Forced Air Flow Research Articles

Fruit detection, yield prediction and canopy geometric characterization using LiDAR with forced air flow

Yield monitoring and geometric characterization of crops provide information about orchard variability and vigor, enabling the farmer to make faster and better decisions in tasks such as irrigation, fertilization, pruning, among others. When using LiDAR technology for fruit detection, fruit occlusions are likely to occur leading to an underestimation of the yield. This work is focused on reducing the fruit occlusions for LiDAR-based approaches, tackling the problem from two different approaches: applying forced air flow by means of an air-assisted sprayer, and using multi-view sensing. These approaches are evaluated in fruit detection, yield prediction and geometric crop characterization. Experimental tests were carried out in a commercial Fuji apple (Malus domestica Borkh. cv. Fuji) orchard. The system was able to detect and localize more than 80% of the visible fruits, predict the yield with a root mean square error lower than 6% and characterize canopy height, width, cross-section area and leaf area. The forced air flow and multi-view approaches helped to reduce the number of fruit occlusions, locating 6.7% and 6.5% more fruits, respectively. Therefore, the proposed system can potentially monitor the yield and characterize the geometry in apple trees. Additionally, combining trials with and without forced air flow and multi-view sensing presented significant advantages for fruit detection as they helped to reduce the number of fruit occlusions.

Computational fluid dynamics modeling and laboratory analysis of aerosol particles' capture on thin swirling water film in a Vortecone

This study was conducted to look at a new use case for the Vortecone scrubber. A Vortecone is an inertial separator that utilizes the momentum of dust particles to promote their capture. The turbulent airflow forces the water supplied at the periphery to deform continuously, resulting in a rapidly swirling film on the Vortecone surface. The heavier dust particles are differentially shed from the bulk airflow towards the vortex chamber surface where they are captured by the running water film. The Vortecone surface serves as the filter element. The authors use computational fluid dynamics to model the multiphase flow and particle transportation inside the Vortecone. Laboratory experiments using coal dust show the Vortecone to capture about 73% and 97% of particles exceeding 2.9μm and 5.9 μm at 0.28 m3/s. The cleaning improves to 89% and 99% at the airflow of 0.38 m3/s .

Effect of evaporative cooling and altitude on dairy cows milk efficiency in lowlands.

The objective of this current work was to determinate the effect of high temperatures on milk production of dairy cows in southern Slovakia in the year 2015. The hypotheses that milk production is influenced by the altitude and cooling were tested. Production data included 227,500 test-day records belonging to 34 Holstein breed herds situated in lowlands, 115 to 150 m above sea level (ASL) and kept in free-stall housing. Dairy farms were classified into groups based on cooling system. The first group of cows (19 herds) was cooled evaporative (foggers) and forced ventilation, and the second group (15 herds) was using cooled only forced ventilation (automatically controlled fans in housing and feeding areas). During the period from May to September, 36 summer and 22 tropical days were recorded, 37 days had a mean thermal humidity index value above 72.0, and on 34 days we recorded mean values above 78.0. The highest milk yields were recorded at the altitude 1 (115 m ASL) (9219.0 kg year-1; 10327.0 kg year-1) and the lowest at the altitude 2 (126 m ASL) (7598.7 kg year-1; 8470.21 kg year-1) (P < 0.001). Dairy cows cooled evaporative milked significantly more milk than cows cooled only with forced air flow (9650.4 kg vs. 8528.0 kg; P < 0.001). Fat and protein production differed also significantly (364.0 kg vs. 329.5 kg, P < 0.001; 312.2 kg vs. 279.7 kg, P < 0.001). It can be concluded that not only heat stress but also location farm above sea level can affect milk production. Evaporative cooling associated with increased air velocity is the appropriate protection against high temperatures.

