Air Flow Rate Distribution Research Articles

Monitoring and control of air filtration systems: Digital twin based on 1D computational fluid dynamics simulation and experimental data

This study presents the development of a digital model based on one-dimensional computational fluid dynamics for the monitoring and control of filtering systems used for removing flour, dust, and other particulates from the airflow arriving from various sections of industrial production plants.Focusing on a pilot plant equipped with a cyclone bag filter, historical experimental data was integrated with the results of a one-dimensional fluid dynamics simulation model to create a digital twin capable of real-time control and regulation of industrial plants. In particular, measured pressure drop data under different clogging conditions were interpolated to generate the characteristic curves of the filter under various clogging conditions, to be implemented within the digital model of the plant. The generated model, validated through a dedicated experimental campaign, accurately predicted the airflow rate and pressure distribution across the plant. The system’s capability to adapt to changing operational conditions, such as clogging, was demonstrated through simulation, highlighting the model’s utility in maintaining the desired operation levels while minimizing the need for extensive sensor networks.The analyzed case study in the field of air filtration systems aims to fill the gap in the scientific literature related to the application of Digital Twin technology to the control of industrial manufacturing plants. The findings highlight the potential of digital twins in monitoring and control, as well as predictive maintenance, of industrial systems. The findings highlight the potential of Digital Twins in monitoring and control, as well as predictive maintenance, of industrial systems. Future research activities will explore the model’s applicability in failure and anomaly detection, to further enhance predictive maintenance of air filtering systems.

Procedure of Combustion Chamber Airflow Rate Distribution

Combustion systems are the least amenable of all gas turbine components to analyze. Among the literature overview made, it was realized that even though significant steps have been made in improving the combustor design procedure via the use of computational fluid dynamics, much of the design process still relies upon empirically derived rules. These rules include the calculation procedure of the required airflow rate by each zone of the combustion chamber to attain a suitable gas temperature, high values of combustion efficiency, low concentrations of pollutant species together with the determination of liner geometry that matches the chamber required performance goals with the constraints imposed by the engine dimensions [1,2,3, and 4]. The main target of this research work is to identify the proper procedure to distribute a predetermined airflow rate in annular type combustor and to generalize an effective calculation method that formulate and solve the problems in as much simplified and accurate manner as possible. The combustor dimensions and airflow rates in each zone is found in reference [5] and shown in Figure 1. It is designed with central vaporizing unit to deliver 516.3 KW of power with a geometrical constraint of 142 mm & 140 mm overall length and casing diameter, respectively, while the airflow rate is 0.8 kg/sec and the fuel flow rate is 0.012 kg/sec [5, 6].

Insights into air flowrate distribution and benzene removal in the heterogeneous aquifer during surfactant-enhanced air sparging

Surfactant-enhanced air sparging (SEAS) is an effective method of remediating volatile organic compounds in groundwater. In this study, the airflow migration mechanism and benzene removal in a heterogeneous aquifer during air sparging (AS) and SEAS remediation were studied using a light transmission visualisation technology. The blocking effect of the heterogeneous geological interface on airflow clearly decreased owing to the surfactant injection. At a surfactant concentration of 800 mg/L, the ΔPe value (i.e., the air entry pressure difference of the media above and below the interface) decreased from 0.3 kPa to 0.1 kPa. After surfactant injection, there was obvious downward migration owing to gravity. Compared with AS, the lateral migration of airflow at the interface and the fingered distribution of air flowrate above the interface improved considerably during SEAS, which increased the total benzene removal rates from 0.624 to 0.979. Moreover, the spatial distribution of the surfactant changed due to prolonged AS, which decreased the zone of influence area and airflow distribution range. However, the surfactant redistribution further enhanced the rectangular distribution of air flowrate, which was beneficial for continuous benzene removal in the low-permeability zone above the interface. These findings are useful for further understanding remediation mechanisms and optimising the technological parameters of SEAS technology in layered heterogeneous aquifer.

