Airflow Method Research Articles

10-Cell direct ammonia solid oxide fuel cell stack design development with improved efficiency and resilience to thermal shock

Hydrogen's potential as a green fuel faces a storage challenge, which has prompted recent studies to explore methods to advance solid and liquid storage, with a particular focus on utilizing ammonia. Employing hydrogen in the form of ammonia has shown considerable promise as it capitalizes on well-established and mature technologies. Nevertheless, establishing effective and resilient direct ammonia Solid Oxide Fuel Cell (SOFC) stacks demands a high degree of congruence with stack design, uniform species distribution, and temperature regulation. This research compared the conventional simple cross flow configuration with a novel approach involving two alternating fuel and air flow configurations within a 10-cell direct ammonia SOFC stack. An experimentally validated model of the direct ammonia SOFC was utilized for multi-physics modeling. The results revealed that the alternating fuel and air stacking method creates a superior ammonia decomposition profile compared to simple cross flow stacking. Moreover, the results demonstrate a lower temperature difference of 55 K within the stack. The implementation of the alternating fuel flow and air flow method enhanced the stack's efficiency by 0.74 %, primarily due to its improved thermal management capabilities within the stack. This study achieved its goal of optimizing a 10-cell direct ammonia SOFC stack by refining the design while maximizing performance and durability.

Measurement of anisotropic airflow resistance characteristics of mineral wool samples

In the field of acoustics, the airflow resistance of a porous materials like stone wool is one of the governing parameters. As a starting point, measuring the airflow resistance in the normal direction can be used for good estimations of sound-absorbing abilities when using empirical models. However, more complex models, like equivalent fluid models and Biot models, need more input parameters. The next natural step is to move into 2D and 3D interactions. An obstacle to overcome is obtaining accurate input parameters to qualify the models. The production process of stone wool introduces an inherent geometric anisotropy in the material. The aim of the study is hence to develop test and sample preparation methods that enable the measurement of the airflow resistance of stone wool sample in 3 directions by means of testing a cubic specimen. The airflow resistance was measured using a modified unidirectional static airflow apparatus. The paper presents test results obtained with the apparatus for a range of stone wool samples of varying densities. The results show noticeable differences in airflow resistance of more than 1.5 times between testing directions. This paper also, includes comparisons to results obtained using an alternating airflow method as per ISO 9053-2:2020.

One‐Step Fabrication of Nanofiber/Nanosphere Composite Membranes by Airflow/Electrostatic Method

A fabrication technology and equipment for nanofiber/nanosphere composite membranes (NNCMs) is proposed and named as the airflow/electrostatic method (AEM). AEM uses both air flow and induced electric field to stretch the jets. The AEM working mechanisms are proposed and verified. The electric field laws of AEM are obtained by finite‐element simulation and theoretical deduction. Compared with the airflow method (AM), the average fiber diameter, standard deviation of fiber diameter, and NNCMs, porosity of AEM can be reduced by 38.8%, 71.1%, and 87.3%, respectively. AEM can also overcome the shortcoming of the AM that cannot receive nanospheres. Compared with the electrostatic method (EM), AEM can not only fabricate NNCMs with randomly distributed nanofibers and nanospheres in one step, but also greatly improve the yield. The injection speeds of solution X and solution Y of AEM can be increased by 24 000% and 1920%, respectively, compared with that of EM. The diameters of AEM nanospheres and nanofibers increase with the increase of injection speed of solution X and solution Y, respectively. The distance between needle and receiver has little effect on the diameters of nanofibers and nanospheres. AEM NNCMs with excellent quality and high yield will be widely used in many fields.