CFD study to improve PV cell performance by forced air: Modern design

A theoretical study was conducted on the performance of photovoltaic cells by forced airflow on the cell base. The study was conducted using numerical simulation software (ANSYS- cfx) to select the best model for its manufacture. The simulation results showed that the air guides model is the best, directing the largest amount of air to the base of the cell and the lowest cost and available in local markets. Air guides shall be installed inside an aluminum channel fixed to the bottom of the cell base and the channel dimensions shall be selected according to the dimensions of the photovoltaic cell to be cooled. A numerical study determine the best number and best location of the air guides inside the duct channel and the tilt angle of air guides and showed that the optimum number of pneumatic guides is (18) in a position (70 mm) from the base of the channel and at a 45-mile angle with the horizon.

Electrically enhanced drying of white champignons

Electrohydrodynamic (EHD) drying is novel nonthermal technology exploiting high-voltage corona discharge for dehydration of heat-sensitive biomaterials. In this study, we investigated the effects of voltage, electrode geometry, air flow, humidity, and material thickness on drying rate of sliced white champignons. In most cases, drying rate of mushrooms was proportional to moisture content, which corresponds to diffusion-limited drying. Decrease of air relative humidity from 70 to 30% or introducing forced air flow 1.0 m/s significantly improved efficiency of EHD drying. Increase of emitters’ density or thickness of mushroom slices negatively influenced drying rate. Effect of EHD on color was insignificant in contrast to forced air drying, which provoked significant browning. Energy, used in EHD drying, was negligibly small as compared to thermal drying. These results have been taken into consideration for up-scaling of the EHD drying.

Lateral Flame Spread over PMMA Under Forced Air Flow

In wildland and other flame spread scenarios a spreading fire front often forms an elliptical shape, incorporating both forward and lateral spread. While lateral flame spread is much slower than forward rates of spread, it still contributes to the growth of the overall fire front. In this work, a small-scale experiment is performed to investigate the mechanisms causing this lateral spread in a simple, small-scale configuration. PMMA strips with thicknesses ranging from 1 mm to 3.1 mm and widths of 5 cm and 10 cm were ignited under forced flow in a laminar wind tunnel. Unlike traditional concurrent or opposed flame spread experiments, flames were allowed to progress from one side of the sample to the other, perpendicular to the wind direction. An infrared camera was used to track the progression of the pyrolysis front by estimating the surface temperature of the PMMA. The flame spread rate, depth of the burning region, thermal diffusion length, and radiant heat flux were determined and analyzed. Based on a theory of heat and mass transfer for a laminar diffusion flame, a thermal heat transfer model was developed for the preheating region to predict the lateral flame spread rate. Results show that the thermal diffusion length decreases with wind velocity, ranging from 4.5 mm to 3 mm. Convection dominates the flame-spread rate, accounting for more than 80% of the total heat flux. The theoretical flame spread rate agrees well with experimental data from all but the thinnest samples tested, overpredicting the lateral flame spread rate for 1 mm thick samples. The resulting model for lateral flame spread under concurrent flow works for forced-flow dominated flame spread over thermally-thin fuels and helps provide physical insight into the problem, aiding in future development of two-dimensional, elliptical fire spread models.

Computational Fluid Dynamic Design and Experimental Study of a Temperature Sensor Array Used in Climate Reference Station

Accurate air temperature measurements are demanded for climate change research. However, air temperature sensors installed in a screen or a radiation shield have traditionally resisted observation accuracy due to a number of factors, particularly solar radiation. Here we present a novel temperature sensor array to improve the air temperature observation accuracy. To obtain an optimum design of the sensor array, we perform a series of analyses of the sensor array with various structures based on a computational fluid dynamics (CFD) method. Then the CFD method is applied to obtain quantitative radiation errors of the optimum temperature sensor array. For further improving the measurement accuracy of the sensor array, an artificial neural network model is developed to learn the relationship between the radiation error and environment variables. To assess the extent to which the actual performance adheres to the theoretical CFD model and the neural network model, air temperature observation experiments are conducted. An aspirated temperature measurement platform with a forced airflow rate up to 20 m s−1 served as an air temperature reference. The average radiation errors of a temperature sensor equipped with a naturally ventilated radiation shield and a temperature sensor installed in a screen are 0.42° and 0.23°C, respectively. By contrast, the mean radiation error of the temperature sensor array is approximately 0.03°C. The mean absolute error (MAE) between the radiation errors provided by the experiments and the radiation errors given by the neural network model is 0.007°C, and the root-mean-square error (RMSE) is 0.009°C.

