Volumetric Air Flow Research Articles

Hybrid solar drying of sludge from kraft pulp mills

Abstract Sludge generated from kraft pulp mill wastewater treatment plants (WWTPs) is typically non-inert solid waste and is commonly disposed of in landfills. In this study, a novel approach for repurposing WWTP sludge from a kraft pulp mill in Brazil for energy generation was assessed. With the global cellulose market projected to reach $ 61 billion by 2033, there is a growing need for sustainable energy solutions and disposal of associated industrial byproducts. This study investigated the performance of a hybrid active solar dryer for reducing the moisture content of sludge to enhance the feasibility of sludge burning in a biomass boiler. Through rigorous experimentation and design of experiments (DOE) planning, optimal parameters for the hybrid dryer were determined, specifically, a volumetric airflow rate of 1.1 m/s and an entrance temperature of approximately 51 °C. This innovative approach not only addresses the environmental concerns associated with sludge disposal, but also contributes to the broader goal of advancing sustainable technologies in the midst of global energy challenges.

Investigation of The Blade’s Sweep Size Effect On the Air Flow Field and The Energy Efficiency of the Ceiling Fan

The ceiling fan is the most economic device to cool the residential areas and as well as commercial areas. The ceiling fan plays vital role in thermal comfort for the people in those areas. Due to recent advancement in technologies ceiling fans are become energy efficient. This paper talks about the comparison of energy efficient and changes in flow field across the user perceiving annulus radius of three different sweep size of ceiling fan. Also suggesting user to select the ceiling fan based on their flow-field requirement. It explains the flexibility of blade design and its effect on flow field. This approach also talks about the power consumption and volumetric airflow for energy efficiency. Specifically, variation from 0.9m, 1.2m and 1.4m sweep size blades considered and compared. The flow field generated by the ceiling fans are captured by Reynolds Averaged Navier-Stokes (RANS) technique. All the tree different sweep size ceiling fans are analysed through CFD. The CFD results shows that the 1.4m sweep size blade fan gives more spread and energy efficient than other type of fans.

Analysis of the shear-driven flow in a scale model of a phase separator: Validation of a coupled CFD approach using experimental data from a physical model

The effect of shear stress at the interface between a flowing gaseous phase and a liquid-filled cavity, a scenario commonly found in flue gas/slag phase separators, is investigated in this study. This effect is frequently disregarded in computational fluid dynamics (CFD) simulations within metallurgy, primarily due to its limited influence on the motion of liquids (e.g., slag, liquid metal) when compared to other factors such as stirring by natural convection or bubbling. This study was undertaken to investigate shear-driven flow in a 1:4 scale model of a phase separator in which a flue gas stream coming from a furnace is mobilizing the flow of a slag melt. To cover a wide range of operating conditions, silicone oil with varying viscosities (20, 50, and 70 cSt) was considered for mimicking viscous slag. Additionally, different volumetric airflow rates (18, 27, and 36 m3/h) were considered to simulate the flue gas flow. Particle image velocimetry (PIV) measurements were conducted on the model. The experimental results were utilized to validate computationally efficient, coupled steady-state simulations of the system. Notably, the steady-state simulations, requiring approximately one hour of CPU time, demonstrated a computation time decrease of two magnitudes compared to conventional Volume of Fluid (VOF) modeling. A stable, laminar flow pattern of the liquid phase with surface velocities of up to approximately 30 mm/s was observed for the case with the lowest oil viscosity and the highest airflow rate, while a steady, turbulent flow was observed in the gas phase. Conversely, the lowest surface velocities, measuring around 5 mm/s, were recorded and calculated for the scenario with the highest oil viscosity and the lowest airflow rate. It was noted that velocities increased proportionally with the airflow rate but exhibited a disproportionate relationship with oil viscosity. The prediction of velocity magnitudes by the steady-state CFD model was highly accurate, with only minor discrepancies observed between the measured and calculated flow patterns. In summary, valuable insights into the often-overlooked shear stress effects at the phase boundary in gaseous-liquid flow over a cavity are provided by our study.

