Optimal Spray Research Articles

Experimental investigation on the application of cold-mist direct evaporative cooling in data centers

The rapid development of the internet era has driven the construction of numerous data centers worldwide. In hot climate, data centers consume significant energy for cooling. Cold-mist direct evaporative cooling offers a natural cooling solution that can help reduce this energy consumption. This study investigates the temperature and relative humidity changes of natural high-temperature air after being cooled using a cold-mist direct evaporative cooling test bench. The effects of several control factors such as spray angle, spray flow rate, and air speed on the cold-mist direct evaporative cooling performance was systematically examined. The findings revealed that: (1) the optimal spray angle for cold-mist direct evaporative cooling treatment air is 65°; (2) high-temperature air between 27 °C and 37 °C can be cooled to 23.57 °C – 25.58 °C after cold-mist direct evaporative cooling treatment, with relative humidity levels of 67.0 % – 78.8 %, meeting the air supply requirements for data centers; (3) the proposed approach could reduce the data center energy consumption by 14 % – 41 %, while extending the annual natural cooling period by 3.16 % – 20.45 %.

Bonding performance and construction parameters of low-rebound shotcrete

Abstract Shotcrete has the advantages of short setting time, high early strength, simple process and flexible operation methods. It is mainly used as temporary support in domestic highway tunnels. This study investigates the development of low-rebound shotcrete for tunnel construction by adding silica fume and fly ash into the mixture. Sandstone and limestone were employed to simulate the surrounding rock. The workability and mechanical properties of the shotcrete were evaluated based on slump tests, rebound rates, compressive strength measurements, and bonding strength tests between the surrounding rock and the shotcrete. Furthermore, the research investigated construction techniques, with an emphasis on spraying distance, shrinkage angle, and wind pressure, and optimized these parameters for practical engineering uses. The outcomes demonstrate that the addition of silica fume enhances the mechanical properties of the shotcrete and reduces rebound. It was discovered that optimal spraying distance was between 1.2 m and 1.5 m, with the optimal wind pressure at 0.5 m, and the ideal shrinkage angle at 6°.Research on low rebound shotcrete is of great significance for improving construction quality, construction efficiency and engineering structural performance, and also meets the requirements of sustainable development.

Numerical Investigation of Film Formation Characteristics and Mechanisms through Airless Spraying on Spherical Surfaces

This paper focuses on key engineering issues, particularly the overall turbulent transport of paint spray and coating film distribution characteristics, in the process of airless spraying film formation. By deeply considering the geometric features of spherical surfaces and their impact on the near-wall region of the flow field, an airless spraying film formation model consisting of the Eulerian multiphase model, the realizable k–ε turbulence model, and the Eulerian Wall Film model was established. Through numerical simulations of static spraying on the inner and outer walls of spherical surfaces with different radii, the influence of geometric features on the spray flow field and film formation characteristics on spherical surfaces was investigated. Subsequently, based on numerical simulations of dynamic spraying on different nozzle trajectories, the film formation characteristics were analyzed, and the optimal spray trajectory planning method was determined. Additionally, this study examined the coating distribution characteristics during dynamic spraying on spherical surfaces with varying geometric dimensions. Finally, a kind of chlorinated rubber anti-corrosion primer was chosen to carry out spraying experiments, which validated that the airless spray coating model and the corresponding numerical simulation methods established in this paper were reasonable and feasible for investigating the film formation characteristics on spherical surfaces. This work is expected to further promote the application of airless spray techniques in machinery, automotive, shipbuilding, and aviation industries.

Optimizing epoxy asphalt tack coat formulations for improved adhesion and working performance of ultrathin wearing course

Insufficient adhesion between ultrathin wearing courses (UTWCs) and substrate layers can result in pavement distress. Epoxy asphalt exhibits potential as a tack coat due to its high bonding strength and thermal stability. However, its rapid curing may pose challenges to construction schedules. This study aimed to optimize the formulations of epoxy asphalt tack coats (EATCs) to enhance the interfacial adhesion and working performance of UTWCs. The adhesion of EATCs was evaluated through rotational viscosity and tensile tests. Design parameters were optimized using analysis of variance and microscopic tests. Road performance was assessed via interlayer shear and tensile testing on three pavement structures. The results indicated that the curing agent strongly influenced the properties and curing kinetics of EATCs. Formulations containing complex polysebacic polyanhydride (CPSPA-EA) exhibited superior bonding while meeting construction schedules. Microscopic analysis of CPSPA-EA revealed a stable crosslinked network formed at 30% binder dosage. The amount of spraying significantly impacted the adhesion in UTWC structures. The optimal spraying amounts were 0.60 kg/m2 for asphalt concrete (AC-13), 0.55 kg/m2 for stone matrix asphalt (SMA-13), and 0.40 kg/m2 for cement concrete substrate layers. These findings presented an optimization framework for designing EATCs to enhance UTWCs working and long-term performance through balanced tack formulations and application parameters.

