Airflow Direction Research Articles

Application of heat pumps in the food industry: purification plant

Furnaces and thermal chambers are created with specific guidelines in mind. These guidelines include using energy in an efficient manner, arranging products closer together to increase productivity, ensuring the direction of air flow is precise, having accurate control over temperature and humidity, making sure the equipment is reliable and convenient to use, and ensuring that any gaseous waste emissions fall within acceptable levels set by regulations. Also, a clear advantage of a heat pump is the possibility of using it at high power enterprises, where it is difficult to use water as a heating coolant. Heat pumps are also able to reduce the risk of bacterial growth, as they can maintain a safe and consistent temperature throughout the entire process. Heat pump processing is an effective and efficient method for meat products because it can achieve a high level of product uniformity with minimal product degradation.

Разработка параметрической модели определения газового состава воздушной среды (аммиак, сероводород, углекислый газ) животноводческого помещения

Indoor climate parameters influence the productivity of animals and their physiological condition. Exceeding permissible concentrations of gases leads to animal diseases, loss of productivity, and the mortality of young cattle. Therefore, it is reasonable to predict the concentration of gas composition in the livestock houses. To determine and distribute harmful gases (ammonia, hydrogen sulphide, and carbon dioxide) in the livestock house, the authors performed the 3D modeling of a fragment of the farm in the SolidWorks 2020 software package. Parametric models of gas movement under different conditions were created and optimal measurement points of gas concentration in the livestock house were determined. The simulations made it possible to determine the direction of air flows and detect accumulations and clouds of gases. The maximum concentration of carbon dioxide was detected at 0.9m (an air speed of 0 m/sec) and at 1.3m (a speed of 0.75 m/sec). The highest concentration of hydrogen sulphide was found in the area bordering the ridge space (an air speed of 0 m/s) and at the level of 2.25 m (a speed of 2 m/s). The highest concentration of ammonia was observed under the roof and in the area under the ridge (an air speed of 2 m/s). It is recommended to install hydrogen sulphide and ammonia sensors under the ridge, while carbon dioxide, hydrogen sulphide and ammonia sensors – in the stall, carbon dioxide and hydrogen sulphide sensors – near the feed table. Concentrations should be measured at heights of 500, 1500, and 3000 mm. When the concentration of emitted gas increases and other conditions are equal, the concentration of gas in the cloud increases, but the structure of the cloud changes insignificantly. Parameter interrogation sensors should be installed in enclosed ventilated boxes in the same manner as in weather stations.

Thermal Performance of Double Pass Solar Air Heater With Tubular Solar Absorber

In this investigation, the effect of replacing the conventional solar absorber with a new solar absorber on the thermal performance of a double-pass solar air heater has been studied experimentally and numerically. Three configurations have been introduced, the first configuration is a double pass solar air heater with a flat plate solar absorber (DPSAHWFP) for the aim of comparison, and the second configuration is a double pass solar air heater with a tubular absorber that includes a set of tubes which are fitted perpendicularly to the direction of airflow (DPSAHWT-1), and the third configuration is double-pass solar air heater with a tubular absorber that involves set of tubes which are fitted in parallel to the direction of airflow (DPSAHWT-2). The experiments have been carried out under indoor conditions at a constant heat flux equal to 1000 W/m2 and different air mass flow rates (0.01– 0.03 kg/s). The results revealed that the air mass flow rate has a substantial impact compared to the rise in air temperature, hence, the thermal performance of solar air heater is directly proportional to increase air mass flow rate. In addition, the experimental and numerical outcomes indicated that for all air flow rates. The (DPSAHWT-2) offers higher thermal performance as compared to other models, where the maximum effective efficiency has been obtained at 0.03 kg/s equal to 80.9 %. Moreover, (DPSAHWT-2) is more efficient than DPSAHWFP and DPSAHWT-1 by 4.2 % and 9.8 % respectively.