Experimental and numerical study of thermal and electrical potential of BIPV/T collector in the form of air-cooled photovoltaic roof tile

Among renewable energy sources, Building-Integrated Photovoltaic/Thermal (BIPV/T) systems are gaining increasing interest. To improve their economic competitiveness, technologies that increase their efficiency are searched for. The paper is devoted to evaluating the impact of various air-cooling configurations on the thermal and electrical performance of a photovoltaic roof tile. A numerical model of the own experimental system was developed in the ANSYS Fluent software for a wide range of input variables. The original approach based on the SST k-ω turbulence model, Discrete Ordinates radiation model, and the use of Solar Load module were proposed. Such a numerical model allows representation of semi-transparent layers and variable solar irradiance, which is a unique realization of real system modelling. Numerous analyses conducted indicate a higher heat recovery potential for an airflow duct with a height of 25 mm for all configurations analysed. The highest value of recovered heat flux was approximately 330 W/m2 under conditions of a volumetric air flow rate of 7.5 m3/h and solar irradiance equal to 900 W/m2. Good agreement of the results of the multivariant CFD simulations with new experimental ones was confirmed. Insight into the flow phenomena behind the achieved thermal results supplemented the knowledge. The highest electrical efficiency obtained experimentally was 5.76 % for a channel with a height of 50 mm, volumetric flow rate equal to 7.5 m3/h and solar irradiance equal to 600 W/m2. The presented methodology and the results obtained can be useful in research devoted to optimising BIPV/T air-based cooling systems, which will then be tested in-situ. Moreover, new experimental data collection can be used for the verification of numerical models.

Numerical modelling and experimental validation of dripping, jetting and whipping modes of gas dynamic virtual nozzle

PurposeThis study aims to develop an experimentally validated three-dimensional numerical model for predicting different flow patterns produced with a gas dynamic virtual nozzle (GDVN).Design/methodology/approachThe physical model is posed in the mixture formulation and copes with the unsteady, incompressible, isothermal, Newtonian, low turbulent two-phase flow. The computational fluid dynamics numerical solution is based on the half-space finite volume discretisation. The geo-reconstruct volume-of-fluid scheme tracks the interphase boundary between the gas and the liquid. To ensure numerical stability in the transition regime and adequately account for turbulent behaviour, the k-ω shear stress transport turbulence model is used. The model is validated by comparison with the experimental measurements on a vertical, downward-positioned GDVN configuration. Three different combinations of air and water volumetric flow rates have been solved numerically in the range of Reynolds numbers for airflow 1,009–2,596 and water 61–133, respectively, at Weber numbers 1.2–6.2.FindingsThe half-space symmetry allows the numerical reconstruction of the dripping, jetting and indication of the whipping mode. The kinetic energy transfer from the gas to the liquid is analysed, and locations with locally increased gas kinetic energy are observed. The calculated jet shapes reasonably well match the experimentally obtained high-speed camera videos.Practical implicationsThe model is used for the virtual studies of new GDVN nozzle designs and optimisation of their operation.Originality/valueTo the best of the authors’ knowledge, the developed model numerically reconstructs all three GDVN flow regimes for the first time.

Photo-Chemical Sucralose Degradation in an Aqueous Medium Using a Photo-Fenton System Equipped with Stainless Steel Mesh Cathodes Modified By Nanostructured TiO2- and C|TiO2-Based Films for Continuous Electro-Generation of H2O2