Mechanical investigation of a Tandem embolization-visualization system for minimally invasive procedures

Transcatheter arterial embolization is a minimally invasive intervention process in which the blood supply to a tumor or an abnormal area of tissue is blocked. One of the most commonly used embolic agents in clinics is microsphere (MS). In order to understand the flow behavior of microspheres in arteries, it is essential to study their mechanical properties systematically. In this work, calcium-alginate MSs with varying calcium concentrations were synthesized using a coaxial airflow method. Indocyanine green (ICG) was added as a fluorescent dye. The effect of ICG concentration change on microspheres was investigated by studying morphology, imageability, rheology, and swelling behavior. Then the effect of calcium chloride concentration change on microspheres was studied by conducting rheological tests, atomic force microscopy tests, hemolysis assay, and thrombogenicity assay. Results showed that microspheres with higher ICG concentrations have longer lasting fluorescence and lower storage modulus (G′). Higher concentrations of calcium chloride led to higher G′, while the local Young's modulus obtained by AFM test was not significantly affected. The MSs with and without ICG showed good hemocompatibility and thrombogenicity.

Development of a Predictive Model for the Thermal Conductivity of Natural Fiber Insulation: A Novel Approach for Quality Control

ABSTRACT Natural fiber insulation materials can offer a sustainable alternative to mineral and petrochemical-based insulation materials when suitable raw materials and appropriate production processes are considered. Within the scope of our research, natural fibers like cotton, flax, hemp, wool, and coir, as well as regenerated cellulose fiber, were processed into insulation materials and examined concerning their thermal conductivity. We demonstrate that simple test methods for fiber fineness measurement with air-flow methods such as Airflow and Shirley can facilitate incoming inspection and process monitoring for insulation manufacturers. Based on these measurements, a simple model was developed to estimate the thermal conductivity based on the fineness measurements of the raw materials. The model developed on the natural fibers for lower densities was tested on a glass fiber insulation material to check its suitability. The slight deviations achieved between the experiment and the calculation verify the practicability of the concept.

Numerical simulation analysis and experimental verification of air flow measurement in large-diameter S-shaped pipe

Abstract The ventilation systems in nuclear power plants, hydropower plants, and other large-scale projects involve the transportation of fluids through large-scale pipelines. To achieve a more stable flow velocity distribution, the fluid needs to pass through a straight pipe section of sufficient length upon entering the pipe. Typically, this straight pipe section should be at least 15 times the inner diameter of the pipe. However, for large-diameter irregular square pipes with a diameter exceeding 1m, where the curved section is short and there are no long straight pipe sections before and after it, the flow field inside the pipe becomes complex, requiring accurate measurement of the flow rate.In this regard, a numerical simulation analysis is conducted to address this challenge. A mean velocity evaluation method based on the coefficient of variation is proposed. This method identifies multiple points within the pipe that best represent the average flow velocity, determining the insertion depth of sensors and the weight coefficients of these multiple measuring points. A calculation formula is derived, utilizing the cross-sectional average velocity as a function with the velocity values at multiple points in the flow field as independent variables. To validate the accuracy of the proposed method, flow measurement experiments are performed on a wind tunnel test bench. The calculated values obtained from the derived formula through numerical analysis are compared with the experimental results. The relative error within the full range is found to be less than 0.54%, confirming the accuracy of the formula. The research findings present a novel measurement method for airflow in large-diameter irregular square pipes and offer valuable practical insights for engineering applications.

Retting with efficient microbial consortium helps in improving jute fibre quality and profitability: a study in Eastern India