The generator parameters of reverse air movement in the apparatus for artificial ventilation of the lungs

The generator device of the reverse air movement for artificial ventilation of the lungs is considered. The automatic operation of the generator is ensured by the correct choice of parameters that allow realizing the effect of the air flow reverse movement at unchanged operating mode of the impeller. The change in the air flow direction occurs automatically at the required moments of reaching the limit pressure. Keywords air flow generator, reverse movement of air flow, artificial ventilation of the lungs, automatic operation

Analýza vplyvu konštrukčného riešenia batériového packu na chladenie batérií počas prevádzky

The contribution is focused on the analysis of some possible approaches to the design of air cooling of the battery pack. The battery pack is equipped with a separate fan. As part of the analysis, the influence of the location of the fan in the pack and the direction of the cooling air flow on the cooling effect and the temperature field during operation were assessed. The result of the analysis is a specific recommendation for the location of the fan in the battery pack and the design of the air flow direction.

Experimental Evaluation of Thermohydraulic Performance of Tubular Solar Air Heater

The thermohydraulic performance of a new design solar air heater (SAH) design was examined experimentally in this paper as a trial to improve the flat-plate SAH’s efficiency. A flat-plate solar air heater (FPSAH) and a jacketed tubular solar air heater (JTSAH) having similar dimensions were constructed to compare their thermal performance efficiencies. A band of Aluminum jacketed tubes were arranged side by side in parallel to the airflow direction to form the absorber of a jacketed tubular solar air heater (JTSAH). The experiments were accomplished at three mass flow rates (MFR)s: 0.011 kg/s. 0.033 kg/s, and 0.055 kg/s. Results revealed that the maximum temperature difference was obtained from JTSAH at 38°C in comparison to 32°C from the FPSAH at MFR of 0.011 kg/s. The thermal losses from the upper glass cover of the JTSAH were less than the same losses at the FPSAH due to the reduced absorber and glass temperatures of the JTSAH. The gained power was higher at the JTSAH than the FPSAH. At the JTSAH, at 0.055 kg/s MFR, the maximum average thermal efficiency obtained was 81%, and the maximum average thermos-hydraulic efficiency obtained was 75.61 %. It is noted that increasing the MFR increases the thermal efficiency, also, its optimum value rises the thermos-hydraulic efficiency to a specific optimum point. The pressure drop increases with the MFR and JTSAH compared to the FPSAH

CFD Simulation of Circulating-Airflow Distribution Inside Canopy From Novel Air-Assisted Sprayer in Orchard

HIGHLIGHTS A CFD model was developed to simulate airflow movements from circulating air-assisted sprayer. The CFD model can simulate airflow distribution inside the pear canopy with good accuracy. Simulation identifies the preferred parameters for circulating air-assisted spraying. An excessive adjustment of the airflow angle resulted in the formation of an eddy. ABSTRACT. Circulating air-assisted (CAA) spraying involves a negative pressure suction (NPS) created by a fan placed over the top of a canopy to change the airflow direction twice, i.e., first from the outside of the canopy to its inside and then from the bottom up, which can increase the airflow velocity inside the canopy. However, this new pesticide application technology has not been adequately investigated. In particular, the effects of the inlet and outlet airflow parameters of CAA spraying technology on the airflow distribution inside a canopy are yet to be determined. In this study, a computational fluid dynamics (CFD) model is developed and validated to simulate the interactions between the airflow ejected by a CAA sprayer and the canopy of a fruit tree. In the computational domain, the fruit tree is considered a porous medium. The model is validated based on three fruit trees of different sizes, leaf-area densities (LAD). The root mean square error and the mean relative square error are 1.44, 1.43, 2.22 m/s, and 24.9%, 24.7%, and 36.4%, respectively. This suggests that the CFD model can predict the interactions between the airflow field generated by a CAA sprayer and the canopy of a fruit tree. The validated CFD model is employed to analyze the airflow distribution patterns inside a canopy under different combinations of inlet and outlet airflow parameters. A reasonable combination of inlet and airflow parameters is obtained for CAA spraying technology. For example, the suitable outlet airflow velocity, top NPS, and bottom outlet angle for seven-year-old crown pear trees (average height: 2.0 m; average canopy diameter: 1.2 m; average trunk height: 0.62 m; average LAD: 2.96) selected in this study from a farm in southern China are 15 m/s, 200 Pa, and 10°, respectively. The results of this study can facilitate the parametric adjustment of CAA sprayers and enhance plant protection in orchards. Keywords: Circulating air-assisted spraying, Fruit-tree canopy, Inlet and outlet airflow parameters, Simulation.