Artificial non-caloric sweeteners are non-bioassimilable substances that pass through the human body without biochemical changes. Sucralose, for instance, is 600 times sweeter than natural sucrose, so it is widely used in beverages and processed food products without regulation in many countries. Its environmental persistence of 337 days in sludge allows inferring that these substances can adversely affect the environment in the short or long term, thus classifying sucralose as an emergent pollutant. In this work, stainless steel (SS) mesh working electrodes were modified by TiO2- or C|TiO2-based nanoparticulate films (where C is carbon Vulcan). Both types of electrodes were employed as cathodes for the electro-generation of hydrogen peroxide (H2O2), which was the chemical precursor for photochemical producing •OH radicals able for sucralose degradation in a photo-Fenton system equipped with a 254 nm light source. Preparation of TiO2- and C|TiO2-based cathodes was performed by electrophoretic deposition method (EPD, 2 V/cm for 40 s) on AISI 304 SS mesh, followed by sintering at 450°C for 1h in the air. The EPD process was performed using aqueous colloidal suspensions containing wt./wt. ratios of C/TiO2 = 1/100 and 1/10, or TiO2 without C for comparison purposes. H2O2 electro-generation was carried out via Reaction 1 utilizing a two-electrode cell (3V-cell polarization) containing sucralose dissolved in a pH 2 aqueous sulfates buffer solution perpetually bubbled by air (volumetric flow rate of 17 mL/s) containing gaseous O2. In all the cases, a Ti grade 2.0 rod anode was immersed in the electrolyte medium with one of the following cathodes: SS* (polished, degreased, and heated at 450°C for 1h in the air as control electrode), SS||TiO2 and SS||C|TiO2 (wt./wt. ratios of C/TiO2 = 1/100 or 1/10). Furthermore, the cell was illuminated by a 254 nm lamp in order to continuous promotion of the photo-chemical Reaction 2.O2 + 2H+ + 2e- → H2O2 ...............(1)H2O2 254mn→ 2°OH...................... (2)Sucralose degradation efficiencies were registered based on the cathodes employed for continuous H2O2 electro-generation. Furthermore, the relative use time was also registered for each cathode. A comparison of these results reveals that when employed SS*, SS||TiO2, and SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/100) cathodes the sucralose degradation achieved efficiencies over 90% (i.e. 99.1, 96.8, and 91.3%, respectively). In contrast, SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/10) cathodes showed a sucralose degradation efficiency of only 88.6%. Furthermore, the SS||TiO2 and SS||C|TiO2 cathodes showed durability 3 times higher than for the SS* cathodes, and 1.8 times higher than for SS||C|TiO2 (wt./wt. ratio of C/TiO2=1/10). These observations indicated that both, SS||TiO2 and SS||C|TiO2 cathodes are strong candidates for assembling more efficient photo-Fenton systems for the degradation of sucralose and other artificial sweeteners.

Calculation of CO2 generation and required fresh air rates in a high-intensity physical athletic facility

Recently, there has been a significant growth in the number of athletic facilities associated with the progressive demand of people trying to reverse the increasingly sedentary lifestyle of current society. Cross-training facilities have become more popular in recent years among these training centers. Therefore, a detailed investigation of their indoor air quality (IAQ) is required to ensure a healthy environment for their occupants. In this study, we evaluated the IAQ of a cross-training facility in San Antonio, Texas, USA, for four days in January 2022. Each day was associated with a different air ventilation scenario involving the use of ceiling fans and an air filtration unit during the training sessions. Data from carbon dioxide (CO2) and particulate matter (PM) concentrations have been gathered for 24 h in 5-min intervals for high-intensity physical activity, such as cross-training workouts, and subsequently analyzed. CO2 concentration has been used to obtain both the infiltration rate of the building using the tracer gas decay method, and the CO2 generation rate, providing reference values as a function of the occupancy for different workout sessions. The applied methodology can be used to calculate the required volumetric fresh air flow rate to ensure a healthy environment regarding CO2 concentration in athletic facilities. In particular, the fresh air necessary rates obtained for the cross-training sessions are higher than the ones associated with sedentary activities. Finally, the deposition rate of PM from 0.3 to 10 μm has been calculated, including those potentially harmful to humans, namely PM2.5, PM5, and PM10.