Al-based amorphous coatings by warm spraying: Numerical simulation and experimental validation

Al-based fully amorphous coatings with low porosity were successfully produced via warm spraying, combining numerical simulation and experimental validation. A warm spray gun model, employing computational fluid dynamics, was developed to simulate the warm spraying process. The study delved into the effects of reactant flow rate, oxygen/fuel (O/F) ratio, coolant flow rate, spray distance, particle size, particle shape, particle injection velocity, and particle injection angle on the gas flow field parameters (pressure, temperature, and velocity) and particle in-flight behaviors (temperature, velocity, and in-flight trajectory). The optimum spraying parameters (OSP) predicted by the simulation results were determined: 0.008740 kg/s for reactant flow rate, 2.7 for the O/F ratio, 0.007356 kg/s for coolant flow rate, 142 mm for spraying distance, 10–35 μm for particle size range, spherical for particle shape, 10 m/s for particle injection velocity, and 0° for particle injection angle. Subsequently, warm spraying experiments based on the OSP yielded Al-based fully amorphous coatings with a porosity of 0.08 %. This work provides valuable insights for the production of Al-based fully amorphous coatings with minimal porosity through warm spraying.

A multistage biogas slurry reflux and spray anaerobic digestion reactor for high solid anaerobic digestion: Performance and application evaluation

In this study, a new vertical plug-flow continuous dry anaerobic digestion reactor equipped with a spray percolation system was designed for rice straw and cow manure in dry AD. The findings indicated that the methane yield was 290.63 ± 19.16 mL/g VS when the optimal spray time (9 times/d) was used in batch AD. In addition, the results of continuous experiments under optimal spray time conditions showed that the volumetric methane production rate of the system was 1.55 L/(L·d) when the organic loading rate was 20 g VS/(L·d). In addition, hydrolysis and acidification steps were enhanced. This study demonstrated the potential of the new reactor for stable operation of high OLR dry AD. Digestate is already used as a substitute for synthetic fertilizers precisely because of the environmental benefits associated with its agronomic use.

Effect of HVOF parameter on titanium oxide (TiO2) coating characteristics on AZ81 magnesium alloy

High-velocity oxy-fuel (HVOF) coating to enhance the erosion, wear, and corrosion-resistant properties crucial for orthopedic applications. HVOF is distinguished for its capability to provide surfaces with a dense and superior finish. Porosity and hardness serve as vital process variables in assessing performance. This current study aims to optimize HVOF process parameters to minimize porosity values in titanium oxide (TiO2) coatings applied on AZ81 magnesium substrate. Oxygen flow, liquefied petroleum gas (LPG) flow, coating material feed rate, and spray distance were selected due to their significant impact on the coating quality. Statistical techniques such as response surface methodology (RSM), analysis of variations, and design of experiments (DoE) were employed to obtain the necessary results. The findings indicate that LPG flow has the most significant influence on coating quality, followed by standoff distance, oxygen flow rate, and feed rate. The coating obtained using optimal spray parameters exhibits a lower surface porosity of 0.86 vol.% and achieves a greater hardness of 922 HV. This has been confirmed through validation via the response graph. Consequently, the optimized parameters for TiO2 deposit entail an oxygen flow rate of 266 lpm, an LPG flow rate of 68 lpm, a powder feed rate of 35 g/min, and a spray distance of 236 mm. KEY WORDS: High-velocity oxy-fuel, Response surface methodology, Porosity, Hardness, AZ81 Magnesium alloy, Titanium oxide Bull. Chem. Soc. Ethiop. 2024, 38(6), 1869-1886. DOI: https://dx.doi.org/10.4314/bcse.v38i6.28

Complex formation and stabilization of Z‐isomer‐enriched astaxanthin esters derived from Haematococcus lacustris with water‐soluble carriers via spray drying

