Auxiliary Fans Research Articles

DLSU Initiatives and Challenges: Energy & Climate Change

De La Salle University is committed to reducing its impact on the environment and to promoting positive action that will help reduce its carbon footprint. In its vision-mission, it emphasizes the need to be “attuned to a sustainable earth.” This paper presents the different initiatives and challenges faced by the university, especially while still in a global pandemic. A number of initiatives have been undertaken to promote energy efficiency in campus operations and climate action, particularly regarding reducing greenhouse gas emissions. However, facing the COVID-19 pandemic and preparing campus operations for the gradual resumption of face-to-face classes have presented new challenges moving into the next normal. The need to address health and safety concerns has resulted in increased consumption of electricity. Challenges are experienced particularly in ensuring improved indoor air quality as well as allowing indoor-outdoor air exchange. The setting up of (a) air purifiers and/or additional auxiliary fans in high foot-traffic areas, (b) installation of HEPA filters and UV-C lamps into HVAC systems, (c) extended use of air conditioning units to allow purging of air before and at the end of activities, and (d) the opening of air exchange dampers in the University’s HVAC systems, are all expected to result in increased demand for electricity.

Auxiliary ventilation systems in mining and tunnelling: Air leakage prediction and system design to optimize the energy efficiency and operation costs

The excavation of tunnels and mining roadways requires auxiliary ventilation systems to dilute the noxious gases from blasting and diesel engines and provide a safe environment for workers. Therefore, axial fans and ducting systems are generally installed to supply the required airflow rate to the working face. Due to the air leakage, the airflow rate varies along the ventilation duct and the design of the ventilation system is complex when leaky ducts are used. Thus, to ensure the required airflow rate at the working face, a proper sizing of the ducting system and auxiliary fan must be carried out. In this paper, analytical and CFD numerical models have been conducted to investigate auxiliary ventilation systems considering different qualities of the ventilation ducts. A forced duct of 0.6 m in diameter and 200 m long in a 14 m2 cross section mining roadway has been selected to predict the pressure drop and the air leakage along the duct. In addition, the power of the fan and the energy consumption have also been studied in the analytical models to optimize the energy efficiency and ventilation costs. The results obtained show that the power of the fan can be reduced by 74% if a duct 0.8 m in diameter is installed. Good agreements were obtained between the numerical approach and the analytical results. Finally, novel nomograms have been developed to design the ducting system and the auxiliary fans and estimate the energy consumption as a function of non-dimensional variables. Duct diameters between 600 and 2400 mm and tunnel lengths up to 4000 m can be selected to design the auxiliary ventilation circuits optimizing the operation costs.

Mine auxiliary fan in the form of an intelligent mechatronic module

Introduction. High-quality ventilation of underground workings is an important condition for safe and accident-free mining. Research on aerological situation control in work areas is ongoing, but the problem of creating reliable adaptive ventilation systems for shafts and mines remains urgent despite the progress made. In course of excavation, the system of workings on the horizon develops a highly complex structure. Auxiliary ventilation is often the only way to achieve high-quality air exchange in the working area. Methods of research. To continuously provide the working area with an estimated amount of fresh air, as well as to intensify ventilation if the concentration of toxic contaminants is increased, mine auxiliary fans (MAF) are used. The best way to improve MAF environmental and economic efficiency is to automatically control the fan capacity. Results and analysis. The program embedded in the programmable logic controller (PLC) provides for comparing the transmitters readings and the aerological situation allowed by the parameters as well as making a decision on changing the fan capacity. If the change is required, the PLC sends an appropriate command to the controller to adjust the fan engine speed. The MAF scheme is simplified if the blind drift is straight because the transmitter is in the line of sight of the receiver and there is no need for a repeater. The UMP design is of a minimal complexity when the mine working is straight and the control task is limited to ensuring constant air flow supplied to the bottom-hole zone. Out of all the data devices, only the flow transmitter remains in the circuit, while the repeater and PLC are excluded. It should also be noted that during the entire period of tunneling, the fan of an unregulated MAF creates an excess power consumption, therefore consuming more electricity than the fan of an intelligent mechatronic module (IMM). Conclusions. Conversion of MAF to IMM will provide the required amount of fresh air to the bottom-hole zone increasing the safety of miners. Real-time control of IMM capacity will significantly reduce energy consumption and create favorable conditions for optimizing ventilation according to the “price-quality” criterion.