Thermofluid dynamics and droplets transport inside a large university classroom: Effects of occupancy rate and volumetric airflow

The airborne droplets released by humans while speaking or coughing are the main sources of human-to-human contagion for airborne transmissible diseases. Due to the recent SARS-Cov2 pandemic, indoor transmission in classrooms and other environments is an interesting topic investigated by the scientific community. In this work, the thermofluid dynamic conditions and the droplet transport was analysed in a large University Classroom (UC), as a function of the inlet airflow and the occupancy rate. These parameters assume a relevant role in the design stage. However, their effects on droplet transport were not deeply investigated in the literature. Therefore, different conditions were analysed, such as: full occupancy, which represents the design condition where no social distancing is enforced; half occupancy, which is representative of social distancing; and empty UC, to be considered as a term of comparison. The main novelty of this work is related to the analysis of the combined effect of thermal plume and airflow in a large UC. The numerical model for the thermofluid dynamics simulation was validated in a previous work and the droplet emission model was retrieved from the literature. High volumetric airflow is not always beneficial for the reduction of the airborne transmission risk. An important aspect is related to the combined effect of the inlet airflow and the thermal plume, which cannot be ignored if the occupancy rate assumes a significant value. Moreover, the evacuation rate and the age of the droplets are relevant indicators to assess the cleaning time.

Experimental study of the discharge process of a thermal energy storage system based on granular material operated as a fluidized or confined bed

The stable generation of green electricity by Concentrated Solar Power (CSP) plants is subjected to the proper performance of Thermal Energy Storage (TES) systems, which constitute a critical subsystem of the plant. TES systems based on granular material have already been tested for industrial scale, allowing the operation at high temperature. Depending on the particle size of the granular material and the velocity of the working fluid, the bed conforming the TES system may be operated in a bubbling fluidized or a fixed bed regime. Further, beyond minimum fluidization conditions the bed can operate as fixed if the particles are mechanically confined. The performance of the discharge process of a lab-scale TES system (20.5 cm of diameter, 1 m bed height and 55 kg of silica sand as bed material) of granular material operated as a fluidized bed and as a confined bed was experimentally analyzed for various air volumetric flow rates. For the fluidized bed configuration, the bed temperature was found to be uniform along the bed height due to the high axial mixing rate caused by gas bubbles. During the discharge process of the fluidized bed TES system, the bed temperature decreased exponentially from the initial bed temperature to the temperature of the cooling fluid, with a faster temperature reduction for higher flow rates of fluid. The confined bed operation resulted in a stable temperature of the fluid at the outlet, close to the maximum temperature of the system, for around 45 min when discharging the bed with 700 Nlpm of cold air, whereas after 45 min of the discharge process, the outlet temperature of gas for the fluidized bed was roughly half the temperature obtained from the confined bed. However, the average air pressure drop during the discharge of the TES system of granular material operated as a fluidized bed is stable at around 0.16 bar, while the pressure drop of the confined bed is significantly higher, decreasing from 0.65 to 0.30 bar as the discharge process of the bed progressed.

NUMERICAL CALCULATIONS OF WATER DROP USING A FIREFIGHTING AIRCRAFT

The study involved a numerical analysis of the water dropping process by fixed-wing aircraft. This method, also known as air attack, is used for aerial firefighting, primarily in green areas such as forests and meadows. The conducted calculations allowed for the analysis of the process over time. The calculations were performed based on a SolidWorks model of the M18B Dromader aircraft. After defining the computational domain and setting the boundary conditions, the simulations were carried out using the ANSYS Fluent software. The resulting water dropping area was used to analyze the intensity of water distribution. The volumetric distribution and airflow velocity distribution were analyzed for specified time steps. The boundary layer where air no longer mixes with water during the final phase of water dropping was also determined. The obtained results provide an important contribution to further analyses aimed at optimizing the water dropping process by fixed-wing aircraft.