Improvement of air flowrate distribution in the nitrification reactor of the waste water treatment plant by effluent quality, energy and greenhouse gas emissions optimization via artificial neural networks models

Wastewater Treatment Plants (WWTPs) optimal operation is vital for sustainable wastewater management. Nonlinear autoregressive networks with exogenous inputs and architectures optimized by genetic algorithms (GA-NARX) were used to model energy consumption, effluent quality (EQ), and greenhouse gas (GHG) emissions. The GA-NARX were fed with 7 influent and operational variables, and were individually trained to predict 10 effluent variables and the performance indices. The mean absolute percentage error at prediction varied between 1.136 % and 21.460 %. The developed models were employed in WWTP operation optimization by unevenly distributing airflow in the aerated bioreactor. Multi-objective optimization of energy demand, EQ, and GHG emissions was used to search for the best values of the air distribution factors. Two optimization cases were investigated, the first working with EQ predicted values, while in the second case effluent concentrations were also predicted to calculate EQ and reveal the pollution loading limits violation. Selected solutions decreased the performance indices. The largest improvements were 2.01 %, 0.28 %, and 1.14 % for energy demand, EQ, and GHG emissions. The NARX models succeeded to efficiently model the WWTP main variables, predict performance indices and provide valuable support for operation optimization, leading to diminished energy consumption, improved effluent quality and reduced greenhouse gas emissions.

Ventilation indices for evaluation of airborne infection risk control performance of air distribution

Air distribution is an effective engineering measure to fight against respiratory infectious diseases like COVID-19. Ventilation indices are widely used to indicate the airborne infection risk of respiratory infectious diseases due to the practical convenience. This study investigates the relationships between the ventilation indices and airborne infection risk to suggest the proper ventilation indices for the evaluation of airborne infection risk control performance of air distribution. Besides the commonly used ventilation indices of the age of air (AoA), air change effectiveness (ACE), and contaminant removal effectiveness (CRE), this study introduces two ventilation indices, i.e., the air utilization effectiveness (AUE) and contaminant dispersion index (CDI). CFD simulations of a hospital ward and a classroom served by different air distributions, including mixing ventilation, displacement ventilation, stratum ventilation and downward ventilation, are validated to calculate the ventilation indices and airborne infection risk. A three-step correlation analysis based on Spearman's rank correlation coefficient, Pearson correlation coefficient, and goodness of fit and a min-max normalization-based error analysis are developed to qualitatively and quantitatively test the validity of ventilation indices respectively. The results recommend the integrated index of AUE and CDI to indicate the overall airborne infection risk, and CDI to indicate the local airborne infection risk respectively regardless of the effects of air distribution, supply airflow rate, infectivity intensity, room configuration and occupant distribution. This study contributes to airborne transmission control of infectious respiratory diseases with air distribution.

Effects of airflow rate distribution and nitrobenzene removal in an aquifer with a low-permeability lens during surfactant-enhanced air sparging

The application of surfactant-enhanced air sparging (SEAS) in heterogeneous aquifers has received increasing attention. In this study, a two-dimensional laboratory visualization device was used to study the migration and distribution mechanism of airflow and the nitrobenzene removal effect in an aquifer with a low-permeability lens during AS and SEAS. Experimental results showed that the surfactant significantly reduced the blocking effect of the geological interface on airflow, and the ΔPe (the air entry pressure difference between the background media and the lens) value of the geological interface decreased from 1.1 kPa to 0.3 kPa when the surfactant concentration was 800 mg/L. When the surfactant injection location was at the center of the lens and the injection volume was 1 PV (pore volume of the lens), part of the airflow entered the lens through its below interface, which clearly improved the nitrobenzene removal inside and above the lens compared with AS remediation. However, when SEAS remediation was 24 h, the surfactant redistribution caused by air sparging resulted in the airflow entering the lens to bypass the lens again, which changed the spatial distribution of airflow rate and was not conducive to the continuous removal of nitrobenzene inside the lens.

