Airflow Velocity Research Articles

Computer-Aided Neuro-fuzzy Algorithm for Prediction of Ginger(Zingiber officinale) Rhizome Drying

Neuro-fuzzy modeling technique has been used for the development of computer-based adaptive process control systems for most postharvest operations instead of convectional mechanistic modeling technique owing to its good prediction without prior knowledge of process operation. Therefore, adaptive neuro-fuzzy inference system (ANFIS) modeling and prediction of ginger (Zingiber officinale) rhizome moisture content in a forced convective tray dryer was investigated in this study. Computer codes for an exhaustive search and grid partitioning were written in the Matlab software environment and used for the analysis of experimental data obtained from the ginger rhizome drying experiment. The data were trained and checked using the grid-partitioning ANFIS method for the development of neuro-fuzzy network for ginger drying prediction. The prediction accuracy of the network was evaluated by varying input and output Membership Function (MF) types. The exhaustive search analysis shows that drying time (DT) has the highest effect on the moisture content, followed by air drying temperature (ADT), air relative humidity (ARH), and air flow velocity (AFV). Moreover, combination of DT and ADT as two interactive variables; and combination DT, ADT and ARH as three interactive variables show highest effect on ginger moisture content removal during the process. Generalized bell (gbell) MF with two MF for each input variable and constant output MF 2 type were obtained as the best ginger drying ANFIS network with corresponding R and MSE of 0.9667 and 0.0971, respectively. Therefore, this study shows the reliability of the ANFIS model for the prediction of ginger rhizome drying in a tray dryer.

Integrating full fan morphology and configuration in three-dimensional simulation of air-cooled proton exchange membrane fuel cell stack

The internal water and thermal state and performance of an air-cooled proton exchange membrane (PEM) fuel cell stack are strongly determined by the fan arrangement and operational characteristics. This study presents an innovative method to investigate the influence of fan on stack performance through integration of fan’s full morphology, including the fan blade, grill between the fan and stack, etc. into a three-dimensional (3D) multiphase stack model. The multiple reference frame (MRF) model is implemented to simulate the air flow field caused by the rotation of fan and the multiple transfers coupled with electrochemical reactions is considered in the 3D stack model in detail. Through this integrated model, the influence of the air supply mode, fan number and duty ratio on stack performance and the distribution characteristics are investigated in detail. It is found that the air flowing into each cell in the fan-cooled stack is highly non-uniform, which increases the variations of oxygen concentration, temperature, and voltage in the stack. In comparison with the blowing mode, the suction mode helps to promote the uniformity of air supply with a lower air flow velocity.

Experimental study on forced ventilation in dead-end mine working with various setbacks of the ventilation pipeline from the working face

The study of airflow patterns at the ends of dead-end mine workings is crucial for optimizing underground mining ventilation systems. Understanding these patterns forms the basis for designing and implementing effective ventilation strategies.Previous studies have shed light on the behavior of the main vortex and the formation of stagnant zones in such environments, but these insights remain fragmented and call for a more systematic exploration to integrate them into a comprehensive theory.This paper presents the results of a thorough field investigation into the forced ventilation behavior in a dead-end mine working with a significant cross-sectional area (29.2 m2). We evaluated the impact of varying the setback distance of the ventilation duct’s end from the working face at intervals of 10, 15, 17, 19, and 21 m. The experimental design included precise measurements of turbulent airflow velocities at 25 carefully chosen points (in a 5x5 grid) for each setback distance, covering the area from the working face to beyond the end of the ventilation duct. This included additional measurements taken 1 meter and 10 meters past the termination of the ventilation duct, moving towards the entrance of the working area.The fieldwork was carried out in a typical dead-end stope at the Kupol gold-silver mine in the Chukotka Autonomous District, created by drilling and blasting.The volume of fresh air delivered to the working was maintained at a consistent rate of 17.4 m3/s across all scenarios, aligning with the mine’s standard air flow rate derived from the ventilation requirement for exhaust gases emitted by internal combustion engines of Load-Haul-Dump (LHD) machinery. With the duct’s terminal cross-sectional area at 0.8 m², this resulted in an inflow velocity averaging 21.75 m/s.Additionally, we included insights from three-dimensional numerical simulations performed in ANSYS Fluent, focusing on steady-state air movement and developed turbulence within the dead-end space. A comparative review of both empirical and modeled data shows that the ventilation jet, for all tested setback distances up to 21 m, successfully delivered air to the working face, where it then dispersed and initiated reverse flow patterns.These experiments led to the formulation of a linear relationship between the maximum relative velocity (compared to the initial jet velocity) at a distance of 1 m from the working face and a key geometric factor of the ventilation setup. This factor is the ratio of the duct’s setback distance to a characteristic dimension of the cross-sectional area, calculated as the square root of the cross-sectional area.