Experimental studies of the influence of mobile fan positioning parameters on the ability to transport the air stream into the door opening

The article aims to determine the influence of fan positioning parameters, i.e., its distance from a door opening (1–7 m) and the angle of inclination of the impeller axis in relation to the ground (0°–18°) on the amount of air flow pumped through a door opening. The experiment was carried out using a mock-up simulating a door opening, on which a measurement plane was located, without the cubic capacity (building structure) behind the door opening. The volumetric air flow stream was determined based on measuring (at 50 measuring points) the velocity of the air stream blown onto the surface of the door opening mock-up. Four commercial positive pressure ventilators, commonly used in rescue operations, with a power of 0.6–6.3 kW were tested. The tests showed that the value of the air flow stream at the most favourable setting (distance in the range of 3–5 m and the angle of the impeller axis to the ground in the range of 5°–12.2°) is included in the range of 18,304 ± 2460 m3/h to about 45,189 ± 4619 m3/h. Such settings cause the air stream to be aimed at the central area of the door opening. Imprecise mobile fan arrangement may reduce the flow rate from 41 to 76% in relation to the most favourable results.

Annular vertical cylindrical thermochemical storage system with innovative flow arrangements for improved heat dispatch towards space heating requirements

Thermochemical energy storage is a potential solution for low-temperature seasonal energy storage systems and for improving renewable solar thermal energy share in the global energy mix. Such systems can help in meeting the heating requirements in the Indian Himalayan region in an environment-friendly manner. A few studies have attempted to understand the performance of strontium bromide hexahydrate-monohydrate-based storage as a thermochemical energy storage medium. The present study evaluates the performance of the vertical cylindrical annular reactor configuration, considering innovative radial airflow configurations. A two-dimensional axisymmetric model has been developed to study the effect of the various geometrical and operating parameters. During the charging (dehydration) process, the outward flow configuration exhibits substantially higher exergy efficiency as against the inward flow counterpart, with the difference being more pronounced (∼6–8%) at lower aspect ratios (0.5–1.0). The flow work requirement is higher for the outward flow during the hydration (discharging process), resulting in better performance for the inward flow counterpart. Upon increasing the volumetric air flow rate, the pressure drop across the reactive bed is found to increase substantially, leading to lower exergy efficiencies for higher flow rates. During the hydration process, the exergy efficiency for the inward flow becomes almost constant (∼15%) for a relative humidity level exceeding 60%, whereas that for the outward flow gradually increases to reach ∼ 5% for an 80% relative humidity. The ratio of thermal energy stored to the flow work required is higher for the outward flow. The energy output to flow work ratio is about 35% higher for the inward flow for the aspect ratio of 4.

Development of an airfoil-based passive volumetric air sampling and flow control system for fixed-wing UAS

This study aims to develop a concept of a passive volumetric flow control system for gas sampling applications onboard fixed-wing UAS based on the pressure field around airfoils. The passive flow control system utilizes the aerodynamics of a UAS to create a vacuum pump effect that ensures constant gas sampling, which can be used to facilitate airborne aerosol and gas measurements. The pump effect is achieved by short-circuiting the pressure field’s minima and maxima points around an airfoil through pipes and 3D printed structures that could function both as a pump system and a gas measurement chamber. The design of this structurally integrated functionality brings many advantages for scientific applications, especially onboard small research UAS, which would dispense entirely with complex active pump systems, thus reducing weight and ensuring gas sampling at a constant volumetric flow rate independent of altitude and atmospheric variance. In favor of developing further applications, this paper outlines the development steps of the passive pump concept starting from the theory and numerical modeling of the effect to the implementation on board a fixed-wing UAS. Finally, possible improvements based on numerical models and flight measurements are discussed.

Metrological relations between the spray atomization parameters of a cutting fluid and formation of a surface topography and cutting force