Real-life budesonide and formoterol dose emission from the medium and high strength fixed dosed combinations in a Spiromax® dry powder inhaler using inhalation profiles from patients with chronic obstructive pulmonary disease

Dry powder inhalers (DPIs) are passive devices used to administer inhaled medication for the management of asthma and chronic obstructive pulmonary disease (COPD). DPIs require patients to generate a sufficient internal turbulent airflow force during each inhalation to deaggregate the powdered drug formulation into an emitted dose containing particles with the greatest likelihood of lung deposition. This internal force is generated by the interaction between the user's inhalation flow and the resistance of the DPI. Traditional compendial in vitro methods of measuring dose emission use a vacuum pump to simulate inhalation. We have adapted this in vitro method by replacing the square wave inhalation profile generated by a vacuum pump with the inhalation profiles of patients using an empty DPI. This method enables accurate assessment of the actual dose they would have inhaled. In the present study, real-life inhalation profiles were selected from 15 patients with COPD who inhaled through an empty placebo Spiromax® DPI. Ex vivo dose emissions were measured for the medium (emitted dose of 160 μg/4.5 μg) and high-strength (320 μg/9 μg) budesonide/formoterol formulations from the Spiromax DPI. These profiles were used to investigate the effect of the primary inhalation parameter—peak inhalation flow (PIF). Some profiles were modified to isolate other inhalation parameters (namely, inhaled volume [Vin] and acceleration rate of the inhalation maneuver [ACIM]). Both the medium-strength and high-strength DuoResp Spiromax displayed flow-dependent dose emission. When the PIF of a patient's inhalation maneuver increased from 26.8 L/min to 69.7 L/min, there was a significant (p < 0.05) effect on the dose-emission characteristics of the medium-strength and high-strength DuoResp Spiromax. At each PIF, an increase in Vin from approximately 500 mL to 2000 mL had no effect on the dose-emission characteristics of either strength. However, at each Vin there was a significant (p < 0.05) effect on the dose-emission characteristics as PIF increased. The effect of ACIM on the dose-emission characteristics was small. The ex vivo methodology used in this study provides a practical approach to identify the actual dose a patient might inhale during routine real-life use of the DuoResp Spiromax.

Influence of ambient pressure on critical ventilation velocity and backlayering distance of thermal driven smoke in tunnels with longitudinal ventilation

Thermal driven smoke backlayering in tunnels with longitudinal ventilation is a huge threat to the trapped people during fires. To explore the influence of ambient pressure on smoke backlayering distance and critical ventilation velocity of thermal driven smoke flow, fire simulations with varying ambient pressures and heat release rates (HRRs) were carried out in a full scale tunnel with longitudinal ventilation. The results suggest that for a certain HRR and longitudinal ventilation velocity, the smoke backlayering distance increases with the decrease of ambient pressure due to the weaker inhibiting effect of longitudinal airflow, which is characterized by the decrease of the ratio of the horizontal inertial force of longitudinal airflow to thermal buoyancy of the smoke backlayering. Moreover, a parallel analysis for critical ventilation velocity was also made, and it has been found that the critical ventilation velocity increases with the decrease of ambient pressure for a certain HRR. Based on the dimensional analysis, a correlation of dimensionless critical ventilation velocity is proposed and is compared with previous correlations at normal pressure. Finally, the credibility of correlation are validated by comparing with experimental results from large and full scale tunnel fire tests.