Non-thermal plasma for decontamination of bacteria trapped in particulate matter filters: plasma source characteristics and antibacterial potential

The aims of this study encompass the characterization of process parameters and the antimicrobial potential during operation of a novel non-thermal plasma (NTP) source in a duct system containing a particulate matter (PM) filter thus mimicking the interior of an air purifier. Simulating conditions of a long-term operation scenario, in which bacterial aerosols in indoor environments accumulate on PM filters, the filter surfaces were artificially inoculated with Escherichia coli (E. coli) and exposed to an air stream enriched with reactive species. Electrical power consumption, key plasma parameters, volume flow and air flow velocity, reactive gas species concentrations as well as inactivation rates of E. coli were assessed. The NTP operated at a gas temperature close to ambient air temperature and featured a mean electron energy of 9.4 eV and an electron density of 1∙1019 m−3. Ozone was found to be the dominating reactive gas species with concentrations of approx. 10 ppm in close vicinity to the PM filters. An inactivation rate of 99.96 % could be observed after exposure of the PM filters to the gas stream for 15 min. This inactivation efficiency appears very competitive in combating realistic bacterial aerosol concentrations in indoor environments.

The relationship between the resistance characteristics and structural parameters of the elongated filter cartridge in the dust collector

Due to the advantages of a large filtration area, elongated filter cartridges are gradually replacing filter bags in dust collectors. However, the production standards for these filter cartridges lack clarity in determining various parameters. Therefore, this paper combines experimental validation with computational fluid dynamics simulations to analyze the resistance characteristics of elongated filter cartridges, aiming to establish recommended parameter combinations for their optimal design. Single factor analysis and Response Surface Methodology (RSM) are employed for parameter optimization. The study establishes a quadratic regression model to predict resistance based on various filter cartridge parameters. Single factor analysis indicates that the optimal combination of length and pleat number is approximately diagonally distributed. The RSM ranks the factors' impacts on resistance as follows: length (L) > pleat number (N) ≈ pleat length (Pl) > filtering velocity (vf) > outer radius (R). The optimal parameter combination under global optimization is: N = 43, Pl=23 mm, R = 76 mm, L = 2 m. Additionally, the study analyzes the distribution of normal and tangential velocities of airflow on the filter medium surface to understand their impact on filter lifespan. Results indicate that tangential velocity has a significant impact on filter wear, and locations with higher tangential velocity are situated in the bottom region of the fold at the outlet.

Starch powder in short air contact time: Material moisture change, stickiness and deposition at different air relative humidity and temperature

Starch powder can get sticky and cause deposition in process, resulting in downtime and performance deterioration. Glass transition temperature (Tg) is a key aspect of semi-crystalline material stickiness, being function of material water content, and the surpass of material temperature above Tg is related to its stickiness. During pneumatic transport and process, in short air contact time, powders can exchange heat and water, which might change stickiness. Dairy powders were already assessed on stickiness tests replicating these conditions, but not starches. Potato and corn starch powders are investigated and stickiness, deposition and water content change are measured. Water content changed linearly with relative humidity. Deposition occurred on a plate at high and low air flow velocities and the deposition patterns correlate with the flow velocity profile. Corn starch presented higher stickiness and more deposition. Stickiness can be achieved by the combination of different air temperatures and relative humidities.