Aim: To determine the effect of application of microbial consortium for faster retting of jute (Corchorus spp.) over conventional retting without microbial consortium on jute fibre recovery and fibre quality improvement. Methodology: Large scale retting trials of jute were conducted in five important jute growing districts of West Bengal, India for four consecutive years with and without microbial consortium. After completion of jute retting, fibre was extracted manually, processed and dry fibre weight was recorded. Jute fibre samples were collected and analysed for fibre quality parameters. The fibre strength was estimated using electronic fibre bundle strength tester, fibre fineness by air flow method and root content is measured as the length of fibre up to which root is present out of the total length of the fibre and is expressed as percent length. Results: Application of microbial consortium reduced the retting duration and root content in jute fibre in all the locations irrespective of years. The jute fibre recovery increased by 9.64 to 10.97% and 9.73 to 10.63% with microbial consortium over without microbial consortium respectively in different locations and different years under study. The maximum jute fibre yield with (33.17 q ha-1) and without microbial consortium (29.89 q ha-1) was recorded in Murshidabad district. Nadia district recorded significantly higher fibre strength of 24.92 g tex-1 and lowest retting duration of 11.92 days with microbial consortium among all the locations. Interpretation: The application of microbial consortium improved the fibre recovery and fibre quality leading to the increase in net income by ₹15624 to ₹18017 ha-1 of jute farmers. Hence, the application of microbial consortium for jute retting can be used extensively by the jute farming community in jute growing states of India for faster retting of jute along with quality fibre production, higher net income and doubling farmers’ income. Key words: Corchorus spp., Fibre quality, Jute retting, Microbial consortiu

Comparison of model-driven soft measurement methods for compressor air flow in gas-steam combined cycle power units

The determination of the air flowrate at the compressor inlet is meaningful for the performance diagnosis of heavy-duty gas turbine combined cycle (GTCC) power units, whereas the compressor air flow generally cannot be directly obtained from the field data. In this paper, the procedures of three model-driven methods for soft measurement of compressor air flow were presented, including energy balance of the coupled HRSG (M1), static pressure at the compressor manifold (M2) and gas turbine joint operation line method (M3). In the case of a M701F4 GTCC power unit, the methods M1 and M3 were validated by the field and testing data; while the method M2 was calibrated and the effective area at the air manifold was decided as 12.606 m2 using M1 at the full load of gas turbine. The compressor air mass flow at overall loads was computed with the various methods. The comparative investigation to these methods shows that, the compressor inlet air flow is determined as 682.75 kg/s by M1 and 664.07 kg/s by M3, respectively, at the full load and at the ambient temperature 29.912 °C. The air flow obtained by M1 and M2 appears relatively higher than that by M3 at typical various loads of gas turbine; however, the method M3 shows a good accordance with the actual value of the air flow for turbine rotor cooling. Both M2 and M3 agree in the theoretical demonstration that compressor air flow is strongly related to the gas turbine load at certain conditions. The method M1 can be deemed as a reference for another two methods in the case of the steady operating state at full load; whereas it is not recommendable for the real-time measurement of compressor air flow, because of the large amounts of required input variables and the fluctuation in the flow meters.

Gellan Gum/Alginate Microparticles as Drug Delivery Vehicles: DOE Production Optimization and Drug Delivery.

Gellan gum is a biocompatible and easily accessible polysaccharide with excellent properties to produce microparticles as drug delivery systems. However, the production methods often fail in reproducibility, compromising the translational potential of such systems. In this work, the production of gellan gum-based microparticles was optimized using the coaxial air flow method, and an inexpensive and reproducible production method. A design of experiments was used to identify the main parameters that affect microparticle production and optimization, focusing on diameter and dispersibility. Airflow was the most significant factor for both parameters. Pump flow affected the diameter, while the gellan gum/alginate ratio affected dispersibility. Microparticles were revealed to be sensitive to pH with swelling, degradation, and encapsulation efficiency affected by pH. Using methylene blue as a model drug, higher encapsulation, and swelling indexes were obtained at pH 7.4, while a more pronounced release occurred at pH 6.5. Within PBs solutions, the microparticles endured up to two months. The microparticle release profiles were studied using well-known models, showing a Fickian-type release, but with no alteration by pH. The developed microparticles showed promising results as drug-delivery vehicles sensitive to pH.