AbstractTo enhance the water solubility and bioavailability of astaxanthin esters, inclusion complexes of Z‐isomer‐enriched astaxanthin esters with water‐soluble carriers were prepared using a spray drying technique. A food‐grade Haematococcus alga extract was used as the source of astaxanthin esters, and the Z‐isomerization was performed via direct heating of the extract. Polyvinylpyrrolidone (PVP) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) were used as water‐soluble carriers. The effects of spray drying conditions on the encapsulation efficiency of astaxanthin esters in the carriers and the total Z‐isomer ratio of encapsulated astaxanthin esters were investigated, and the physical properties and storage stability of the resulting composites were evaluated. Under optimum spray drying conditions, efficient production of highly water‐soluble Z‐isomer‐rich astaxanthin esters was achieved in both carriers: >95% encapsulation efficiency and >55% total Z‐isomer ratio. The physical properties, such as surface morphology and particle size distributions, of the resulting particles differed significantly between PVP and HP‐β‐CD. Storage tests demonstrated that the formulated Z‐isomer‐rich astaxanthin esters were highly stable. Our findings will contribute to the practical applications of Z‐isomer‐rich astaxanthin materials.Practical Applications: The formulation technology developed in this study has the potential to address the industrial challenges of using astaxanthin, that is, low water solubility and low bioavailability. Furthermore, the low storage stability of astaxanthin Z‐isomers, which hinders their industrial use, can be solved simultaneously. The resulting Z‐isomer‐rich astaxanthin powders are expected to be used in a wide range of applications, including nutraceuticals, cosmetics, and animal feeds.

Deep learning guided variable rate robotic sprayer prototype

This paper presents the development of a robotic sprayer that combines artificial intelligence with robotics for optimal spray application on citrus nursery plants grown in an indoor environment. The robotic platform is integrated with an embedded firmware of MobileNetV2 model to identify and classify the plant samples with a classification accuracy of 100 % which is used to dispense variable rate spraying of pesticide based on the health status of the plant foliage. The disease detection model was developed through the edge impulse platform and deployed on Raspberry Pi 4. The robot navigates through an array of plants, stops beside each plant, and captures an image of the citrus plants. It feeds the image into the deployed embedded model to generate a disease inference that informs the variable rate application of spray during real-time actuation. To test the spraying performance of the prototype within the growing environment, water sensitive cards were placed in each plant's canopy. After spraying, the samples of water sensitive cards were collected and quantified using a smart spray app to determine the classification accuracy as well as the extent of spray coverage on the citrus samples. The robot spray coverage results show an average spray coverage of 87 % on lemon foliage when compared with 67 % for navel orange, during the spray performance test of the robot.

Spray performance simulation and experiment analysis of a greenhouse fixed-pipe twin-fluid cold fogger with different nozzle settings.

High-efficient pesticide application equipment for protected cultivation is scarce. In response, a fixed-pipe twin-fluid clod fogger (FTCF) was proposed as a potential solution. To investigate the optimal nozzle layout and spray performance, a computational fluid dynamics (CFD) model was used to study the airflow distribution and spray deposition of a FTCF with different nozzle settings using the Euler-Lagrange approach. Specifically, two piping configurations, middle-cross-inverted (MCI) and bilateral-malposed-opposite (BMO), were combined with three nozzle spacings (2 m, 3 m, 4 m) resulting in six nozzle settings. Additionally, a greenhouse spray trial was conducted to test the performance of FTCF with the selected nozzle settings and to validate the model. The simulation results revealed that MCI piping configuration exhibited a stronger airflow disturbance compared to BMO configuration, indicating a more significant air-guided effect in the MCI configuration. Combining this finding with the ground droplet distribution analysis of MCI piping configuration, it was observed that MCI-2 m had the lowest coefficient of variation (CV) for ground deposition (20.56%). Consequently, MCI-2 m was determined as the most optimal nozzle setting. Verification results demonstrated a high consistency between experimental and simulated spray deposition results. The FTCF system effectively generated a three-dimensional airflow field throughout the greenhouse environment. Furthermore, jet flow produced by FTCF disrupted the overall airflow pattern within the greenhouse space which facilitated droplet suspension and dispersion. This study provides valuable insights and innovative ideas for enhancing pesticide application technologies in protected cultivations. © 2024 Society of Chemical Industry.