Effect of air flow rate distribution and flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration

This study investigates the effect of non-uniform distribution of the air inlet flow rate and change of air flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration. This study considers three patterns of air inlet flow rate in the transverse direction of each stack, and five patterns of air inlet flow rate in the stacking direction. The software package for simulation is reliable through an accuracy comparison, and it analyzes the current density, temperature, and thermal stress distribution of a SOFC stack with 20 layers. The results show that the progressively increasing profile of the air inlet flow rate along the x direction drops the cell thermal stress of a SOFC unit. Moreover, the non-uniform profile of air inlet flow rate in the stacking direction affects the position of the region with high thermal stress of the SOFC stack, and changing flow direction of the air obviously drops down the thermal stress without affecting the power generation of the SOFC stack.

Analyzing regularity of interpolar air motion and heat dissipation coefficient distribution of a salient pole synchronous generator considering rotary airflow

The extreme attention should be paid to cooling performance of air-cooled synchronous generators in order to ensure that the temperature rise of each part is within the allowable range. It is necessary to know losses distribution, cooling airflow rate distribution laws, heat dissipation coefficient distribution and temperature distribution characteristics. Considering the influence of rotary airflow and yoke ventilation duct structure on air motion, the physical parameters and the motion characteristics of interpolar air were analyzed in three cases. These cases were considered respectively when the rotor was in a rotating or non- rotating state and the yoke ventilation ducts were intake air, and when the rotor was in a rotating state and the yoke ventilation ducts were not intake air. Based on Multi-Reference Frame, the finite volume method was used to solve the fluid-solid coupling numerical simulation of the solving domain. Taking a 250 MW air-cooled hydro-generator as an example, the air velocity of each air cooler was measured and the inlet air velocity of the rotor support was calculated. By calculating the average temperature of the excitation winding in the steady state, the measured value and the simulation result were compared, and the correctness of the calculation method was verified.

Effects of air flowrate distribution and benzene removal in heterogeneous porous media during air sparging remediation

The decrease of remediation effect during air sparging (AS) remediation in heterogeneous porous media has attracted increasing attention. In this study, an improved light transmission visualization method was used to investigate the air accumulation, migration and flowrate distribution in benzene-contaminated heterogeneous porous media during AS. Experimental results indicated that the benzene removal rate in the porous media was mainly controlled by air flowrate distribution which could be used as a major factor to evaluate the remediation effect. Visualization of air migration showed that air accumulation occurred below the geologic heterogeneous interface when ΔPe > 0 kPa (ΔPe: the air entry pressure difference of the media above and below the interface), and the accumulation thickness and length presented exponential decay increases with increasing ΔPe and air injection rates. Air flowrate was monitored by gas flow sensors, and the flowrate distributions were found as Gaussian distribution when ΔPe ≤ 0 kPa, trapezoidal distribution when 0 <ΔPe< 0.3 kPa and fingered distribution when ΔPe ≥ 0.3 kPa. Fingered distribution of air flowrate resulted in extremely nonuniform benzene removal above the interface and reduced the overall benzene removal rate. These findings reveal the reasons for the poor performance of AS remediation in heterogeneous porous media, leading to a better understanding of the remediation mechanisms in heterogeneous aquifer.

Mechanism study of the air migration and flowrate distribution in an aquifer with lenses of different permeabilities during air sparging remediation

The poor performance of air sparging (AS) remediation in heterogeneous porous media is receiving increasing attention. However, understanding of the air migration and flowrate distribution mechanisms in heterogeneous aquifers is still lacking. In this study, for experimental purposes, a heterogeneous aquifer with lenses of different permeabilities was designed in the laboratory. The effects of the double interface between a lens and the background media on the air migration were visually observed for the first time, and four types of double interfaces and their related air flowrate distributions were identified. These were bimodal distribution (∆Pe ≤ −1.1 kPa, i.e., the air entry suction difference between the background media and the lens), fingered distribution for a low-permeability lens (−1.1 <∆Pe ≤ −0.3 kPa), Gaussian distribution (−0.3 <∆Pe < 0.4 kPa), and fingered distribution for a high-permeability lens (∆Pe ≥ 0.4 kPa). The experimental results indicated that double interface characteristics and air injection rates affected air accumulation behavior. A mathematical model was established to simulate the experimental data of the air flowrate distribution, and it could well describe the air flowrate distribution patterns in heterogeneous aquifers. These findings are significant for improving our understanding of the mechanisms of air migration and flowrate distribution in heterogeneous aquifers, leading to a better design and prediction of the AS remediation required for heterogeneous aquifer pollution.