A Visualized Method of Airflow between Adjacent Zones inside a Multizone Building Based on Pressure Difference Frequency: Airflow Mapping

The airflow movement inside a multizone building has a significant impact on pollutant transfer, thermal comfort, and indoor air quality. However, there are difficulties in visualizing the airflow movement with existing methods. This study proposes a visualization method for evaluating airflows between adjacent internal zones inside a multizone building based on the analysis of pressure difference frequency. After the distribution of absolute pressure is measured and the wind pressures on the surfaces of the building are calculated, the variation of pressure differences between each couple of adjacent zones is analyzed for three levels: greater than 0 Pa, equal to 0 Pa, and less than 0 Pa (for any given zones selected as target zones). Finally, an airflow mapping is created for each floor using the visNetwork tool based on the R language. A target building was selected for applying the proposed method. The airflow mappings were derived from a detailed analysis of the pressure difference frequency between each couple of adjacent zones, presenting the variations of airflow direction and the dominant airflow during the measurement period in a visualized form. For example, the airflow direction from 1F_Z2 to 1F_Z3 is 92.0%. The spatial similarity in the variations of the airflow directions can also be observed on certain floors. The results of this experimental study show that the airflows between multiple zones can be easily identified without a complex building zone analysis. The variation in internal airflow direction between adjacent zones can be intuitively visualized, providing insight to the airtightness levels of building components. It is also observed that the airflow rates computed based on the airflow mappings can provide more guidance for the control of HVAC systems.

Sound Absorption Properties of Charcoal Made from Wood Waste

Wood is a sustainable renewable material that is widely used in the building sector. Due to recent trends in green initiatives in European and other countries, wood waste is becoming more popular for sound absorption and insulation because of its renewability. Recycled wood material granulated charcoal is an effective acoustic treatment. In this study, we investigated the sound absorption coefficients of raw wood and granulated charcoal species: birch (Betula pendula), pine (Pinus sylvestris), and oak (Quercus robur). The impedance tube method was used to characterize the sound absorption properties of the granulated charcoal. The maximum bulk densities of the materials investigated were 567 kg/m3 for birch (B. pendula) wood and 247 kg/m3 for granulated charcoal. The airflow resistivity of wood and granulated charcoal was found using the static airflow method according to the standard. The grain size distribution of charcoal was also determined, with the highest percentage (25–29%) of the birch and pine grain distribution of charcoal species having a size of 400 µm and 30.7% of the oak a size of 1 mm. All species had the lowest grain size value, i.e., 900 µm (1–4%). The sound absorption of granulated charcoal does not depend on the carbonization temperature at 400, 500, or 600 °C. Granular charcoal of 25 mm has a better sound absorption thickness coefficient for birch at 600 °C (0.57 at 315 Hz) compared to wood of the same thickness. The effectiveness of absorption for wood and granular charcoal depends on the type of wood (birch > pine > oak), grain size, airflow resistivity, and bulk density.

Characterization of 3-D printed porous materials for use in a low cost impedance tube

With improvements in 3-D resin printing, it is now possible to design and print porous materials for testing in an acoustic impedance tube. The measured impedances of these materials can be compared to theoretical calculations. To do this, physical parameters, such as porosity and flow resistance, must be measured for the printed materials. Procedures for measuring these parameters will be discussed as well as preliminary measurements of the acoustic impedance. To measure flow resistance on the printed samples, a system based on the standard “Acoustics—Determination of airflow resistance Part 1: Static airflow method” (ISO 9053-1:2018) has been built and tested. These results will be compared to estimates of flow resistance through straight, round tubes. Porosity is measured in a simple volume comparison measurement.

Airframe design and CFD analysis of light unmanned reconnaissance aircraft

This work deals with a comparative numerical finite volume method of airflow for a 3D airframe model. The analyzed airframe model allowed 3-vector thrust directing while using the geometry of the inverted delta, which increases lift force area, allows for vertical take-off and landing, as well as full control of its flight using rotating propulsion nacelles and an airframe control system. The airframe model dimensions were 3900 x 3250 x 915 mm, enabling the installation of components of specific dimensions. CFD analysis using a four-equation transition SST model with automatic surface roughness and initial conditions: T = 288K, viscosity η= 1.7894∙ 10−5 and was carried out in the FLUENT module of ANSYS 16.0. For each simulation, 2000 iterations were performed with the intention of achieving a convergence of all residuals below 1∙10-3 using a calculation mesh consisting of 500,000 elements and 150,000 nodes. The model uses aerodynamic profile geometries: CLARK Y, NACA 6409, and NACA 2414, which are provided to obtain the optimal aerodynamic characteristics and determine the optimal range of angles of attack for the designed solution. Those angles of attack were in the range of α = 5 ÷ 10° in which the highest excellence coefficient of the carrier airfoil profile occurs. For those values of parameters optimal lift and drag forces were determined