Disassembly of waste printed circuit boards using air heating and centrifugal force

Waste electrical and electronic equipment is a significant source of material that can contribute to reduce environmental impacts associated to extraction and discard stages; therefore, it is necessary to develop efficient recycling processes for components such as Printed Circuit Boards (PCBs). Current methods for PCB recycling may be optimized by previous disassembly of such components. In the work reported here, an especially designed and manufactured centrifuge was employed to disassemble PCBs from power supplies (PS-PCBs) and memory chips (ME-PCBs) of personal computers (PCs), through combination of hot air flow and centrifugal force. The results showed that the device was capable of separating tin solder, electronic components (EC) and PCB substrate, as long as hazardous components and plastic parts are previously removed. A scanning electron microscope (SEM) with combined energy dispersive X-ray (EDX) analyzer showed that the recovered solder had under 3%wt of contamination; therefore, it can be employed in the production of new soldering material, replacing the more commonly used solder dross. EC recovery rates were up to 94%wt for PS-PCBs and 32%wt for ME-PCBs, and once components such as inductors were not visibly damaged in the process, possibilities of reusing recovered components may be further investigated.

Conditioning of Tobacco and Tobacco Products: The Effect of Forced Air Flow

Summary Conditioning is a very important procedure for tobacco and tobacco products before their corresponding chemical and physical analysis. For cigarettes, forced air flow is generally required during the conditioning procedure. A special wind tunnel was designed to investigate how the forced air flow affects the conditioning of cigarettes in a constant climate laboratory. Two types of cigarettes with blended (including flue-cured and burley tobacco strands) and pure flue-cured tobacco strands were selected as test samples. It was found that the conditioning time to achieve the equilibrium could be shortened from 23 h without forced air flow to 7 h with a forced air flow rate of 2m/s. This is mainly due to the exchange of water molecules between cigarette samples and atmosphere being accelerated by applying the forced air flow. It was concluded that a 48 h conditioning period using the described forced air flow rate setup was unnecessary to attain the equilibrium for cigarettes. [Beitr. Tabakforsch. Int. 28 (2019) 224–229]

Mathematical modeling of heat storage unit for air heating of the building

In this paper, the thermal performance of the heat storage unit made of repeatable modules was carried out. The heat accumulator that is used in solar installations may be a separate unit, or it may be a building wall insulated on the inner and outer surfaces. It is a heat storage unit with dynamic discharge using forced air flow through the channels. The transient temperature field in the walls of the channels was modeled using three different methods: finite volume method (FVM), control volume based finite element method (CVFEM), and finite element method (FEM). The CVFEM was chosen for the construction of a full model of the heat storage unit due to the ease of modeling a solid filling of a heat storage unit with a complex shape. The numerical model of the heat storage unit with the air flow through channels was developed. The CFD simulation was also carried out. In the mathematical model of the heat accumulator, it was taken into account that air flow can be laminar, transitional or turbulent. The finite volume method with integral averaging of air temperature over the finite volume length was developed so that accurate air temperature distribution can be determined even with a small number of finite volumes.

Numerical analysis of loss of vacuum accident (LOVA) and preliminary discussion about dust resuspension for CFETR

Loss of vacuum accident (LOVA) is the air ingress into the vacuum vessel (VV) due to the failure of components. The high speed air jet flow induced by the pressure difference between the ambient condition and the in-vessel condition may cause the dust migration, re-suspension bring risk to the integrity of components and radioactive release. The present work deals with the computational fluid dynamics (CFD) modeling of airflow characteristics in different scenarios during the LOVA for CFETR. Then, forces applied on the deposited particles are investigated, based on which the preliminary discussion are carried out to analyze the possibility of dust resuspension in various LOVA scenarios. The results show that the break location, break size and the operational status during the LOVA have significant influence on the key parameters related to airflow forces such as the friction velocity. Furthermore, the airflow force gradually plays the dominate role as the particle diameter increases. It preliminarily demonstrates the possibility of dust resuspension as the particle diameter changing. The results can provide references to study the dust re-suspension and implement accident mitigation measures.

Measurement of dust-borne MRSA in pig farms using different approaches.