Airflow Distribution of Hall and Classroom as Temporary Evacuation Centers: A Case Study in Melaka

During floods, the Malaysian Department of Welfare (JKM) oversees the opening and assigning of victims to evacuation centres. Public buildings such as school classrooms and community halls act as Temporary Evacuation Centers (TEC) that can last up to two weeks. The foldable tents will be provided to each family at the evacuation centres to assure that the victims have personal space. For privacy and separation, they were confined in a temporary tent with only a few fans from the building to keep their comfort. Therefore, the thermal comfort level within the temporary tent is usually affected by the airflow distribution from naturally ventilated buildings from building layout and design. In this study, two independent public buildings were hall (School A) and a classroom (School B) in Melaka, Malaysia, were investigated to simulate the airflow distribution accordingly. In-situ air sampling measures were performed using indoor air sampling techniques for 24 hours to measure the air velocity, air temperatures, and relative humidity in the building. Airflow distribution throughout the floor was used to simulate the airflow with the Computer Fluid Dynamics (CFD) model to identify the airflow direction. The average airflow rate between Schools A and B was 0.19 ms-1 and 0.27 ms-1, respectively, after the data collection. Meanwhile, the average air temperature between Schools A and B was 30.3℃ and 29.4℃, respectively. Therefore, School B's classroom layout is the best model for forecasting airflow rate, air velocity, and temperature for the evacuation center.

A modelling study on the frosting characteristics of a novel dual-fan outdoor coil in an Air Source Heat Pump unit

Uneven frosting along the airflow direction in a traditional outdoor coil in air source heat pumps (ASHPs) was inevitable due to a fixed one-way outdoor airflow direction, causing a rapid deterioration in heating performances of ASHPs. To alleviate this uneven frosting phenomenon, a novel dual-fan outdoor coil where air flow direction can be alternately reversed was proposed in a previous experimental study. To more effectively and comprehensively study the operating characteristics of ASHPs having the dual-fan outdoor coil at different fan operating modes, with different configurations and under different operating ambient conditions, a dynamic mathematical model for the experimental ASHP having the dual-fan outdoor coil was developed and experimentally validated. Then a follow-up modelling study for different operating modes of the two fans, fin pitches and operating ambient conditions was carried out using the validated model. The modelling results demonstrated that by optimizing fan operating mode, the difference in frost thickness between the windward and leeward sides of the dual-fan outdoor coil can be reduced by up to 77.3 %, the averaged output heating capacity and COP improved by up to 11.1 % and 12.7 %, respectively, and the number of switching operation of the two fans decreased by 55.6 %. Besides, the recommendations for using the dual-fan outdoor coil at different operating modes of the two fans, different fin pitches and operating ambient conditions were also made. The model can be used as a useful tool in helping achieve higher operating efficiency for ASHPs having the novel dual-fan outdoor coil.

Frost growth behavior on a vertical plate according to airflow direction at ultra-low temperatures

Frost formed on equipment operating at ultra-low temperatures (below -100 °C) affects thermal performance and leads to maintenance problems. Despite this need to study frosting behaviors at ultra-low temperatures, studies on vertical plates under forced convection are lacking. In this study, frost growth behavior at ultra-low temperatures on vertical plates was experimentally investigated with buoyancy-assisting and buoyancy-opposing flows under forced convection. Different frost growth behaviors were observed owing to the combined effects of the gravity force of the frost and the drag force exerted on the frost. Specifically, the frost layer formed in the opposing flow had a higher density and lower thickness than that formed in the buoyancy-assisting flow due to the formation of unique frost walls in the opposing flow. The frost wall not only delayed frost growth on the downstream plates but also promoted condensation phenomena in the frost wall. In addition, frosting behavior at ultra-low temperatures on the vertical plate was observed in terms of air velocity (1–3 m/s), air temperature (15–25 ℃), cooling surface temperature (-160 to -100 ℃), and absolute humidity (0.0054–0.0094 kg/kga). Additionally, correlation equations were suggested to predict ultra-low temperature frosting behaviors including average frost thickness and frost density within an error of 10%.

Effects of the Yaw Angle on Air Drag Reduction for Various Riblet Surfaces.