Investigation of a Wheel Liquid Desiccant Cooling System Performance via ANSYS CFX

A liquid desiccant cooling system is an alternative air-conditioning system with significant energy-saving potential. This system is commonly used in the industrial sector, such as in dehumidifiers. The key component of the liquid desiccant cooling system is its dehumidification performance. Therefore, a study on a liquid desiccant dehumidifier has been conducted to predict its performance using computational fluid dynamics analysis. In these simulations, the effects of the temperature of the liquid desiccant and the velocity of air flow on the absorption process between the liquid desiccant and air were studied. The same applies to the velocity profile, which helps determine the airflow pattern within the dehumidifier. The model was constructed using ANSYS FLUENT and Autodesk Inventor. The model is the rotary desiccant wheel dehumidifier which was used to dehumidified the air.. ANSYS CFX was used for simulating the velocity profile to achieve the airflow pattern in the dehumidifier. The volume of fluid was selected as the multiphase method for the second simulation process. The temperature and mass fraction of water were monitored within the air during the counterflow simulation between the liquid desiccant and the air. The liquid desiccant chosen for this study was LiCl. The simulations were conducted at specific air velocities, and the behavior within the dehumidifier was observed. The analysis results revealed that the air entering the rotary desiccant wheel dehumidifier experienced a drop in velocity after passing through the desiccant wheel in the middle. Additionally, turbulence occurred after the air passed through the wheel and the dehumidifier’s wall. Based on these findings, the design of an optimal dehumidifier and the selection of an appropriate air velocity for cooling can be carried out.

Artificial neural network for drying behavior prediction of paddy in developed chamber fluidized–bed dryer

After rice is harvested, it must be dried before its products can be stored. Therefore, this paper presented a novel and simple method for improving paddy drying process in a column fluidized bed dryer. Additionally, artificial neural network methods were applied to predict the drying behavior. The experiments were conducted under two different drying chamber characteristics (a conventional chamber and a chamber fitted with nozzle) and four different air flow velocities (3.03, 3.52, 4.12 and 4.85 m/s) at a drying air temperature of 60 °C. The results showed that the chamber fitted with the nozzle reduced the drying time by approximately 67, 52 and 38 % at the air velocity of 3.52, 4.12 and 4.85 m/s, respectively. The specified experimental conditions and the calculated moisture content of the paddy in this work were used as input and output data for the artificial neural network, respectively, to predict drying characteristics. The artificial neural networks were developed with various parameters, including activation function, sampling type, split ratio, number of neurons and epoch number. The optimal model provided the root mean squared error of 0.111 and the coefficient of determination of 0.999. The best prediction was observed in the model using rectifier activation function with a split ratio of 0.85, epoch number of 1800, and 50 and 90 neurons in the first and second hidden layers, respectively.

Experimental investigation of thermal characteristics on a new loop pipe model for passive cooling system

The heat pipes have the potential to be used as a passive cooling system (PCS) in thermal installations including nuclear facilities. In that context, this experimental study is correlated with the research on the new type of Loop Heat Pipe (LHP) as the PCS. This work aimed to study the characteristics of LHP with capillary pipe wick. The experiments involved varying the pool water temperature as evaporator heat load at 35, 45, 55, and 65 °C, filling ratio charged at 20, 40, 60, 80, and 100 % of LHP evaporator volume, and the flow air velocity to the fins in the condenser at 0, 1, 1.5, 2, and 2.5 m/s. The LHP was operated in sub-atmospheric conditions with an initial pressure of 2666.4 Pa. The results show that LHP has a stable two-phase natural circulation under all variations of heat loads, filling ratios, and air velocities tested. The results also show that display excellent thermal performance with the lowest thermal resistance of 0.0524 ± 0.0004 °C/W operating at the highest water temperature source, the highest filling ratio, and the highest air velocity. It is concluded that the LHP model with capillary pipe wick has similar thermal characteristics to other types of heat pipes. This wick function effectively in preventing vapor flow from the evaporator toward the condenser, and otherwise it can facilitate as condensate path from the condenser to evaporator. The stable two-phase natural circulation stability analysis showed that the LHP with capillary wick has very good thermal performance as heat absorber and heat releaser.