To obtain knowledge about (i) how to sample airborne methicillin-resistant Staphylococcus aureus (MRSA) and dust in the pig farm environment including effects of sampler on (a) measured exposure, (b) MRSA survival and (c) spatial and temporal variation in exposure, and (ii) the association between exposure to MRSA, dust and optical density OD. Airborne dust was sampled on five pig farms using five active and one passive samplers. Staphylococcus aureus and MRSA (as a subset of S. aureus) were quantified using selective agar media and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The Andersen sampler, electrostatic dust collectors (EDC), and Gesamtstaubprobenahme (GSP) and Institute of Occupational Medicine samplers with polycarbonate or Teflon filters were applicable for sampling airborne MRSA. The half-life of MRSA was not reduced by active sampling. A significant correlation was found between dust and S. aureus exposure within, but not between, farm section and farms. A significant spatial and temporal variation in dust and MRSA exposure was found within a stable. The dust sampling rate and the concentration of MRSA in the sampled dust decreased after 5days of sampling. Sampling using the GSP can be performed for 1h without affecting the following half-life of MRSA. Sampling for MRSA using the EDC should not exceed 3days due to overloading and the die-off of MRSA. The measurement of OD may be used as a proxy measure for dust exposure. To obtain knowledge about potential exposure, samples should be taken repeatedly and in different areas within a stable section. Sampling method, sampling time and number of samples taken, but not force of airflow on the filter, influence the measured potential exposure to MRSA and dust.

An overview of heat stress relief with global warming in perspective.

Global warming seems more probable, whether as gradual warming or increased frequency of warmer episodes. The productivity of cattle in temperate countries will decline unless counteracting steps are adopted. The probability of pre-emptive breeding for maintaining temperate breed performance coupled with heat stress tolerance is too low to be adopted for counteracting warming. The expected warming will mostly involve temperature increases. These will indirectly affect radiant heat gain in animals owing to reduced radiant heat dissipation from the body by convective heat loss, which results in an increased sensitivity to incoming radiant heat at higher air temperatures. These necessitate an emphasis on increasing convective heat loss by structure design and forced air flow by fans. Convective heat loss diminishes with increasing air temperatures. Evaporative heat loss remains the alternative. Evaporative cooling of the ambient requires partial enclosing of the space surrounding the animals and is limited by the humidity in ambient air. An alternative was developed of coupling forced ventilation with wetting of animal surface. The exchange of ambient air flowing on animal surface makes the evaporation practically independent of air humidity and the loss of heat from animal surface practically independent of the surface to air temperature gradient. The coupling of forced ventilation with wetting combination may be attained in various parts of the dairy farm, the holding area of the milking parlour, the feeding trip and the resting area. Each of these requires differing structural and technological adaptations. Climate and farming systems vary between locations which require specific solutions.

Evaluation of cooling capability of an eco-cooler: experimental and numerical analyses

In this work, the capability of reducing room air temperature using four conical shaped eco-coolers has been investigated experimentally. The eco-coolers have inlet and outlet diameters of 24.67 mm and 92.67 mm respectively and they have a taper angle of 7.62°. The experiments were conducted for five consecutive days from 29th May to 2nd June 2018 (local evening time) in a confined room where the recorded room air temperatures were 28-30 °C. A low power consuming external fan (5 W) was employed to force air flow through the inlets of the eco-coolers. From the experimental results, it has been observed that it is only possible to reduce the outlet air temperature up to 0.2 °C when the inlet air velocity is in the range of 0.12-0.14 m/s with a negligible air working pressure difference of 10 Pa. The performance of an eco-cooler for similar experimental inlet air velocities (0.1-0.4 m/s) and practically observed air working pressure differences created by a regular fan (25-800 Pa) has also been studied with the help of numerical simulation. Results from numerical simulation indicate that the maximum achievable temperature drop is around 0.34 °C to feel human-skin comfortable, keeping the outlet air velocity within 13 m/s.