Biomimetic riblet surfaces, such as blade, wavy, sinusoidal, and herringbone riblet surfaces, have widespread applications for drag reduction in the energy, transportation, and biomedicine industries. The drag reduction ability of a blade riblet surface is sensitive to the yaw angle, which is the angle between the design direction of the riblet surface and the average flow direction. In practical applications, the average flow direction is often misaligned with the design direction of riblet surfaces with different morphologies and arrangements. However, previous studies have not reported on the drag reduction characteristics and regularities related to the yaw angle for surfaces with complex riblet microstructures. For the first time, we systematically investigated the aerodynamic drag reduction characteristics of blade, wavy, sinusoidal, and herringbone riblet surfaces affected by different yaw angles. A precisely adjustable yaw angle measurement method was proposed based on a closed air channel. Our results revealed the aerodynamic behavior regularities of various riblet surfaces as affected by yaw angles and Reynolds numbers. Riblet surfaces with optimal air drag reduction were obtained in yaw angles ranging from 0 to 60° and Reynolds numbers ranging from 4000 to 7000. To evaluate the effects of the yaw angle, we proposed a criterion based on the actual spanwise spacing (d+) of microstructure surfaces with the same phase in a near-wall airflow field. Finally, we established conceptual models of aerodynamic behaviors for different riblet surfaces in response to changes in the airflow direction. Our research lays a foundation for practical various riblet surface applications influenced by yaw angles to reduce air drag.

Modeling and Numerical Simulation of Axial Fan for Dry-Wet Combined Cooling System

The performance of the fan determines the thermal performance of the combined dry and wet cooling system, but its structure is complex and difficult to express with an accurate mathematical model. This paper takes the axial fan as the research object and combines its structural parameters and characteristic curves to establish an accurate single-channel numerical model of the fan. Based on this, the tangential and radial velocity changes of the airflow passing through the fan are studied, and analyze the influence of fan rotation on the direction of outlet airflow. A piecewise function fitting method with r (the distance between the calculation area and the fan axis) as the independent variable and the tangential and radial velocity at the outlet surface of the fan as dependent variables is proposed to simplify the model. The results show that in the outlet section of the fan, the tangential velocity of the fluid is 1/5 of the speed of the rotating section, and generally decreases with the increase of the distance from the outlet surface, while the tangential velocity of the fluid changes little. In addition, under the same tangent plane, the speed is distributed in a hierarchy with r, which is highly coincident with the fitted curve. The error of the calculation result is less than 2.7%. The model has high reliability. It provides a better idea for the calculation of the coupled fan of the air cooling system.

The Effect of Diameter and Position of Transverse Cylindrical Vortex Generators on Heat Transfer Improvement in a Wavy Channel

The present study investigates the effect of outer diameter (10 mm and 15 mm) and 5 positions of cylindrical vortex generators (CVGs) installed to the wavy channel in order to improve heat transfer parameters in conjunction with low-pressure drops. The wavy channels with and without CVGs are compared in terms of the local heat transfer coefficient, mean Nusselt number, Colburn factor, friction, and thermal performance for Re in the range of 857 to 8001. Furthermore, the effect of the cooling air flow direction (forward and backward) is assessed. Inserting the CVGs to the channel causes the enhancement of Nusselt numbers and Colburn factors for all CVGs positions and Re in comparison with the channels without CVGs. The maximum thermal performance factor TPFB = 0.8229 was achieved for the channel with CVGs position ‘5’ and 15 mm diameter, backward air flow, and Re = 1677. The backward air flow is more efficient compared with forward air flow since the cooling air gets into the valleys to a greater extent, and thus, better mixing of the fluid occurs. The numerical investigation, conducted with Ansys Fluent software, is compared with the experimental one acquired by holographic interferometry at good agreement of the local heat transfer coefficients. Finally, new correlating equations for the mean Nusselt number were created.

An investigation of airflow distributions with booster fan for a large opening mine through field study and CFD modeling

In this study, we conducted a field survey for the large opening mine with the survey data serving as the numerical modeling inputs to investigate the booster fan airflow distribution using a computational fluid dynamics (CFD) model. A CFD model was created with a booster fan inside the model domain, the airflow distribution patterns around the booster fan were then examined to gain insights on the booster fans impact on the air distribution in the dedicated mining section. Based on the modeling results, the booster fan is an effective ventilation control for airflow direction in large opening mine and the booster fan placement can significantly influence the effectiveness of face pollutants’ removal through airflow recirculation. The fan can boost air velocity to create the multi-pillar scale airflow recirculation to dilute the extraction heading pollutants. Furthermore, the typical continuous traverse done by many mine operators, which only covering part of the entire cross section, may be inadequate around booster fans with errors ranging from 35% to 210%. The airflow calculated at the entry adjacent to the booster fan was 25% that of the fan setting with the subsequent entries exchange diminishing by ∼65.2% per entry indicating streamlining of airflow in the booster fan entry. While the geometry of the mine will play a significant role in determining the airflow distributions this study lays the groundwork for future studies on booster fan placement optimization and effectiveness for face ventilation.

