Air Volume Research Articles

Research on temperature distribution rule and influencing factors of integrated mechanized stope in potassium salt mine

Managing heat damage presents a significant challenge in deep mechanized stopes. Investigating and analyzing temperature distribution patterns and influential factors within the stope environment holds profound importance for enhancing thermal conditions. This study establishes a coupling model of convection and heat transfer, encompassing air flow, heat transfer, species transport and water evaporation. Additionally, a physical model is developed using the Integrated Mechanized Stope at the Laos Kaiyuan Mining potash salt mine as a representative case study. The accuracy of the numerical model is confirmed through comparison with measured data and numerical simulations. Results from numerical simulations indicate that heat dissipation from electromechanical equipment is the primary cause of stope temperature rise. In the stope stabilized airflow region, temperatures near the bottom plate are lower compared to those near the top plate, with an average temperature difference of 1.09 °C. Variation in key parameters reveals that stope temperature decreases with reduced initial airflow temperatures and surrounding rock temperatures, while it increases with diminished initial air volume. Variance analysis indicates the order of influence of key parameters on stope temperature, with initial airflow temperature exerting the greatest impact, followed by surrounding rock temperature and initial air volume. The optimal parameter scheme for controlling heat damage in the stope includes an initial airflow temperature of 22 °C, a surrounding rock temperature of 35 °C, and an initial air volume of 20 kg/s. It can reduce the average temperature of the stope's main working area to 26.21 °C. This study offers a theoretical foundation and practical reference for managing heat damage in underground mining Integrated Mechanized Stopes.

Performance analysis of range hoods with different exhaust air volumes

Performance analysis of range hoods with different exhaust air volumes

Qualitative Research on Science Lessons Based on the “Assessment Triangle”: Analyzing the Fourth-Grade Unit on the “Change in Volume of Air with Change in Temperature”

Qualitative Research on Science Lessons Based on the “Assessment Triangle”: Analyzing the Fourth-Grade Unit on the “Change in Volume of Air with Change in Temperature”

Studying the Optimal Air Volume Needed for Inflating the Cuff of an Endotrecheal Tube: A Clinical Observational Study

Abstract: An endotracheal tube (ETT) is a polyvinyl chloride (PVC) flexible plastic tube, this tube is placed into the trachea through the mouth or nose. During the course of general anaesthesia or when a patient is unable to breath by him / herself the endotracheal tube is placed for the maintenance of breathing when it is necessary to sedate the patient, and airway protection is thus lost. Endotracheal tube is used for the protection of airway from any foreign body so that air can pass into and out of the lungs by which it can maintain the airway. This tube needs a special consideration with regards to cuff inflation for creating a seal in between trachea and endotracheal tube for preventing chances of aspiration and leakage of air. Therefore, we are conducting this study to find the optimal air volume needed to inflate the cuff of ETT and minimise the complications associated with over and underinflation of cuff. The conclusion of our study shows that There was a tendency to overinflate the ETT cuff, resulting in high intracuff pressure. The estimated optimal air volume needed for inflating the ETT cuff was about 6.05 ml for men and 5.45 ml for women.

On the influence of sorbents on the static stiffness of Air Springs

Air Springs are deployed in many technical areas today. In the premium segment of the automotive industry in particular, they are being used more and more frequently. The load-independent spring rate results in a better ride comfort. Since the stiffness of the Air Spring is significantly influenced by the enclosed air volume, this usually leads to a conflict of objectives between the available installation space and the stiffness optimum. To reduce the spring stiffness while maintaining the same design space, Coackley and Elliot describe in their patent the use of adsorbents such as activated carbon in the enclosed air volume of the spring. By binding air molecules to the adsorbent, more air molecules fit into the enclosed Air Spring volume, while the size and pressure of the Air Spring remain the same.This paper describes how the so-called “virtual volume” is created by adsorption and how it can be determined by simplified measurements using a gas pycnometer. Furthermore, it is shown how these measurements are related to the static stiffness of an Air Spring, so that a prediction of the static stiffness of an Air Spring filled with sorbent, in this case activated carbon, is possible by simple pycnometric measurements.