Developing a mathematical simulation method for three-dimensional separated airflow at inlet of local exhaust devices

For local exhaust ventilation systems to be capable of removing contaminants reliably, accurate data on the velocity field around local exhaust devices is needed. The boundaries of the separation airflow at its inlet must be determined as a prerequisite for shaping leading edges of the exhaust hood. This shaping technique makes it possible to reduce local resistance, improve acoustic properties, increase contaminant capture efficiency and reduce electricity costs associated with operating ventilation systems in buildings. The goal of our study is to develop a discrete mathematical model of three-dimensional stationary separated airflow at the inlet of a rectangular exhaust duct. A novel aspect in our study is the mathematical simulation technique developed by us for 3D separated airflow at inlet of an exhaust hood. The discrete model was constructed using quadrangular vortex clouds comprising straight and curved segments, straight and curved horseshoe vortices, and closed curved vortex polygonal lines. We traced out the flow separation surface at the inlet of a sharp-edged rectangular exhaust duct and determined the axial airflow velocity using a computational procedure and a computer program designed by us. We compared our findings with the specially conducted experiment and different researchers' reports as well as values computed using complex analysis techniques for slotted exhaust hoods and our past computational data using the discrete vortex method for a square exhaust opening in non-stationary and quasi-axisymmetric settings. We found the results to be adequate. Our method can be used to determine the boundaries of vortex zones and trace out the velocity field at inlet of local exhaust hoods in a fully three-dimensional setting.

STUDY ON COMFORT EVALUATION FOR THE CENTRAL AIR-CONDITIONING SYSTEM IN RESIDENTIAL HOUSE BY CFD SIMULATION (PART 2)：THE SIMULATION METHOD OF DIFFUSED AIRFLOW AND OBLIQUE-BLOWING AIRFLOW BY MOMENTUM METHOD

The central air-conditioning system attract people’s attention because the thermal comfort can be improved by arranging the air outlets properly. Moreover, various blow out conditions may be adopted to improve the indoor thermal environment. In this research, simulation studies to improve the accuracy of CFD by Momentum method under various blow out conditions has been conducted. Firstly, the airflow distribution under each blowing condition was measured by isothermal condition. Then, the simulation method by Momentum method is proposed. In addition, airflow evaluation method of diffused airflow and oblique-blowing airflow are proposed. Finally, an efficient acceleration determination method is proposed.

Comparison between two measurement methods for airflow in circular ventilation ducts

People spend 90% of their lives indoors and only 10% outdoors. To ensure a proper ambient indoors heating, ventilation and air conditioning systems are installed. In particular, ventilation is very important in order to provide enough fresh air, but also to extract pollutants, hence to ensure a good indoor life quality. Reliable evaluation of air velocity in ventilation ducts is one of the most challenging measurements to be carried out in commissioning and operating the heating, ventilation and air conditioning systems. The present study shows a comparison of the experimental results obtained by using two different methods for measurement of the air velocity in circular ventilation ducts.