Full-Bridge Design for Error Reduction of 3-D Printed Mechanical Wind Sensor

In this article, a 3-D printed mechanical wind sensor with reduced measurement errors is demonstrated. This sensor consists of a cylindrical sensing structure arranged vertically in the center of a cross-shape cantilever. Eight strain gauges are symmetrically designed on the four beams of the cross cantilever to measure the airflow-induced cantilever deformation. With these eight strain gauges, two sets of Wheatstone full-bridge circuits can be constructed, enabling the measurement errors of the mechanical wind sensor to reduce remarkably. The experimental results indicate that, compared with the four-strain-gauge mechanical wind sensor in the previous work, the eight-strain-gauge design presented in this article can achieve a 62.4% sensitivity improvement for wind speed measurement. This increased sensitivity allows the wind sensor to realize a maximum speed measurement error of 0.53 m/s in the range of 0–30 m/s, achieving a 39.1% reduction compared with 0.87 m/s of the previous four-strain-gauge sensor. In addition, the test results also show that the proposed full-bridge sensor can define the airflow direction over the full range of 360° with a maximum error of 6°, which is 2° less than the four-strain-gauge device.

The experimental study of energy features for solar air heaters with different turbulator configurations

AbstractTo assess the thermal performance in the climate conditions of western and central Iraq, the advantages of using a solar air collector with various turbulator absorber plates are experimentally explored. Four distinct kinds of absorber plates are provided flat plate (F), triangular (T), rectangular (R), and circular (C) turbulators at different air mass flow rates. The collector's economic properties and overall thermal performance are compared to the conventional flat plate turbulator heating systems. The main findings suggest that delta turbulators improve collector economics and overall thermal performance by generating vortex and dampening the formation of the thermal boundary layer in the direction of airflow. Furthermore, when the mass flow rate increases, the thermal performance improves, and the efficiency increases for all mass flow rates, resulting in good thermal performance for the rectangular plate collector when compared to other collectors. When compared to other types of configurations, the daily average efficiency of solar air collectors for flat plate (F), triangular (T), rectangular (R), and circular (C) turbulators are 28%, 67%, 39%, and 48%, respectively, at 50° tilt angle while at 90° tilt angle they are 44%, 76%, 54%, and 63%, respectively, as ṁ = 0.0377 kg/s. The maximum daily average efficiency fitted with rectangular turbulators have about 86% at the largest ṁ = 0.1 kg/s. This study will also give a unique direction to the work trend in the western and central parts of Iraq throughout the winter months.

CT analysis of the anterior nasal airway based on the direction of nasal airflow in patients with nasal obstruction and trauma controls.

The anterior nose is the nasal segment with the highest resistance to airflow. In a hospital-based case-control study, we compared cross-sectional areas of the nasal cavities anterior to the piriform aperture determined by computed tomography (CT-CSA) in patients with nasal obstruction (cases) and unselected patients with trauma unrelated to the head and face (controls). CT-CSA could be reproducibly identified at angles of 0o, 30°, 60°, and 90° to the nasal floor approximately perpendicular to the arcuate direction of nasal airflow using bony landmarks. CT-CSA were manually segmented and compared in cases and controls. In cases, we compared CT-CSA at 30° (CT-CSA30-narrow) with the minimum cross-sectional area determined by acoustic rhinometry (AR-MCA1-narrow), each on the narrower side. CT-CSA ranged from 7 to 250 mm2 with an average of 100 mm2 per nasal side. Side differences of the nasal airways indicating asymmetry of the nasal airways were greater in 40 cases than in 44 controls (p < 0.003). Moreover, bilateral CT-CSA were significantly smaller in cases than in controls (p < 0.001). CT-CSA30-narrow did not significantly correlate with AR-MCA1-narrow (r = 0.33; p = 0.07) and on average was 58% smaller than AR-MCA1-narrow. Cross-sectional areas of the anterior nose perpendicular to the direction of nasal airflow, which is considered relevant in terms of flow physics, can be reliably measured using CT. Anterior nasal cavities in patients with nasal obstruction were more asymmetric and, as a whole, narrower than in controls, the latter of which is not corrected by routine septoplasty.