A simulation-based investigation of the robustness of sequences of operation to zone-level faults in single-duct multi-zone variable air volume air handling unit systems

A simulation-based investigation of the robustness of sequences of operation to zone-level faults in single-duct multi-zone variable air volume air handling unit systems

Study on Variation Law of Hazardous Areas in Goaf Based on Coal Oxidation Kinetics Theory

ABSTRACT Regarding various problems on safety production in coal mines, residual coal in goaf’s spontaneous combustion is extensive, determining its hazardous areas is critical to extinguish or prevent fires in goaf. Taking production practices at the 010803-working face of Wang Wa Coal Mine as background, a combined approach involving on-site experiments, laboratory tests, and numerical simulations is adopted to investigate “three-zone” spontaneous combustion as well as the distribution patterns of temperature fields in shallowly buried coal seams. The mathematical and physical models of spontaneous combustion in goaf are constructed. Upon oxidation of coal at low temperatures, experimental data about the intensity of release of heat and the rate of consumption of oxygen inform the construction of a kinetic model for coal oxidation in goaf. Utilizing field-measured data on air leakage, a distribution model for permeability within the working face’s goaf is constructed. To study combustion “three-zone” and temperature field distribution patterns in goaf under various air supply volumes, as well as to quantitatively analyze the relationship between the width and area of oxidation zones, the area of high-temperature areas, and the distribution of high-temperature sites in the goaf, with relation to the working face’s supply volumes of air. The results show that the maximum simulated air leakage in the goaf of the working face is 148.03 m3/min, with a relative error of just 1.4% compared to the measured value. Furthermore, validation confirms that the simulated oxygen concentration variation pattern closely aligns with the measured oxygen concentration. As the airflow rate at the working face increases, the oxidation zone width at the intake side gradually grows. While on the return side, it gradually decreases, resulting in a maximum width difference of 22.6 m. The goaf area’s concentration of oxygen exhibits an “S” shape distribution pattern. The overall temperature change range within the high-temperature zone of the goaf is 4.5 K, gradually migrating toward the deeper areas. As the air supply rate rises, oxidation zone area gradually decreases, exhibiting an overall sinusoidal distribution. Concurrently, the high-temperature zone area progressively expands, conforming to a Boltzmann function distribution. When the Air supply rate is 800 m3/min to 1120 m3/min, the areas of the two are linearly correlated with the air supply volumes. Under varying air supply volumes, the position of the high-temperature point within the goaf changes in both strike and dip directions, and the relative distance with the intake air corner follows an exponential function in both strike and dip directions. Through comprehensive analysis, it is concluded that the actual air supply volume on-site should ideally range between 800 m3/min and 1120 m3/min. This range effectively prevents and controls the hazardous area of spontaneous combustion in the goaf and optimizes the ventilation scheme.

A novel approach to calculate the required volume of air for bronchial blockers in young children.