Aerosol formation parameters are very important, as they are responsible for the ability of spray-forming droplets to penetrate the area to which they are applied. Research into modifying these parameters can therefore provide a solution for increasing the effectiveness of cooling and lubrication of the cutting zone during machining. This is particularly important for hard-to-cut materials such as titanium alloys, the machining of which requires the selection of effective cooling/lubricating methods to reduce tool wear or improve the machined surface quality. Previous research indicates that any modification in the air or oil flow rates – which form aerosols during cutting in minimized quantity lubrication (MQL) technique – contribute to an increase or decrease in the penetration of droplets into the cutting zone. It can consequently has a significant impact on machining results. This paper presents results on the effect of volumetric air flow rate P and cutting fluid mass flow rate E during the MQL cutting method on the machined surface topography after turning of Ti6Al4V alloy and the values of the cutting force. On the basis of conducted computational fluid dynamics (CFD) simulation studies, it was shown that the droplet size is more influenced by the change in volumetric air flow rate than cutting fluid mass flow rate and also that as the value of P increases, the droplet diameters decrease and the spray angle increases, which promotes the penetration of the cutting zone. As a result of the analysis of selected 3D surface roughness parameters, as well as contour maps, isometric views and material ratio curves, it was shown that the most favorable machined surface topography is being formed during MQL turning method with a volumetric air flow rate above 20 l/min. Whereby, with conditions of P = 30 l/min and E = 1.182 g/min, the machined surface topography is characterized by a uniform distribution of irregularity peaks and valleys, compared to the MQL turning with other tested values of aerosol formation parameters.

Analysis of ventilation in the selected lecture room – case study

The paper documents the determination of the required volumetric air flow of the ventilation unit for the purpose of ventilating the selected lecture room. The contribution briefly characterizes the legislative requirements valid in Slovakia and Poland. Particular attention was paid to the regulations of the Ministry of Health, Ministry of the Environment, Ministry of Transport and Construction of the Slovak Republic and regulations of the Ministry of Education and Sport, Ministry of Infrastructure and European standards. In the paper is documented the experimental measurement performed in the lecture room is also documented. The resulting values of the volumetric air flow required for the ventilation of the lecture room, calculated according to legislative requirements, are compared with the value calculated on the basis of the measured course of the carbon dioxide concentration.

Experimental analysis of a novel confined bed system for thermal energy storage

Thermal energy storage (TES) is an essential subsystem for the uniform operation of concentrated solar power (CSP) plants. A sensible heat storage system based on a novel confined bed of small particle size granular material was experimentally evaluated. The bed of regular silica sand was mechanically confined between a bottom and a top perforated plate gas distributor, to prevent the motion of particles even for gas velocities above the minimum fluidization velocity of the solids, operating the bed under a fixed or packed bed regime. The discharge process of the confined bed was experimentally analyzed, preheating the granular material at 300–320 °C and supplying various volumetric flow rates of cold air through the bottom distributor. During the discharge process, the temperature of the bed was segregated, obtaining a high temperature zone at the top region and a low temperature zone at the bottom region of the bed. These regions are separated by a thermocline that evolves in the upwards direction as the discharge process progresses. The temperature distribution in the bed and the total pressure drop of the TES system were monitored during the tests. For all cases, the temperature of the bed at different heights evolves as in a fixed bed, confirming the proper confinement of the granular material. The thermocline velocity depends on the volumetric flow rate of cold air, obtaining a discharge time for the temperature located at the exit of the system of around 50, 40, and 30 min for air volumetric flow rates of 700, 900, and 1100 Nlpm, respectively, using 55 kg of regular silica sand as granular material. The experimental results of the evolution and distribution of temperature in the bed were compared with an analytical model of the process for a fixed/packed bed regime of operation, resulting in a good agreement between the experimental measurements and the numerical predictions.

Influence of the Positive Pressure Ventilator Setting Distance in Front of the Doorway on the Effectiveness of Tactical Mechanical Ventilation in a Multistory Building

Proper positioning of the positive pressure ventilator is an important aspect of conducting rescue operations. The purpose of this article was to determine the effect of the parameter of the distance of setting up a mobile fan (distance from 1 to 7 m) on the efficiency of implemented ventilation in a multistory building. The volumetric airflow rate was determined by measuring the flow velocity at 120 measurement points on the surface of the window opening (which served as the measurement plane) of a four-story building. Two positive pressure ventilators were tested (one was a conventional fan and the second a turbo type). The obtained volumetric airflow values ranged from 8591 to 15,656 m3/h, depending on the type of unit and positioning distance, respectively. The analysis performed in the article showed that the general guidelines for the distance of mobile fan positioning that are present in the literature may be inaccurate and outdated.