A numerical approach for preventing the dispersion of infectious disease in a meeting room

Airborne transmission of respiratory aerosols carrying infectious viruses has generated many concerns about cross-contamination risks, particularly in indoor environments. ANSYS Fluent software has been used to investigate the dispersion of the viral particles generated during a coughing event and their transport dynamics inside a safe social-distance meeting room. Computational fluid dynamics based on coupled Eulerian–Lagrangian techniques are used to explore the characteristics of the airflow field in the domain. The main objective of this study is to investigate the effects of the window opening frequency, exhaust layouts, and the location of the air conditioner systems on the dispersion of the particles. The results show that reducing the output capacity by raising the concentration of suspended particles and increasing their traveled distance caused a growth in the individuals' exposure to contaminants. Moreover, decreasing the distance between the ventilation systems installed location and the ceiling can drop the fraction of the suspended particles by over 35%, and the number of individuals who are subjected to becoming infected by viral particles drops from 6 to 2. As well, the results demonstrated when the direction of input airflow and generated particles were the same, the fraction of suspended particles of 4.125%, whereas if the inputs were shifted to the opposite direction of particle injection, the fraction of particles in fluid increased by 5.000%.

CFD Simulation Supported Development of Wind Catcher Shape Topology in a Passive Air Conduction System (PACS)

New studies and reports are published on a daily basis about the dangers of climate change and its main causes: humanity’s constantly growing population, the built environment and resource consumption. The built environment is responsible for approx. 40% of the total energy consumption, and a significant part comes from maintaining an appropriate indoor comfort environment by heating ventilation and air conditioning. Though contemporary studies have achieved a wide knowledge about natural ventilation and passive air conducting systems (PACS) and their applicability, further investigations are necessary to deepen the aerodynamic topology of air conducting building structures’ shape properties. Hence, in our current research we conducted a series of tests applying different wind catcher geometries. The methodology of this work is based on the authors’ previous work, where passive air conduction systems were compared with different airflow directions via computational fluid dynamic simulations (CFD). After finding the better performing PACS (a downdraught system), this research evaluates whether further improvements in ventilation efficiency are possible due to the aerodynamic shaping of the roof integrated inlet structures. Four different wind catcher geometries were examined to determine the most advantageous dimensional settings in the natural ventilation system’s given boundaries. After multiple series of basic and developed calculation runs, diverse shape designs of the passive air conduction inlet (PACI) were examined, including wind deflector geometries. The initial reference wind catcher’s air change rate was increased by approx. 11%. The results deliver the potential measure of improvements achievable in the aerodynamic shape design of structures under identic conditions of the same building domain. As a consequence, more sophisticated natural ventilation structural solutions will be possible in more operation cost- and performance-effective ways.

Influence of AC corona discharge on the hydrophobicity of silicone rubber surface in high-speed airflow environment

Corona discharge is one of the key factors that lead to the hydrophobicity loss of silicone rubber insulators used on the roof of high-speed trains. Based on the artificial experimental wind-tunnel platform, influences of AC corona intensity and airflow velocity on the hydrophobicity distribution of the silicone rubber surface were studied. According to the corona discharge phenomena and measured discharge current, influences of airflow velocity and voltage on the characteristics of corona discharge in a high-speed airflow environment were discussed. Results reveal that the hydrophobicity distribution on the silicone rubber surface shifts along the airflow direction in the high-speed airflow environment when the voltage is relatively high. When ionization zone develops to the needle-plate gap, the discharge path is deflected to the direction of airflow, which is responsible for the change of the hydrophobicity distribution. It is notable that the deflection distance decreases with the increase of airflow velocity. This is attributed to the fact that the electrons with variable horizontal distance from the electron to the plate electrode center are subjected to different electric field forces, resulting in different influences of high-speed airflow on them. These results are of engineering and theoretical significance for insulators used in high-speed railways.