Reducing energy costs of the wastewater treatment plant by improved scheduling of the periodic influent load

The wastewater treatment plant (WWTP) is a major actor of the water-energy nexus. This study proposes to partially store in available WWTP tank infrastructure the wastewater received during the day-time and schedule the purification of the stored wastewater at night-time. The intended operational approach aims to shift part of the WWTP electrical energy consumption from day-time into the night-time period when the energy has lower prices, also contributing to the balance of the electrical power generation system. This research presents the case study of a Romanian WWTP with Anaerobic-Anoxic-Oxic (A2O) process configuration. A proposed control strategy was implemented and tested on the dynamic calibrated WWTP model, based on the Activated Sludge Model No. 1 and the secondary settler Takács model. Simulations of the proposed scheduling program for the storing and processing time-periods of the influent wastewater, associated to the designed control strategies, demonstrate the reduction of the operational costs and energy savings, while keeping the effluent quality within the requested regulation limits and improving the plant sustainability. In the most favorable case and considering the overall WWTP performance, the operational costs are reduced by 47% and the effluent quality is improved by 25%. To achieve this performance a part of the influent wastewater is stored from 2 p.m. in the available tanks (day-period) while the beginning of the stored wastewater treatment is scheduled at 12 a.m. (night-period). Air flow rate distribution in the nitrification zone and the two water recirculation flow rates are also found by optimization.

CFD Investigation of Airflow Management in a Small Container Data Center

In this paper, the cooling performance of a small container data center is numerically investigated. It is indicated that adjusting the plenum depth and placing baffles in the plenum can improve the airflow uniformity efficiently. On the other hand, the perforated tiles with low porosity of 25% also can significantly improve the air flowrate distribution by 88.9% with the severe pumping power penalty of 2.79 times. Hence, the layout of perforated tiles with nonuniform porosities is optimized with the fixed average porosity of 50%, which can obtain almost absolutely uniform flowrate distribution in the cold aisle. In addition, the cold aisle containment (CAC) strategy is implemented, resulting in the improved rack cooling index (RCI) and supply heat index (SHI) to approach to 100% and 0%, respectively. However, the intake flowrates still suffer from nonuniformity due to the bypass effect, thus a novel criterion named flowrate uniformity index (FUI) is proposed. Besides, the drawer-type layouts with the shifting distance ( $\delta$ ) varying from 0 to 200 mm are investigated, and the case with $\delta = 150$ mm shows the best improvement in terms of the standard deviation of FUI ( $\sigma _{\mathrm {FUI}}$ ). Moreover, the $\sigma _{\mathrm {FUI}}$ of the case with a three-layer drawer-type layout can be further improved by 45.8%.

Euler-Lagrange Prediction of Diesel-Exhaust Polydisperse Particle Transport and Deposition in Lung: Anatomy and Turbulence Effects

In clinical assessments, the correlation between atmospheric air pollution and respiratory damage is highly complicated. Epidemiological studies show that atmospheric air pollution is largely responsible for the global proliferation of pulmonary disease. This is particularly significant, since most Computational Fluid Dynamics (CFD) studies to date have used monodisperse particles, which may not accurately reflect realistic inhalation patterns, since atmospheric aerosols are mostly polydisperse. The aim of this study is to investigate the anatomy and turbulent effects on polydisperse particle transport and deposition (TD) in the upper airways. The Euler-Lagrange approach is used for polydisperse particle TD prediction in both laminar and turbulent conditions. Various anatomical models are adopted to investigate the polydisperse particle TD under different flow conditions. Rossin-Rammler diameter distribution is used for the distribution of the initial particle diameter. The numerical results illustrate that airflow rate distribution at the right lung of a realistic model is higher than a non-realistic model. The CFD study also shows that turbulence effects on deposition are higher for larger diameter particles than with particles of smaller diameter. A significant amount of polydisperse particles are also shown to be deposited at the tracheal wall for CT-based model, whereas particles are mostly deposited at the carinal angle for the non-realistic model. A comprehensive, polydisperse particle TD analysis would enhance understanding of the realistic deposition pattern and decrease unwanted therapeutic aerosol deposition at the extrathoracic airways.