A novel thermal-fluid topology optimization of the frame mold for composite autoclave process

Frame mold serves as an important tool during autoclave process of composite panels. Its temperature uniformity plays a crucial role in guaranteeing the production quality. However, the temperature uniformity of mold usually has to be sacrificed during the design process for ensuring the stiffness of mold. To solve this problem, a novel design strategy is proposed in this study to optimize the heating airflow channels of mold with better temperature uniformity based on thermal-fluid topology optimization method. Firstly, the temperature and the airflow distribution characteristics of mold during autoclave process are investigated systematically based on the Computational Fluid Dynamic (CFD) simulation model. The result indicates that the uneven temperature distribution of the mold during autoclave process is significantly affected by the varying airflow velocity distribution inside the mold. Inspired by this, a thermal-fluid topology optimization method is developed to design the airflow channels of mold to achieve optimal mold temperature uniformity. The optimization result provides a novel configuration of mold in which a ‘wind deflector’ is incorporated inside the mold to alter the airflow pattern. Finally, the simulation results show that the optimized mold with a ‘wind deflector’ significantly improves the mold temperature uniformity by 16%. And experimental validation has applied to confirm the effectiveness of the results. Besides, the configuration of the optimized mold has good industrial application prospects for its convenient installation process and low cost.

Experiments and CFD simulation of downwash airflow and fog distribution discharged from a single-rotor UAV fitted with a pulse-jet thermal fogging machine

A single-rotor UAV fitted with a pulse-jet thermal fogging machine was developed. Computational fluid dynamics (CFD) was employed to simulate the downwash airflow and fog distribution of a single-rotor UAV fitted with a pulse-jet thermal fogger. The developed CFD models were validated in three steps by comparing the calculated results with the measurement experiments. Predicted air velocities of the single-rotor UAV downwash airflow agreed well with measured velocities. The model was also able to predict the fog droplet deposition density of the pulse-jet thermal fogger alone, and fitted to the single-rotor UAV, with the relative errors within 20% and 30%, respectively. The validated CFD model was then employed to investigate the effects of the headwind, crosswind and UAV operating height on the downwash airflow and the fog distribution. Results indicated that when the pulse-jet thermal fogging machine was mounted on the UAV, crosswinds needed to be avoided. At the UAV flight speed of 2 m s−1 and natural wind speed of 1 m s−1, a modest headwind appearance could help improve thermal fogging efficiency at different operating heights. The results have important research value and practical significance for improving the pesticide efficiency of UAV sprayers.

An experimental evaluation of drying banana slices using a novel indirect solar dryer under variable conditions

Novel thermal characteristics of drying banana slices in an indirect dryer are presented for four different experimental drying conditions in the forced convection mode. The novel characteristics include measuring the airflow velocity in the drying chamber, measuring the thermal profiles in different trays comprehensively and measuring the relative humidity under different conditions. Two tests are carried for 16 h in two consecutive days (8 h per day for each test). The first test is on acloudy day followed by a sunny day, while the second test is carried out on two consecutive sunny days. Tests 3 and 4 are 24 h tests with high (0.23 m/s) and low (0.11 m/s) average drying chamber airflow velocities under good solar radiation conditions. The maximum temperatures obtained in the collector and the drying chamber are around 80 and 48 °C, respectively, for the 16 h tests. Significantly lower collector and drying chamber temperatures are obtained due to cloudy conditions. Maximum collector temperatures are around 84 and 95 °C for the high and low average airflow chamber velocities for the 24 h tests. The corresponding maximum temperatures in the drying chamber are around 50 °C for the 24 tests. The final moisture ratios are 0.26 (cloudy and sunny days) and 0.20 (two sunny days), respectively, for the 16 h tests. These final moisture ratios are lower than those obtained for the 24 h tests which are 0.32 and 0.28, respectively. Increasing the drying chamber airflow velocity results in faster moisture removal during sunshine hours for the 24 h tests. For tests 1, 2, 3 and 4, the maximum average collector efficiencies during the sunshine period are around 60, 80, 40 and 10 %, respectively. The average drying efficiencies for the total solar drying period for tests 1,2,3 and 4 on day 1 are 6.9, 6.9, 5.5 and 5.7 % respectively. These values are comparable, suggesting that the average collector powers, airflow velocities and efficiencies have a very small effect on the average solar drying efficiency for the whole drying period. The quality of the bananas slices mainly in terms of the colour and shape is also compared with previous studies and commercially available products. A reasonably acceptable quality product is obtained.