Bronchial blocker balloons inflated with small volumes of air increase balloon pressure, involving a risk of airway injury especially in young children. However, there are no established guidelines regarding the appropriate volumes of air required to provide safe bronchial occlusion. This study aimed to introduce a novel method for calculating the amount of air required for safe bronchial blocker balloon occlusion for one lung anesthesia in young children. We included 79 pediatric patients who underwent video-assisted thoracoscopic surgery at our hospital. Preoperatively, the balloon pressure and corresponding diameter of 5F bronchial blockers inflated with different volumes of air were measured. Intraoperatively, bronchial diameters measured by computerized tomographic scans were matched to the exvivo measured balloon diameters. The quality of lung isolation, incidence of balloon repositioning, and airway injury were documented. Postoperatively, airway injury was evaluated through fiberoptic bronchoscopy. Balloon pressure and balloon diameter showed linear and nonlinear correlations with volume, respectively. The median lengths of the right and left mainstem bronchi were median (interquartile range) range: 5.3 mm (4.5-6.3) 2.7-8.15 and 21.8 (19.6-23.4) 14-29, respectively. Occluding the left mainstem bronchus required <1 mL of air, with a balloon pressure of 27 cm H2O. The isolation quality was high with no case of mucosal injury or displacement. Occluding the right mainstem bronchus required a median air volume of 1.3 mL, with a median balloon pressure of 44 cm H2O. One patient had poor lung isolation due to a tracheal bronchus and another developed mild and transient airway injury. The bronchial blocker cuff should be regarded as a high-pressure balloon. We introduced a new concept for safe bronchial blocker balloon occlusion for one-lung ventilation in small children.

CO2 Concentration Assessment for Infection Monitoring and Occupancy Analysis in Tanzanian COVID-19 Isolation Centers

Monitoring of IAQ is one of the foundations of the preventative actions prompted by the worldwide recognition of COVID-19 transmission. The measurement of CO2 has emerged as one of the most popular, dependable, and easy ways to indirectly evaluate the state of indoor air renewal. Reducing the risk of respiratory diseases transmitted by aerosols is attainable through implementing and validating prevention measures made possible by CO2 control. Isolation centers are like health facilities in that they are linked to IAQ, and the presence of natural ventilation can significantly improve the circulation of fresh air, which speeds up the removal of contaminants. This is true even though healthcare facilities are among the environments with the highest rate of COVID-19 propagation. Our investigation revealed, however, that no substantial critical data on air quality in Tanzanian isolation centers is presently available. The process of metabolic CO₂ creation and accumulation within health isolation center cubicles was investigated in this study. Crucially, we suggest comparing settings under various conditions using the indicator ppm/patient. In this research, we experimentally assessed the value of changing a few HVAC system characteristics. We looked at the data to see how well the filtration system worked concerning the submicron particle concentration. Study recommendations for CO2 detectors and ways to reduce infection risk in shared isolation center cubicles are provided. We also show the correlation between particle size and CO2 concentration, the correlation between CO2 concentration derivatives and air volume presented per patient in isolation cubicles, the correlation between patient occupancy and CO2 concentration levels in isolation cubicles, and how to improve air quality by adjusting the patient’s bed position. The study also found that for exposure lengths of two to three hours, a typical hospital cubicle with fifty to one hundred people should have an average interior CO₂ value of less than 900 ppm. Carers’ length of stay in the hospital substantially impacted the permissible CO2 concentration. By establishing a connection between indoor air monitoring and healthcare goals, this study will aid in determining the feasibility of establishing regulations for interior CO2 content depending on occupancy settings, strengthening preventive efforts against COVID-19. In the post-pandemic era, it will be essential to find ways to make health facilities air cleaner so that infectious diseases cannot spread in the future.

Study on Gas-Liquid Coaxial Jet Foam Generator and Its Foaming Characteristics.

In order to solve the difficulty of the existing compressed air foam system with low FER and difficult in having both the FER and range. A new type of foam generator for CAFS was designed, an air-liquid coaxial foam generator, which produces foam with high FER (the ratio of the foam volume to the volume of the foam solution) and large output momentum. In this paper, experiments on the foam production performance of a gas-liquid coaxial jet foam generator were carried out with different parameters, such as liquid flow rate, gas flow rate, and foam output end diameter. The variation of FER, foam half-life, range, foam volume, and compressed air utilization rate with the experimental parameters were analyzed. The results show that the foaming performance of the foam generator tends to rise in the range of 8-12.4 m3/h at a fixed gas flow rate, the FER and foam half-life are negatively related to it, and the foaming performance tends to decrease in the range of 12.4-18 m3/h. The best foaming performance was achieved when the liquid volume of the foam generator was 12.4 m3/h. For the liquid volume value in different intervals, the foaming performance varies with the air supply volume. When the liquid volume is higher than 12.4 m3/h, increasing the air supply volume is beneficial to improve the foaming performance, and when the liquid volume is lower than 12.4 m3/h, increasing the air volume does not improve the foaming performance. The effect of the diameter of the foaming chamber on the foaming performance is not monotonic, and an optimum value exists. Compared with similar devices, the gas-liquid coaxial jet foam generator has strong advantages in FER and range and has better application prospects for fire control in restricted spaces.