Reducing external air leakage at the main ventilation unit of the mine

Purpose. To increase the efficiency of mine ventilation by reducing external leaks through the ventilation shaft construction. To achieve this goal, it is necessary to solve the following tasks: - to analyse the existing methods for reducing external leaks through the ventilation shaft components; - consider the possibility of using a counteracting fan to unload the main fan from external leaks; - to establish the mutual influence of the main and counteracting fans during their joint operation; - to develop a methodology for determining the operating mode of the auxiliary fan in which external leaks are stopped in full. Methodology. To accomplish the set tasks, the analysis of the existing methods for combating external leaks in the main fan of the mine was carried out; a mathematical model was developed for controlling the ventilation modes of the main and auxiliary fans during their joint operation. Based on the mathematical model, the degree of mutual influence of the fans on each other was studied, a technique was developed for determining their mode, in which the mine jet in full volume enters the main fan, and external leaks are stopped by the auxiliary fan. Findings. A mathematical model for controlling mine ventilation and stopping external leaks in the ventilation shaft elements has been developed using the methods for planning industrial experiments; the degree of mutual influence of the fans on each other has been established; a method has been developed for determining the mode of their joint operation, in which the main fan is not loaded with external leaks. Originality. The degree of mutual influence of the main and auxiliary fans during their joint operation has been determined. The conditions are studied under which the mine jet enters the main fan, while external leaks occur to the auxiliary fan. Practical value. The studies conducted make it possible to separate external leaks from the main stream coming out from the mine, which increases the safety of work and reduces the cost of ventilating the mine.

Comparative study on the thermal characteristics of natural draft wet cooling tower with internal and external auxiliary fans

Auxiliary ventilation is an innovative approach for strengthening the thermal performance of natural draft wet cooling towers, which can be implemented with internal and external fans. In this study, a three-dimensional numerical model for cooling tower with these fans is established, with consideration of the existence or absence of air deflectors. To comparatively study the thermal performance of the above cooling towers, some critical parameters such as the air mass flow rate and circulating water temperature drop are computed, and the airflow and water temperature field are also investigated. Results manifest that external fans can enhance the air mass flow rate greater than internal fans under various crosswind velocities, while they are more effective in increasing the water temperature drop under a lower and a higher crosswind velocity, with a maximum increment of 8.5% and 10.0%, respectively. The addition of air deflectors narrows the high-velocity area, thus improving the uniformity of air distribution. The positive effect of air deflectors enhances with the increase of crosswind velocity, which decreases the water temperature drop of cooling tower with internal fans and that with external fans by 10.3% and 5.6% at most, respectively. This study can promote the engineering applications of auxiliary fans.

Directions of mine ventilation development

Introduction. Underground mining is carried out under conditions of intensive development of gas from combustion-engined vehicles and blasting operations, as well as under dust pollution and workplace temperature that violate health and safety regulations. Aerological safety provision by improving mine ventilation efficiency is therefore highly relevant. Methods of research. It is reasonable to ventilate a multi-horizon mine using an automated horizon ventilation system that is responsible for the compliance of aerological conditions in workplaces with the safety requirements and consists of centralized and decentralized blocks. Research results and analysis. The centralized block redistributes air flows between entries of a horizon. The decentralized block is a set of auxiliary fans represented by intelligent mechatronic modules supplying fresh air to the workplaces. The intellectualization of the auxiliary fan places high demands on the quality of the air duct, because the efficiency of ventilation in the workplace depends on its reliable functioning. Conclusions. Air duct made of hydraulically smooth polymer units sealed with each other allows to minimize auxiliary fan energy consumption under guaranteed supply of the required amount of air into the workplace. Horizon ventilation computer-aided control and auxiliary fans with sealed polymer air ducts will make it possible to create systems with the most advantageous combination of cost and quality

ENERGY SAVINGS IN AUXILIARY VENTILATION SYSTEMS OF UNDERGROUND MINES

Energy is a basic need for industries around the world. In recent years, electrical power costs have risen considerably and this rise is likely to continue in the future. Meanwhile, the increasing cost of ventilating mines safely and efficiently is of vital importance. Ventilation on demand has the potential to optimize electrical consumption while maintaining the safety of mines. This paper investigates the energy efficiency enhancement through ventilation on demand in underground mines by installing variable speed drives on the auxiliary mine ventilation fans to provide variable airflow control. Variable speed drives are cost effective and manageable and require low maintenance. It has been estimated that a total electrical energy saving of 324,300 kW, or 53%, can be achieved in 1 year by using variable speed drives. Therefore, it is possible to reduce CO2 emissions by 155.6 tons per year with a simple payback period of 5 months 220 days.