Full-scale experimental, numerical, and theoretical research on the spatio-temporal evolution of the flow structure in longitudinal and semi-transversal ventilated tunnels

This paper presents full-scale experimental, numerical, and theoretical research on the spatial and temporal structure of airflow for different modes of ventilation system operation in a road tunnel. The tunnel under investigation is equipped with a semi-transverse ventilation system. There are 19 pairs of axial jet fans in each tunnel tube and 164 air supply vents on both sides of a tube located just above the road surface. A set of seven stand poles with mounted vane anemometers were arranged along the tunnel tube axis. Different configurations of axial jet fans and air supply vents were employed, and changes in airflow velocity were recorded. Since the main objective of the study is to achieve a deeper understanding of the examined phenomena, a numerical model of the flows in the tunnel was built, and the acquired data was used to validate it. Some theoretical considerations are provided and also validated. All of this together reveals a very uneven distribution of longitudinal air velocity along the tunnel axis. Then, time constants when switching the fans on and off are determined. It is shown that the time needed to achieve a stable flow after the fans are turned on is in the order of five minutes, and the decay time after the fans are turned off is much longer; it takes about 15 min to calm down the flow. Next, it is determined that the transverse air supply significantly changes the airflow structure: the average longitudinal air velocity at the inlet portal was up to 25% lower than without it, while values at the outlet portal were similar. Finally, it is indicated that axial fans that operate in the suction mode are similarly efficient to those in the pumping mode.

Analysis and optimization of effect factors of refrigeration performance of portable micro-refrigerator

The objective of this study was to ascertain an efficient portable cold container, considering the constrained space, low airflow velocity, and uneven heat distribution of a micro-refrigerator, which lead to in insufficient heat dissipation and low refrigeration efficiency. A thermoelectric micro-refrigerator model with a volume of 9083.8 cm3 was established under forced convection heat transfer conditions. Through single-factor and response surface experiments, the impact of thermoelectric elements configuration on refrigeration efficiency was identified. These elements include the input current of the Thermo Electric Cooler (TEC), the derating factor (actual power) of the cooling fan, and the height of the heat sink fin.The results indicate that optimizing the refrigeration conditions significantly enhances the refrigeration efficiency of the micro-refrigerator. At an ambient temperature of 25℃, with a fan derating factor of 0.77 (corresponding to an actual power of 0.8218 W), a heat sink fin height of 59.15 mm, and a TEC input current of 5.09A, under stable conditions,the cold side temperature can reach −11.3 ℃. The hot side temperature is 38.2 ℃, consistent with the response surface experiment result. Numerical simulation under these conditions reveals a cold side temperature of −12.4 ℃ and a hot side temperature of 41.9 ℃, showing a 9.7 % difference from the experimental results. The simulation data further demonstrate that the vertical arrangement of the cooling fan and heat sink can achieve a cold side temperature of −12.9 ℃, effectively maintaining the hot side temperature below 40 ℃. The thermoelectric system investigated in this paper holds promising potential for applications in portable fresh-keeping and refrigeration.