Structural optimization of disperser in polymer flooding distribution tank based on venturi pulse injection

ABSTRACT Polymer was carried by liquid in conventional polymer dispensing tank of polymer flooding in oilfield. Polymer particles often gather in the process of polymer blending, resulting in blockage of ground pipelines and formation. To reduce this phenomenon, finite element method was used. Optimization of polymer tank carrier based on venturi tube gas pulse injection. The polymer particles were carried into the liquid distribution tank by the injection method of pulse airflow to realize efficient carrying. Study on the effect of different pulse intensity and pulse waveform on cohesion. The results showed that the combined effect of strong pulse difference and pulse gap could make the airflow have strong carrying capacity for difficultly migrated polymer particles. Optimized the shortest pulse time and got the shortest time of triangle wave, sawtooth wave, square wave, and sine wave under simulated conditions. Time was 5.1 s, 6.3 s, 6.2 s, 6.2 s, respectively. The corresponding pulse frequencies were 20 times/s, 15 times/s, 10 times/s and 30 times/s, respectively. Properly increasing pulse intensity could enhance the carrying capacity of pulse airflow to polymer and reduced the carrying time of polymer. The optimal pulse parameters were triangular wave with pulse intensity of about 120 m/s and pulsed frequency of 20 times/s. Established the phenomenon and reason of indoor experiment. The viscosity of polymer solution after stirring was higher than that of liquid flow carried by gas phase pulse. This shows that the polymer system was more fully dissolved under the condition of gas phase pulse carrying. Pulsed airflow injection could effectively reduce polymer aggregation and shear action of agitator to protect polymer structure. Pulse airflow injection also plays an important role in safe operation of ground pipelines and stable seepage in porous media.

Performance study of an active-passive combined anti-frosting method for fin-tube heat exchanger

Superhydrophobic surface has demonstrated excellent anti-frosting and defrosting properties, but its effect is limited by monotonous passive application styles. In a novel active-passive combined frost suppression method for air source heat pumps, superhydrophobic modification and high-speed airflow (SMAF) are employed for frost suppression. In this work, the frosting-defrosting characteristics were experimentally studied for a fin-tube heat exchanger with the SMAF method applied under typical frosting conditions, and the results were compared with bare, hydrophilic, and superhydrophobic control groups. The influence of airflow parameters on the frost suppression effect was also revealed. Based on the experimental results, transient models for airflow parameters and frosting are established, a semi-empirical algorithm for heat exchanger performance under different anti-frosting methods is developed, and the adaptability of SMAF method to ambient temperature and humidity is revealed. The results show that the maximum net yield of the SMAF method can reach 97.9% and 18.7% respectively, compared with bare and superhydrophobic modification methods.

Monitoring and Controlling System of Chopped Tobacco Dryer Using Fuzzy Logic Method

Technological developments in post-harvest on the tobacco drying system which is a process of evaporation of water using heat energy or hot air flow aims to inhibit the growth of fungi and bacteria. The method of processing tobacco using the hot air flow method in the oven currently uses a temperature setting that is done manually and strict supervision must be carried out so that the results of the tobacco oven are not damaged. An automatic tobacco drying system can be an option so that the drying process can produce quality tobacco. By embedding the Fuzzy Logic Controller (FLC) method in the tobacco drying system, the temperature can be controlled by controlling the PWM which aims to turn the heater on and off. The tobacco drying oven system controls the oven to adjust the temperature according to the setting point of 35° and an error of 0.02% and reduces the moisture content to 25.6% remaining in the tobacco

Stability and interfacial rheology of oil-based foam with polydimethylsiloxane and natural rubber

Oil-based foam has become a research hotspot in petroleum industry, whose stability plays a key role in the application. The employment of oil-based foam prevents the damage to water-sensitive reservoir. This paper focuses on the stabilization of oil-based foam by improving the viscoelasticity of foam film and the effect study of polymer-surfactant. The Polydimethylsiloxane (PDMS) and Natural rubber (NR) are employed to stabilize oil-based foam, and the comprehensive properties of foam which created by air flow method are evaluated by FCI. Besides, the behavior of interfacial adsorption foam film is analyzed through rheological study and molecular dynamics (MD) simulation. According to the results, the oil-based foam volume increases to 150 mL and the half-life time is extended to 140 s with the combination of NR and PDMS. It is ascribed that the synergistic effect of NR and PDMS molecules. The NR molecules, which are stretched and crimped corresponding to the change of external force, begin to move toward the interface after blending with PDMS to improve the viscoelasticity of the foam film.