Research on the Fault Diagnosis Method of Mine Fan Based on Sound Signal Analysis

The underground local fan and auxiliary fan also play a vital role in the underground air quality, compared with the system fan. However, the number of underground local fans and auxiliary fans is large and widely distributed, which is disadvantageous to adopt the same method of online monitoring and fault diagnosis method as the system fan. In order to find a new fault diagnosis method, which is cost-effective and reliable, this paper proposes a fault diagnosis method based on sound signal. It analyzes the source of fan noise and studies the overall scheme of mine fan fault diagnosis expert system based on sound signal. The fault expert system consists of four parts: signal acquisition and noise elimination, feature extraction, state recognition, and fault diagnosis. Its principle is briefly introduced. The denoising method of wavelet is adopted in this paper. Wavelet packet is used to extract the characteristics of sound signal, and the energy size and energy proportion of each frequency component are used as the basis of knowledge acquisition and reasoning. Through the analysis of the measured signals of the fan in the normal operating state, the feature vectors were extracted as the basis for the discrimination of the normal state after noise elimination. At the same time, the audio processing software was used to simulate the sound signals in three fault states. Then, the feature vector of the fault state is extracted, which is obviously different from that of the fan in the normal operation. As the basis of fault state analysis of the expert system, it lays the foundation for the realization of the expert system of mine fan equipment running state diagnosis.

An overview of the Nordic mine ventilation system

ABSTRACT This paper describes the ventilation system used in underground hard rock mines in Sweden and Finland, which differs in many respects from the system commonly used in other major mining countries such as Australia, Canada, South Africa, and the USA. The Nordic system utilizes auxiliary fans with a variable speed drive to distribute primary airflow to working levels instead of regulators, which are commonly used in other countries. In addition to comparing the Nordic system with the system used in other countries, this paper describes the system’s ventilation-on-demand and air conditioning, as well as ventilation regulations in Sweden and Finland. A discussion regarding the potential to use natural-assisted refrigeration in the future is also described in this paper.

Evaluating the impact of auxiliary fan practices on localised subsurface ventilation

Mines are continually expanding in size and depth, leading to an increased reliance on localised subsurface ventilation systems. The use of underground auxiliary fans is a favoured method to increase and control airflow in working areas. However, the effectiveness of auxiliary fans in this regard is not clear. This paper evaluated the performance of these underground fan systems in four different South African deep-level gold mines. A total auxiliary fan system efficiency of 5% was found across six systems, with the average fan efficiency of 33 fans at 38%. The results showed that these fans deviate significantly from their design operating points. Therefore, there are significant shortcomings in current underground fan practices. Our detailed investigations led to the conclusion that the assemblage of underground auxiliary fan systems results in significant energy inefficiencies. Therefore, maintaining good underground fan practice such as optimal fan selection, ducting design and maintenance is crucial for the efficacy of a mine ventilation network.

Correlating variability of the leakage characteristics with the hydraulic performance of an auxiliary ventilation system

Ventilation is one of the key factors in controlling underground working environment by providing sufficient amount of fresh air for breathing, dispersing harmful gasses and dust and to some extent for heating/cooling. Insufficient airflow is dangerous for the working face and can lead to fatalities. Duct leakage is the most common reason for the insufficient fresh air in underground working and has been the subject of many studies in the literature. However, the main focus has been on ascertaining its impact on the ventilation requirements of the underground environment. This study aims to identify key variables associated with duct leakage that significantly impacts the power consumption levels of auxiliary fans which form an integral part of the underground ventilation system. A three-dimensional Computational Fluid Dynamics (CFD) modeling approach is undertaken in conjunction with Monte Carlo simulations and multiple regression analysis to quantify the effect of duct leakage on the fan operating point and discharge flow rate towards the working face. Various cases involving the positioning, orientation, and size of the rupture in the ventilation duct are simulated, and their respective effects on fan operating point and power levels are determined. Results indicate that the operating point of a fan for ventilation ducts is strongly correlated with the position and size of the rupture, resulting in reduced delivery of ventilation air towards the working face for different levels of fan power consumption.