Evaluation of microclimate in dairy farms using different model typologies in computational fluid dynamics analyses

Ventilation plays a key role in the livestock buildings since it is important to guarantee a comfortable environment and adequate indoor air quality for the animals. Naturally ventilated barns are usually characterized by high variability in the ventilation conditions. Moreover, the ventilation efficiency can be very different in different areas of a barn because of the different presence of the animals. On the other hand, appropriate ventilation is an essential requirement to ensure animal welfare and efficient and sustainable production since a proper ventilation is the most efficient way to remove undesirable air pollutants and to obtain a comfortable microclimate for the welfare of the animals. In this regard, the computational fluid dynamic (CFD) simulations represent a powerful and useful tool because they can be used to assess ventilation and microclimate conditions. In this context, the present study has the object to assess whether different CFD modelling approaches (i.e. model with animals modelled as obstacles with closed volume and model enriched with cows modelled as obstacles capable of exchanging heat with the surrounding air volume) show differences in relation to the climatic conditions inside a naturally ventilated dairy barn. The comparison of the results, set in terms of indoor air temperature and air velocity contours of the two different models, arises that if a precise definition of the microclimatic features is necessary, in order to correlate them with production parameters or assess animal welfare indexes, thermal simplification is not acceptable since can lead to completely misleading conclusions and incorrect evaluations. Then, only adopting CFD models considering the animal thermal behaviour is possible to obtain effective information both for the proper barn system management and for the creation of useful tools driving the farmers' choices.

Evaluation of microclimate in dairy farms using different model typologies in computational fluid dynamics analyses

Ventilation plays a key role in the livestock buildings since it is important to guarantee a comfortable environment and adequate indoor air quality for the animals. Naturally ventilated barns are usually characterized by high variability in the ventilation conditions. Moreover, the ventilation efficiency can be very different in different areas of a barn because of the different presence of the animals. On the other hand, appropriate ventilation is an essential requirement to ensure animal welfare and efficient and sustainable production since a proper ventilation is the most efficient way to remove undesirable air pollutants and to obtain a comfortable microclimate for the welfare of the animals. In this regard, the computational fluid dynamic (CFD) simulations represent a powerful and useful tool because they can be used to assess ventilation and microclimate conditions. In this context, the present study has the object to assess whether different CFD modelling approaches (i.e. model with animals modelled as obstacles with closed volume and model enriched with cows modelled as obstacles capable of exchanging heat with the surrounding air volume) show differences in relation to the climatic conditions inside a naturally ventilated dairy barn. The comparison of the results, set in terms of indoor air temperature and air velocity contours of the two different models, arises that if a precise definition of the microclimatic features is necessary, in order to correlate them with production parameters or assess animal welfare indexes, thermal simplification is not acceptable since can lead to completely misleading conclusions and incorrect evaluations. Then, only adopting CFD models considering the animal thermal behaviour is possible to obtain effective information both for the proper barn system management and for the creation of useful tools driving the farmers' choices.

