the high and low-risk population of Cotonou and to estimate HIV incidence and infections averted by SIDA1/2/3. Our model results suggest that prior to SIDA1/2/3 commercial sex had contributed directly or indirectly to 93% (84–98%) of all cumulative infections and that the observed decline in FSWs HIV prevalence was more consistent with the self-reported post-intervention increase in condom use by FSWs than a counterfactual assuming no change in condom use after 1993 (CF-1). Compared to the counterfactual (CF-1), the increase in condom use may have prevented 62% (52–71%) of new HIV infections among FSWs between 1993 and 2008 and 33% (20–46%) in the overall population. Conclusions Our analysis provides plausible evidence that the post-intervention increase in condom use during commercial sex significantly reduced HIV prevalence and incidence among FSWs and general population. Sex worker interventions can be effective even in medium HIV prevalence epidemics and need to be sustained over the long-term

The South West Area Mesothelioma and Pemetrexed trial - A multi-centre prospective observational study evaluating novel markers of chemotherapy response and prognostication

Background:Robust markers that predict prognosis and detect early treatment response in malignant pleural mesothelioma (MPM) would enhance patient care.Methods:Consecutive patients with MPM who were considered fit for first-line chemotherapy were prospectively recruited. Patients of similar performance status opting for best supportive care were included as a comparator group. Baseline and interval CT, PET-CT and serum markers (mesothelin, fibulin-3 and neutrophil–lymphocyte ratio (NLR)) were obtained, and patients followed up for a minimum 12 months.Findings:Seventy-three patients were recruited (58 chemotherapy/15 comparator arm). Baseline TGV (total glycolytic volume on PET-CT) was an independent predictor of worse overall survival (OS) (P=0.001). Change in interval TGV(baseline/after two cycles of chemotherapy) did not predict OS or chemotherapy response on CT. Baseline NL