Causes Of Low Efficiency Of Combined Ventilation System In Coal Mines In Resolving The Problem Of Air Leaks (Inflows) Between Levels And Surface

The paper discusses the problem of the underground mining safety control. The long-term air intake to coal accumulations is reviewed as one of the reasons of endogenous fires during mining. The methods of combating air leaks (inflows) in order to prevent endogenous fires are analyzed. The calculations showing the discrepancy between the design calculations for the mine ventilation, disregarding a number of mining-andgeological and mining-engineering factors, and the actual conditions of mining are given. It is proved that the conversion of operating mines to combined (pressure and exhaust) ventilation system in order to reduce the endogenous fire hazard of underground mining is unreasonable due to impossibility of providing an optimal distribution of aerodynamic pressure in mines. The conversion does not exclude the entry of air into potentially hazardous zones of endogenous fires. The essence of the combined application of positive and negative control methods for the distribution of air pressure is revealed. It consists of air doors installation in easily ventilated airways and installation of pressure equalization chambers equipped with auxiliary fans near the stoppings, working sections and in parallel airways.The effectiveness of the combined application of negative and positive control methods for the air pressure distribution in order to reduce endogenous fire hazard of mining operations is proved.

Experimental Study on the Noise Characteristics Regarding Axial Auxiliary Fans and the Noise Reduction Performance of Mufflers

High-intensity noise not only hurts body and mental health of workers, but also covers sound signs of accidence. To increase the sound absorption and noise reduction performance of axial auxiliary fan noise silencers, the noise strength and frequency distribution of the ambient medium casing of an FBYNo3.0/2.2 (II) axial auxiliary fan were investigated. The noise characteristics at the inlets and outlets were analyzed. Based on this study, a new auxiliary fan bell-type muffler was designed, and its noise elimination ability was tested. The results showed that on the surface of the auxiliary fan casing, the noise intensity exhibited a “V” font distribution in that the maximum noise intensity was located in the air outlet and the minimum noise intensity was located in the middle part of the fan. Mid- and low-frequency noise was presented primarily at the outlets. However, intermediate- and high-frequency noise was presented primarily at the inlets. The muffler performance test revealed that the installation of a muffler can dramatically reduce the intensity of the auxiliary fan’s noise. The mean decrease in noise intensity for various positions was 14 dB (A). The noise elimination rate of the muffler was over 15 %. This decreased level of noise was less than the Chinese national standard for maximum noise intensity, 85 dB (A). In addition, optimizing the noise frequency of the inlets and outlets by decreasing the intermediate- and high-frequency noise of the inlets and the intermediate- and low-frequency noise of the outlets can lead to the greatest noise reduction.

대단면국내석회석광산용저풍압국부선풍기개발연구

At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.

Development of underground mine monitoring and communication system integrated ZigBee and GIS

An automated underground mine monitoring and communication system based on the integration of new technologies is introduced to promote safety and health, operational management and cost-effectiveness. The proposed system integration considering Wireless Sensor Network (WSN) assisted Geographic Information System (GIS) enables to monitor and control underground mining applications from surface office. Based on the capabilities of WSNs, ZigBee network is adapted for near real-time monitoring, ventilation system control and emergency communication in underground mine. ZigBee nodes were developed to sense environmental attributes such as temperature, humidity and gases concentration; switching ON and OFF ventilation fans; and texting emergency messages. A trigger action plan for monitored attributes above normal and threshold value limits is programmed in the surface GIS management server. It is designed to turn the auxiliary fans on remotely or automatically in orange condition and sending evacuation messages for underground miners in unsafe (red) condition. Multi-users operation and 3D visualisations are other successful achievements of the proposed system for the underground monitoring and communication.

Optimizing arrangement of air distribution controllers in mine ventilation system

The authors report the research results on the upgrading of the automated design planning of the underground mine ventilation system by using modern mathematical methods with the discussion of the perspective application of the genetic methods to analyze alternative ventilation systems at the design stage. The integrated variants of the optimized number of auxiliary fans and brattices, their arrangement and parameters at new Olenii Ruchey and Partomchorr mines.

Statistical model for the volume rate reaching the end of ventilation duct

Auxiliary ventilation is used to ventilate dead-ends of the drivages, and the most common method employed is to use auxiliary fans and ducting. In order to provide a safe and comfortable environment, it is necessary to provide sufficient air to the working areas. The optimum design of auxiliary ventilation systems may be difficult owing to the methods used in the design of such systems that require complex calculations. In this study, by evaluating data gathered from Turkish Hardcoal Enterprises, a predictive model of the volume flow rate reaching the end of a leaky ventilation duct for a simple auxiliary ventilation system was developed using multiple regression analysis. The independent variables that enter the regression were chosen as duct diameter, fan flow output, fan operating pressure, frictional pressure drop, duct length, duct resistance, and resistance coefficient of leakage paths. The coefficient of determination ( R 2) obtained for the predictive model was 0.931, and the residual analysis indicated that the model was statistically acceptable. Also, by using the two-sample t-test, it was shown that the developed regression model was consistent with the results obtained from another data set not included in the derivation of the presently developed regression model.