Analysis of Air Distribution at Molecular Sieve Vessel In RDE System Based On Fan Flow Rate Variation Using Aerosol Density Testing Facility

The Experimental Power Reactor uses the type of pebble bed fuel and helium gas as its primary coolant. Therefore, to maintain and maintain the quality of helium as a coolant in accordance with predetermined requirements helium purification system is designed. One part of the main component of this helium purification system facility that serves to absorb CO2 and CH4 is molecular sieve vessel. FASKERA is a test facility used to measure the density level of aerosols in a space in real time. To optimize the FASKERA’s performance, the characterize of its airflow rate distribution is needed. The purpose of this study is to know the airflow rate homogenous distribution in the FASKERA using fluent 6.3. The fan flow rate varied with speed 20 m/s and 25 m/s. Based on the simulation result of CFD that has been done, it can be concluded that the profile the airflow distribution within FASKERA by using a fan air flow rate of 20 m/s resulted in a more homogeneous air flow rate distribution compared to a fan air flow rate of 25 m/s, this is because the resulting drag force area is fewer and the spatial distribution area of the two airflows is evenly distributed in the chamber.

A novel flow-guide device for uniform exhaust in a central air exhaust ventilation system

Exhaust ventilation system with one central fan and multiple terminals has been widely used for the heat and contaminant removal in building environment. Conventional design without pressure balancing leads to uneven distribution of exhaust airflow rate among the multiple outlets. Existed balancing methods usually uses dampers (constant-air-volume valve or regulating valve), tapered duct, or varied inlet area. However, these methods result in higher fan energy consumption, or complicated construction and on-site commissioning. In this paper, a flow-guide device was developed for adjusting the pressure distribution of duct branches. This new device is integrated with the interflow Tee-junction and does not need any commissioning or regulating. The resistance performance of the device responding to the structural parameter was derived using the CFD simulation and experiment. The negative direct resistance featured by the device was found to effectively benefit exhaust at the outlets farther away from the central fan. The ductwork hydraulic model based on the Bernoulli's law of airflow and the fitted resistance correlations were further proposed to fulfill the parametric design. Finally, full-scale test was carried out for a central exhaust system installed with the flow-guide devices referring to a factory workshop with 30 heat and contaminant sources. Compared to the system without the devices, the total rate of the system increased by 25%. Discrepancy of exhaust rate decreased by 78% and uneven degree decreased by 82%, which well meets the engineering balancing requirement. Meanwhile, total resistance of the system reduced 23.8% owing to the negative loss the devices bring.

Effect Analysis of Floating Deck and Vents Positions on N-hexane Evaporation Loss of the Internal Floating-roof Tank

As a relatively ideal oil storage container, there is still space for further research on the mechanism of evaporation loss and the law of emission and consumption reduction of internal floating-roof rank. A small internal floating-roof tank was made to investigate the influence of vents and floating-deck positions on the distribution of airflow, wind speed, mass concentration and evaporation loss rate in the tank. The results showed that the wind speed in wall window tank is higher than that in top window tanks, but mass concentration is lower in the latter one. The higher the position of the floating-roof is, the higher the evaporation loss rate is and the better the effect of the emission reduction. It is recommended that vents should be transferred from the tank shell to the tank wall, and the influence of vents and floating decks positions should be considered in API loss formula.