Multi-functional nanofibrous membrane with antibacterial property for highly effective capture of PM0.3 and hydrogen sulfide

In order to reduce the possible harm caused by air pollution, including particulate matters (PM), harmful gases and airborne pathogens, high-efficiency air filtration materials are attracting more and more attention. Therefore, multifunctional materials that can filter these pollutants and kill pathogenic bacteria simultaneously are urgently desired. Herein, a copper-coordinated nanofibrous membrane, named PAN-P-Cu, was successfully prepared based on polyacrylonitrile (PAN) nanofibers grafted polyethyleneimine (PEI) by electrospinning and coordination assembly method. The PAN-P-Cu showed high filtration efficiency (99.9%) towards PM0.3 under an airflow velocity of 5.3 cm s−1 and high filtration efficiency (99.94%) towards PM10, respectively. Importantly, used membrane could be regenerated by a simple washing process. Moreover, PAN-P-Cu possessed removal property of 60 mg g−1 for hydrogen sulfide through the occurrence of chemical reactions. Furthermore, the PAN-P-Cu also exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus (>99.99%). This work may provide new insights on designing high-performance and multi-functional air filtration materials for public health protection in complicated environments.

Dynamic transport characteristics and performance response of commercial-size polymer electrolyte membrane fuel cell stack: An experimental study

The stability and durability of polymer electrolyte membrane fuel-cell stacks are closely related to their dynamic performance responses and internal transport characteristics, particularly for commercial-size stacks in automotive applications. In this study, the dynamic behaviors of a 10-cell stack (active area: 310 cm2) are investigated under various loading/unloading processes and cathode stoichiometric ratios; additionally, the joint influence of these two factors is analyzed. Voltage hysteresis is observed, and the dominant roles of dynamic oxygen, membrane water, and liquid transport are elucidated. The results indicate that the electro-osmotic effect dominates and results in anode-membrane dehydration as the loading process proceeds (>1.5 A cm−2). A larger airflow velocity enables faster downstream oxygen delivery, causing the oxygen concentration to reduce initially and then increase gradually with time after loading, thus voltage undershoots appear. Voltage hysteresis is enabled during the continuous loading/unloading/loading process owing to the difference in accumulated liquid water drainage ability after step loading and unloading. Although the synergistic loads and cathode stoichiometric ratio variations enable less cell-performance deterioration than that on contrary strategy, the dynamic characteristics are much more unstable and more likely to induce cell-stack failure and durability problems. This study provides insights into the dynamic transport characteristics in a commercial-size fuel cell stack and presents a guidance for control strategy development.

Environmentally friendly recycling process for crystalline silicon photovoltaic modules: Airflow separation and AlCl3·6H2O + H2O2 etching system

The disposal of crystalline silicon photovoltaic modules (c-Si PV modules) at the end of their service life (EoL) is a pressing issue that requires attention. In this study, an environmentally friendly and efficient recycling method was proposed, involving pyrolysis, airflow separation, and AlCl3·6H2O + H2O2 etching. After removing the backsheet, EoL c-Si PV modules were pyrolyzed to eliminate ethylene vinyl acetate (EVA) as an encapsulant. A gas/solid fluidized bed was employed to separate solar cells and glass particles mixed together after pyrolysis. The findings of the study indicate that, under specific parameters including a bed height of 6 cm, an airflow velocity of 58.82 m3/(L·h), and a separation time of 5 min, the separation process achieved remarkable efficiencies. Notably, the recovery efficiency and product purity for samples with particle sizes of d > 4 mm and 2 < d ≤ 4 mm were recorded at 100 % / 99.37 % and 100 % / 95.50 %, respectively. The experimental results demonstrated that, under the conditions of 0.6 mol/L AlCl3·6H2O, 2 % H2O2, and a temperature of 80℃ for 30 min, a significant removal of 95.32 % for Ag and 99.77 % for Al was achieved. This finding illustrates the effectiveness of the selected reagents in the etching process. The insights gained from this paper contribute valuable knowledge to the optimization and understanding of the separation and etching processes employed in solar cell separation.