The influence of ventilation variables on the volume rate of airflow delivered to the face of long drivages

Auxiliary ventilation is performed by carrying intake or return air in ducts. The complete elimination of air leakage from or into the ducting system is impossible due to duct quality and numerous joints in ducting system. The auxiliary ventilation systems for long drivages often require the use of multiple fans. Fans are installed in series and separated from each other in fixed or variable lengths. There are many methods proposed for the analysis air flow problems in leaky ducts. Due to the lengthy calculations, computers are often needed to conduct the analyses. In this study, a method known as “series–parallel combination of the duct and leakage path” has been introduced and a computer program has been developed based on this method. In order to design the conditions of an auxiliary ventilated drivage, in situ measurement have been made in Western Lignite Enterprises (GLI) OMERLER underground coal mine (Turkey) and the related data necessary for this study was collected. The presently developed program was tested using these data, and it was found that the measured and calculated values are quite close. The effective operational parameters governing auxiliary ventilation have been investigated and the effects of these variables on the volume rate of air flow reaching long drivage face have been examined by using linear regression analysis. Finally, it was concluded that the increase of duct diameter has prime importance in achieving the adequate air flow to the face and that for the auxiliary fans considered in this study the selection of fan does not greatly affect the volume rate reaching the face in a long duct line.

Uncontrolled recirculation in auxiliary ventilation with fans in series along the duct

When fans are placed in series at intervals along a duct line it is possible for uncontrolled recirculation of air to take place if there is leakage into or out of the duct. On the assumption that hazardous conditions can develop, many government regulations either forbid the use of auxiliary fans in series along the duct line or specify the installation of auxiliary fans in such a way that uncontrolled recirculation is avoided. The degree of recirculation depends upon the positions of the fans and the leakage characteristic of the duct line. Through an illustrative realistic example, the following advantages of designing auxiliary ventilation systems with recirculation have been determined: (1) the number of fans required becomes less in bad installations, hence reduced capital and power costs; (2) in good installations, the number of fans required may not become less but the fresh airflow at the face improves; (3) the velocity of airflow at the face becomes more, hence the rate of dilution and enhanced mixing; (4) the climatic conditions at the face improve. With the availability of systems for monitoring air volume flow rates and concentrations of pollutants, recirculation can be practised with confidence.

Pompes de chaleur à transferts thermiques sans auxiliaires, à convection naturelle et rayonnement

With many conventional heat pump systems the energy absorbed by auxiliary equipment (fans, defrosters, pumps) can be higher than the power used by the compressor. For example, with a particular air-air heat pump system the annual energy consumption of the compressor and its crankcase heater is 11 240 kWh, whilst 21 501 kWh of energy are consumed by auxiliary fans, the defrost unit, back-up heating and system heat losses. Some savings can be made by monitoring the interior unit fan to correspond to the running time of the compressor or by increasing the size of the heat pump in order to reduce back-up heating, but the latter solution has proved to be costly. Laboratory experiments since 1976 have been to reduce power consumption of auxiliaries, particularly air-air and air-water systems, by using a solar collector as the heat pump evaporator. The collector is made up of flat plates oriented in such a manner as to receive direct solar radiation, with both faces of the plates absorbing energy from the surrounding air by natural convection. The faces of the plates exposed to solar radiation are preferably painted black, but other colours with a low coefficient of reflection (eg brown, brick red, dark green, etc.) can be used if the evaporator-collector is to be architecturally pleasing. Glazing is not necessary, as is usually the case with solar panels. The collector-evaporator plates, and associated piping, are precharged with refrigerant and ready for connection to the heat pump circuit. A heat pump equipped with this collector-evaporator will provide an annual energy saving of 30% as compared to a standard air—water system. Additional benefits are no defrosting cycles, simplified installation, greater operational reliability, and an increased system COP. A table sets out the performance parameters of this system to show the incidence of back-up solar energy during the months of lesser solar radiation, ie outside the months of June to September, eg the COP during daylight hours (a minimum of about 7 h in December, to a minimum of 14 h in May) averages out at 3.89, and 3.27 during nocturnal hours. The article also describes a water heating system (200 and 300 I) using this collector-evaporator, an air-air heat pump with static (no forced ventilation) heat exchangers, and an air-water system using a static evaporator which will provide a 25% energy saving over its conventional counterpart.