Determination of optimal air supply form on sludge convective drying process: A CFD-DEM study

Convective thermal drying is usually used in sludge dryers, and the air supply forms significantly affect the sludge drying efficiency. In this work, the drying process of multi-layered sludge is numerically simulated using a coupled computational fluid dynamics-discrete element method (CFD-DEM) approach. Better than our previous work, the current CFD-DEM model further considers the dynamic process of humidity within the flow field. Firstly, the CFD-DEM model is validated based on the mechanistic experimental data. Then, extensive numerical simulations are carried out to investigate the two-layered sludge drying process in the dryer, and the effects of two conventional air supply forms (Top-to-Bottom and Bottom-to-Top) as well as a novel air supply form (Side-assist) on the two-phase flow system are discussed. The simulation results provide in detail the dynamic processes of momentum, heat and mass (moisture) in the convective drying system under different working conditions. Following recommendations are presented to facilitate the operation of the dryer: Bottom-to-Top is better for sludge drying and tends to utilize less heat from the heat source compared to the Top-to-Bottom. The drying efficiency can be further improved by supplying the Side-assist with an optimal flow ratio of side-wind to bottom-wind. Numerical results show that the optimal flow ratio is related to the total air volume, the deflection angle and the side-wind temperature. The present study reveals in depth the impact mechanism of the air supply form on the convective thermal drying process of sludge, which contributes to the design and optimization of high-efficiency dryers.

A novel dynamic predictive control model for variable air volume air conditioning systems using deep learning

Model-based predictive control has proven effective for managing indoor temperature and humidity in variable air volume (VAV) air conditioning systems. However, delays in temperature and humidity adjustments in response to changes in internal and external environmental conditions can impede high-performance operation. This study introduces a dynamic predictive control model for the multi-zone indoor temperature and humidity of VAV systems, designed to predict and control these parameters in real-time. Utilizing the RC network two-node wall structure method and backward finite difference scheme, a multi-zone building model is developed. Coupled with a deep fuzzy cognitive map (DFCM) for temperature and humidity prediction, and controlled by a PID controller, the model dynamically regulates the opening degrees of terminal air dampers and chilled water valves. Implemented on a networked control platform in a large commercial building, the model consistently maintained indoor temperature and humidity within ±0.5°C and ±0.1 g/(kg dry air) of the target values under varying conditions, demonstrating substantial improvements in stability and operational efficiency. The research enhances the predictability and control of HVAC systems through advanced algorithmic integration, improving real-time indoor climate management in complex building environments. This method offers a practical improvement in HVAC control technologies, which could be beneficial for applications in commercial building management systems, providing a useful tool for supporting energy efficiency and sustainability in modern infrastructures.

Advanced modeling of segmented Halbach cylinder for ironless brushless permanent-magnet two-phase motor

Compared with conventional permanent magnet (PM) cylinders, Halbach magnet cylinders have the advantage of strengthening the magnetic field on one side and canceling the field on the other side of the magnet structure. Outer-rotor radial-flux brushless ironless PM machines using a Halbach cylinder, therefore, can have a higher torque density compared with the ironless PM machines using a conventional magnet cylinder with the same magnet and coil volume and same air gap. For outer-rotor Halbach cylinder motors, existing designs usually take advantage of the fundamental harmonics of the magnetic field to obtain a linear toque model and to avoid the torque ripples from the higher-order field harmonics. To achieve this, the Lorentz coils must be placed where the fundamental harmonics of the field is dominant and the higher order harmonics can be negligible. With this, the coils should be sufficiently far from the magnet cylinder’s surface. However, how far the coils should be (from the magnet) is not clarified from the reported designs. To provide guidance on where to optimally place the Lorentz coils and to make the best use of the Halbach cylinders, there is a critical need for a simple but comprehensive analysis to find out all the field harmonics everywhere for both the ideal and segmented Halbach cylinders. This work is to provide that analysis.