Relationship between cross-sectional plane and corresponding morphology in an immiscible alloy powder with core-deviated structure

Immiscible alloy powders with core/shell structure have recently garnered considerable interest due to their excellent industrial performance. However, a frequently observed yet often overlooked feature is the presence of core-deviated structure in various cross-sectional planes of the powder. To date, limited research has been conducted on this structure and its origin, leaving the formation mechanism unclear. Gaining a comprehensive understanding of this mechanism is crucial for advancements in powder materials research. In this study, we first analyzed the solidification microstructures of Fe-68 wt.%Sn alloy powders, followed by a numerical analysis of airflow and internal temperature fields within a powder during the free-falling process. Our findings revealed that the average airflow velocity on the windward side is faster than that on the leeward side, causing the highest temperature point within the powder to shift towards the leeward side over time. This phenomenon is fundamentally linked to the formation of the core-deviated structure. Furthermore, we explored the relationship between cross-sectional planes and potential microstructures, demonstrating that the final observed structures are strongly influenced by the position and orientation of the cross-sectional plane. Additionally, the core deviation distance was theoretically predicted and found to be consistent with experimental results in Fe-68 wt.%Sn powders. This research provides valuable insights into the actual solidification process of immiscible alloy powders and contributes to the development of specialized structural materials.

Design and evaluate the performance of a mechanical system for the release of Harmonia axyridis adults.

Harmonia axyridis (H. axyridis) is the natural enemy of many aphid species. Traditional manual release of H. axyridis adults requires substantial manpower, and release efficiency is low. Automatic mechanical devices can improve the efficiency of delivery. Based on H. axyridis adults' morphological size, a prototype release system for H. axyridis was designed, which considered the adhesion characteristics of H. axyridis adults. According to the measured physical characteristics of H. axyridis adults, the structural parameters of the mechanical system for the release of the H. axyridis adults were determined. The relationship of the quantity of release, the impeller rotating speed, and the time for the release of H. axyridis adults were constructed. The mechanism can quantitatively adjust the number of H. axyridis adults to meet a certain H. axyridis-aphids ratio. Combining the image processing technology with the camera function of a mobile phone, the maximum cross-sectional area method was used to count the H. axyridis adults in the designated area. Results showed that the impeller rotating speed had a significant effect on the survival rate of the H. axyridis adults. When the airflow velocities were 29.5 m/s and 38.3 m/s, the survival rates of the H. axyridis adults were 93.8% and 94.5% at 4.2 rpm. The adhesion rate of the H. axyridis adults was 2.5%-4.6%. This work will provide technical support for the research of biological control.

Simulation and experimental research on the optimization of airflow organization and energy saving in data centers using air deflectors

The airflow organization of the data center directly affects the temperature control performance and the energy efficiency of the cooling equipment. The servers at the bottom of the rack usually suffer from insufficient airflow rate and poor cooling effect. This is because of the limited distance between the bottom servers and the perforated floor, and the small horizontal velocity of the supply air flow. This study aims to improve the uniformity of the cooling airflow in the vertical direction of the rack by the air deflectors, thereby further improving the overall airflow organization in the data center. The size and installation of the deflectors in the data center were optimized according to both the experiment and numerical simulation results. From the results, it is recommended to install the deflector with a width of 100 mm at an angle of 45° under the perforated floor for the rack with the single-side airflow supply. For the rack with the double-side airflow supply, the width of the deflector should be 100 mm and installed at an angle of 30° to the perforated floor to achieve the best airflow distribution. Consequently, the intake airflow rate for the bottom servers significantly increased, and the occurrence of the local hot spots was effectively reduced. The numerical simulation of the airflow organization with and without the deflector was conducted by ANSYS. The results show that, the installation of the deflectors increased the inlet airflow rate for the rack by 16.98% and improved the energy efficiency of the dater center air conditioners by 1.98%.