Assessing Airflow Distribution in Vents of a Naturally Ventilated Test Facility Using Reference Air Velocity Measurements

Abstract. Emission measurement in naturally ventilated buildings is a complex task because wind conditions can change quickly, inducing high spatial and temporal variations in the air velocity and pollutant concentration at the vent level. Simply taking the product of differential pollutant concentration and airflow rate may generate inaccurate results because the limited number of measurement locations usually fails to correctly reflect the velocity and concentration distributions in the vents. To assess the predictability of the airflow distribution in the vents of a naturally ventilated building, detailed measurements were conducted in the vents. Linear regression was applied to velocity measurements taken in the vents and at a 10 m mast (meteomast) located 20 m away. The detailed airflow measurements were used to validate statistical models. Results showed that the velocity distribution in the ridge vent could be modeled accurately and precisely for all wind directions (R2 &amp;gt; 89%). Models for unidirectional airflows showed high predictability for the side vent (R2 &amp;gt; 92%). Models for bidirectional airflows showed good predictability for the windward side when the air flowed in the same direction as the outside wind (R2 &amp;gt; 88%) but showed less accurate results for the leeward side as well as for airflows moving in the opposite direction to the outside wind. For all models and wind directions, the most important input variable was the velocity component measured perpendicular to the vents at the meteomast. The importance of the velocity component measured parallel to the vents increased near the edges of the vent when the vent was on the windward side but did not reach the importance of the perpendicular component. The results confirmed the importance of using different models for unidirectional and bidirectional airflows to obtain accurate airflow assessments. Keywords: Airflow rate distribution, Mock-up building, Natural ventilation, Ultrasonic anemometer.

Evaluation of a Pulse Width Modulated Bypass Nozzle for the Development of a Variable Load Residential Oil Burner

Due to the need for energy conservation in buildings and the simultaneous benefit of cost savings, the development of a low firing rate load modulating residential oil burner is very desirable. One of the two main requirements of such a burner is the development of a burner nozzle that is able to maintain the particle size distribution of the fuel spray in the desirable (small) size range for efficient and stable combustion. The other being the ability to vary the air flow rate and air distribution around the fuel nozzle in the burner for optimal combustion at the current fuel firing rate. In this paper, which deals with the first requirement, we show that by using pulse width modulation in the bypass channel of a commercial off-the-shelf bypass nozzle, this objective can be met. Here we present results of spray patterns and particle size distribution for a range of fuel firing rates. The results show that a desirable fuel spray pattern can be maintained over a fuel firing rate turndown ratio (Maximum Fuel Flow Rate/Minimum Fuel Flow Rate) of 3.7. Thus here we successfully demonstrate the ability to electronically vary the fuel firing rate by more than a factor of 3 while simultaneously maintaining good atomization.

コーナーボイドを有する高層オフィスビルの自然換気性能に関する研究 （その5）新鮮外気の分配性状及び水平風力換気時と重力換気時の換気量比較

コーナーボイドを有する高層オフィスビルの自然換気性能に関する研究 （その5）新鮮外気の分配性状及び水平風力換気時と重力換気時の換気量比較

A mechanism study of airflow rate distribution within the zone of influence during air sparging remediation

In this study, an improved laboratory two-dimensional airflow visualization device was developed for the quantitative analysis of airflow distribution at different heights from the sparger (20, 30, and 40cm) within the zone of influence (ZOI). The results indicated that the measured airflow rate distribution appeared Trapezium when the height was 20cm; however, the airflow rate matched a Gaussian distribution when the heights became 30cm and 40cm. The conical shape of the ZOI was observed in the experimental processes. The experimental results verified that the airflow distribution within the ZOI conformed to turbulent jet theory. According to turbulent jet theory, the distribution of the airflow rate changes from Trapezium to Gaussian, and the jet boundary mixed layer is a linear extension in the processes of jets. Through our study, it was found that this theory could be applied to airflow distribution and predictive models for the ZOI in air sparging remediation. The shape of the ZOI should be cone-like and the boundary layer of the ZOI is a linear extension in air sparging process. All the results from this study can provide theoretical support for the design and prediction of air sparging remediation for groundwater pollution.