Effect of air volume flow rates on pyrolysis temperatures and flue gas compositions to control smoldering smoke generation

Effect of air volume flow rates on pyrolysis temperatures and flue gas compositions to control smoldering smoke generation

Analyzing Vital Capacity in Short-Term COVID-19 Survivors between 20 to 40 years and over 40 years Population: Understanding Respiratory Health in New Normal situation

COVID-19 global coronavirus is a pandemic caused by coronavirus 2 (SARS-CoV-2). Coronavirus effect on multiple organ dysfunction but pulmonary function is most affected area of a patients. Pulmonary function or vital capacity have significance in the treatment of COVID affected patients. Vital capacity is defined as the maximal volume of air that can be exhaled from the lungs following maximal inspiration. Present study aim is to compare vital capacity between COVID-19 survivors and non-COVID populations. A total of eight hundred fifty-nine (859) subjects of different ages have been selected for the present study. The present study data were collected by the Multi-Functional Spirometer HI-801 for vital capacity, and the digital weighing scale was used for the measurement of body weight. The collected data was analyzed using descriptive statistics, the mean and the standard deviation (SD). An inferential statistically paired and independent t-test was applied to check the level of significance. The significance level was set at p&lt;0.05. The results of this study, male COVID survivors between the ages of 20 to 40 have better vital capacity recovery than male COVID survivors over the age of 40, while female COVID survivors between the ages of 20 to 40 outperform female COVID survivors over the age of 40. Female COVID-19 survivors generally regain essential capabilities far more quickly than male survivors. We conclude that female COVID survivors recover vital capacity much faster than male COVID survivors.

In silico analysis of airflow in a single path configuration of the pulmonary tree

In silico analysis of airflow in a single path configuration of the pulmonary tree

COMPARATIVE ANALYSIS OF ENERGY EFFICIENCY OF THERMAL OPERATION OF ROTARY KILNS WITH DIFFERENT HEATING SYSTEMS

Analysis of the design features of known heating systems for large rotary kilns and modern methods of influencing the formation of the flame and the distribution of the temperature profile is presented. It has been established that most of the known methods of forming the flame and temperature profile of the working space of rotary kilns are based on methods of influencing air flows, in particular secondary air, the share of which in the total volume of combustion air is 70–100 %. On the basis of previous studies and observations, it is proposed to form a flame using additional sideways gas jets from the burner. Examples of modernization of heating systems of existing industrial rotary kilns for firing various materials, including ferronickel ore, fireclay, and lime, are presented. After installing burners with controlled flame parameters and changing the design of the combustion air supply system in the working space of the kilns, an optimal temperature distribution along their length was obtained. It was determined that the required temperature at about half the length of the kilns is almost constant, without significant fluctuations, differing at the beginning and end of the firing zone by 30–70 °C. The decrease in the temperature of the exhaust gases from the kilns after the modernization of the heating systems indicates an intensification of heat exchange in the workspace, which leads to a decrease in specific fuel consumption by 7–15 %, as well as an improvement in the quality of the final material. A comparative analysis of the thermal efficiency of operating rotary kilns depending on the design features of the heating system is presented. Bibl. 24, Fig. 4.

Numerical Simulation of Tunnel Ventilation Considering the Air Leakage Mechanism of a Ventilation Duct

Ventilation problems are critical in tunnel engineering, and the loss of air volume in ventilation ducts is generally estimated using empirical methods. The air volume calculation makes it difficult to meet the accuracy requirements, resulting in resource waste or insufficient air supply. In this study, the forced ventilation system of the tunnel under construction was investigated based on the computational fluid dynamics method. The mechanism of air leakage on airflow distribution and pollutant transport in the tunnel is determined. Air leakage reduces the distribution peak of pollutants and effectively accelerates the emission of harmful gases. However, this effect decreases with distance from the air duct inlet. Through the calculation results of nearly one hundred models, it is found that the air leakage of the duct can be fitted by logarithmic function and verified by empirical equation. The matching degree between the fitting function of the model and the empirical equation depends on the length of the tunnel. On this basis, the calculation formula of effective air volume near the working face is derived. This study can be applied to the ventilation engineering of the tunnel under construction and provide a theoretical basis for the calculation of the effective air supply.