Optimization of a Developed Multi-Cyclone Using Response Surface Methodology (RSM) to Control Fine Particulate Emission

The effects of increasing volumetric air flow rate and inlet particulate loading on overall collection efficiency of MR-deDuster; a developed multi-cyclone system was investigated using various segregated sizes of palm oil mill boiler fly ash. The operating conditions of the fabricated pilot plant scale of the unit were predicted theoretically and screened experimentally. Increasing volumetric air flow rate theoretically will increase the overall collection efficiency, yet the experimental results during screening stage demonstrated contradict finding when the increment of volumetric air flow rate caused the overall collection efficiency to be decreased for a constant particulate loading. Subsequently, the optimization work was done to determine the optimum operating conditions of the system using Response Surface Method (RSM) with Box-Behnken design. The parallel arrangement of multi-cyclone units proved the ability of the system to uniformly disseminate the gas flow with high volume of gas carrier. Nevertheless, excessive pressure drops between each unit of multi-cyclone due to high volumetric air flow rate should be avoided as such condition may lower the overall collection efficiency by allowing dust re-entrainment from the hopper to circulate between the cyclones. Through statistical analysis of variance (ANOVA), validation and verification studies, it is suggested that the developed pilot scale multi-cyclone unit would be able to meet the targeted limit of 150 mg/m3 for solid fuel burning equipment industry in Malaysia by operating with optimized volumetric air flow rate of 0.27 m3/s, and maximum inlet particulate loading rate and size of 2 g/m3 and 1000 μm respectively.

Machine learning model for predicting blast fume dilution time in underground working areas

ABSTRACT In underground mines, accurate prediction of dilution time is crucial to protect miners from toxic fumes as well as minimize production delays and ventilation costs. Previous researchers have used empirical equations, mine ventilation software, and computational fluid dynamics to calculate dilution time. These traditional methods have high computational cost and design limitations. In this research, machine learning (ML) techniques and data analytics were used to: (i) develop a ML model to predict dilution time based on five on-site blasting and auxiliary ventilation parameters and (ii) determine the order of importance of these parameters. The advantages of using the ML model over the traditional methods are its ability to consider a large number of factors, detect complex nonlinear relationships, and predict the dilution time near-instantaneously. Results show that the normalized artificial neural network has the best prediction capability with an R 2 of 0.987. Among the blasting and ventilation parameters measured, air volumetric flow rate significantly affected the dilution time, followed by duct distance from face and the amount of explosive.

The impacts of surface roughness on Indoor aerodynamics of virus-laden particles: The case of contact, deposition, and resuspension

The increasing prevalence and high morbidity of the SARS-CoV-2 virus during the COVID-19 pandemic drew widespread global attention. Surface contact is among the most common ways for the infection to spread within people, especially in buildings and the built environment. The roughness characteristics of finishing materials used in buildings vary, affecting the surface's ability to deposit and resuspend any particles that come into contact with these interfaces. Resuspension of particles indoors may increase the risk of consequent exposure through inhalation. However, little is known about surface roughness characteristics' role in airborne transmission of virus-laden particles in building indoor environments. The study examines the impact of surface roughness characteristics on the airborne transmission of the SARS-CoV-2 virus, considering indoor aerodynamic forces and their influence on particle contact with surfaces, deposition, and resuspension. The study applies Ansys Fluent CFD simulation tools to investigate the effect of volumetric flow rates and air velocity on concentration, deposition, and resuspension. The study also employs an empirical model to estimate surface roughness characteristics' impacts on particle resuspension rate. The results indicate that particle concentration and deposition rates indoors increase with increasing volumetric airflow rates. The particle resuspension rates also decreased with the increasing surface roughness of indoor surface materials. The highest resuspension rate recorded was 3.3 x 10-6, and the lowest was 1.6 x 10-6 s-1. Therefore, the outcome provides information on the implications of surface material selection and its effects on indoor air quality, health, and virus transmission. The study will offer valuable information for building engineering and design professionals in combating airborne disease transmission due to indoor surface characteristics.