Increase of seeding material quality of agrarian crops by the pneumatic electric separator

A detailed analysis of technical means and methods of seeds separation, as well as the research results of domestic and foreign authors, have proved that one of the perspective methods for getting of high quality seed material is the pneumatic and electric separation.The analysis of research works and the modern technical level of pneumatic separators showed that insufficient attention was paid to the study of aerodynamic separation of small-seed crops, especially, cereal grasses. By the conditions of separation in a vertical pneumatic channel the cereal crops change the area of the midlength section as to the air flow forces, and the probability was increased of getting of seeds with germs to a biologically defective seed without germs. To increase the quality of pneumatic separation one can by the selective orientation of seeds in mixture with longer axis perpendicularly to the flow of air. It is possible to achieve these conditions by the additional force action on seeds (as particles). The response of this force action could be different for a healthy seeds (with germs) and for a non-viable (without embryo) or a weed seed. Such a force effect on the particles of small-seed crop mixtures can be realized by creating of a homogeneous electric field in a separation channel. This requires a theoretical and experimental study of force action on particles during the process of separation, also justification of parameters and operating modes of the pneumatic electric separator. This study is the preconditions for design improvement of the pneumatic electric separator.

Impact of forced air flow upon introducing pesticides under conditions of lateral wind

Pesticide application is accompanied by its losses due to the drift of the droplets of the working liquid caused by the wind outside the treatment area, which reduces the efficiency of chemical protection and increases impact on the ecological state of the environment. Influence of the precipitating (i.e. top-down) air flow has been determined upon the reduction of the drift of sprayed liquid droplets under the impact of a lateral wind, as well as distribution of the sprayed liquid studied by weight and length depending on the pressure of the working fluid in systems of various sprayers. At speed side wind 5.0 m·s&lt;sup&gt;–1&lt;/sup&gt; and deposition of flow at a speed of 15 m·s&lt;sup&gt;–1&lt;/sup&gt; the amount of fluid that settled, increased to 30% for spray ST 110-02 and 12% for spray ID 120-02.

Mating disruption of &lt;em&gt;Cadra cautella&lt;/em&gt; in the presence of synthetic sex pheromone (Z, E)-9, 12-tetradecadienyl acetate (ZETA)

The almond moth Cadra cautella (Walk.) (Lepidoptera: Pyralidae) is difficult to control using insecticides. Female moth releases a sex pheromone identified as (Z, E)-9, 12-tetradecadienyl acetate (ZETA). Information on population management of C. cautella using pheromone is limited. Objectives of this study were to determine the effect of pheromone dose, population size and air flow on mating status of C. cautella. The unmated male and female adults were introduced into a cubicle, allowed mating, recaptured, and the females dissected to determine the presence of spermatophores indicative of mating. The moths exposed to pheromone doses had lower mating than untreated control. Mating disruption (MD) was higher at ZETA 4.5 mg/45 mL than other doses. For each population size tested, moths exposed to synthetic pheromone had lower mating than their respective control. Insect population sizes 10 and 20 had higher MD with the natural air flow than 30 moths/3.375m3. In contrast, under forced air flow, MD was similar across all the population sizes tested. This study reveals that MD using ZETA is possible for controlling C. cautella. Future research should address its usage under warehouse conditions having different complexities.

Numerical modeling of transient heat transfer in heat storage unit with channel structure

The subject of the paper is a heat storage unit made of repeatable modules that are used in solar installations for heat accumulation. The accumulator may be a separate unit, or it may be a building wall insulated on the inner and outer surfaces. It is a heat accumulator with dynamic discharge using of forced air flow through the channels. The transient temperature field in the walls of the channels was modeled using control volume based finite element method (CVFEM), and the heat transfer in the flowing air was modeled by finite volume method (FVM). The CVFEM was chosen for the construction of a model of the heat storage unit, due to the ease of modeling a solid filling of a heat storage unit with a complex shape. In the numerical model of the heat storage unit, it was taken into account that air flow in the heat storage unit can be laminar, transitional or turbulent. The finite volume method was improved to obtain accurate air temperature distribution even with a small number of finite volumes. The results of calculations of the heat storage unit obtained using the proposed numerical model were compared with the results of CFD simulation and experimental data.