Microencapsulation of Yeast Cells and Its Potential Usage as a Post-Harvest Biocontrol Agent for Citrus Storage

In this study, yeasts isolated from citrus groves, trees and leaves were identified, phylogenetic analyzes were performed and their antifungal effects were determined. Wickerhamomyces anamolus (M72), Meyerozyma guilliermondii (M77), and Pichia kudriavzevii (M74) species were identified and were found to have antifungal effects against P. digitatum and P. italicum. Pichia kudriavzevii (M74), which has the highest antifungal effect, showed 67% and 62% inhibition rates against P. digitatum and P. italicum, respectively. An encapsulation study was carried out using a microencapsulation process to ensure that the M74 strain, which has the most antifungal effect, is long-lived enough to be a biopesticide. The optimum spray drying process parameters as well as the optimum concentration values of wall materials were investigated in the spray drying process for the microencapsulation of Pichia kudriavzevii (M74) through the Taguchi methodology. The formulation containing 0.1% sodium alginate (SA) and 10% corn starch (CS) showed a good performance in the inhibition of P. digitatum, a mold that causes losses in orange, thanks to its high percentage of viability (73%). The inhibition percentages may indicate that this formulation may be a candidate to be considered as a potential alternative application to synthetic fungicides on orange fruits for the effective control of P. digitatum mold.

Study on plant protection unmanned aerial vehicle spraying technology based on the thrips population activity patterns during the cotton flowering period.

Over the years, thrips have transitioned from a minor nuisance to a major problem, significantly impacting the yield and quality of cotton. Unmanned aerial vehicles (UAVs) for plant protection have emerged as an effective alternative to traditional pesticide spraying equipment. UAVs offer advantages such as avoiding crop damage and enhancing pesticide deposition on the plants and have become the primary choice for pesticide application in cotton fields. In this study, a 2-year field experiment found that the thrips population in a cotton field in Xinjiang, China, exhibited gradual growth during the early flowering phase, peaking in late July. The thrips population gradually shifted from the lower canopy to the upper canopy as the cotton flowers opened layer by layer. From 09:00 to 11:00 (GMT+8) and 19:00 to 21:00 (GMT+8), thrips mainly flew outside the flowers, while from 17:00 to 19:00 (GMT+8), they mostly inhabited the inner whorls of flowers. The insecticides 10% cyantraniliprole oil dispersion and 10% spinetoram suspension concentrate, sprayed by UAV, had the best control effect on thrips, with 80.51% and 79.22% control effect after 7 days of spraying, respectively. The optimal spraying time for 10% cyantraniliprole oil dispersion was 19:00 (GMT+8), and the control effect on thrips reached 91.16% at 7 days of spraying. During the cotton flowering period, thrips inhabited flowers in the evening and flew outside during the day. The best control effect on thrips was achieved with UAV-sprayed 10% cyantraniliprole oil dispersion at 19:00 (GMT+8).

Multi-parameter coupled optimization of Al6061 coating porosity based on the response surface method

The objective of this study is to study the multi-particle deposition process of cold spray through numerical simulation methods and to use multi-factor coupling to optimize the porosity of Al6061 coating to more accurately characterize the real cold spray deposition process. This study aimed to predict and optimize the porosity of Al6061 coatings using numerical simulation methods. The tasks to be solved are: to nest the multi-particle model established by the Python script in the CEL deposition model to simulate the cold spray deposition process. A multi-parameter function with particle temperature, substrate temperature, and particle velocity as independent variables and Al6061 coating porosity as dependent variables was established. The response surface analysis method was used to predict the optimal spraying parameters and coating porosity of Al6061 coating. The methods used are as follows: optimize the porosity of the coating through multi-factor coupling through response surface analysis; use a multi-particle model established through a Python script to be nested in the CEL deposition model to simulate the deposition process of cold-sprayed Al6061 multi-particles. To characterize the coating porosity more accurately, the average value of multiple groups of samples was taken as the final coating porosity value. Conclusions. the porosity value of Al6061 coating obtained by the prediction model is 1.969%; Under the influence of multi-factor coupling, particle velocity has the greatest impact on the porosity of the Al6061 coating, and the substrate temperature has the least impact. Optimum spraying parameters: particle temperature 649.692K, substrate temperature 536.437K, and particle velocity 672.385m/s. Under the optimal spraying parameters, the porosity value of the Al6061 coating is 1.91875%; The error between the predicted value and the actual value obtained by numerical simulation is only 2.55%.

Supersonic plasma-sprayed TiO2 coating: Performance optimization based on response surface methodology and tribological properties

This study investigated the microstructure and tribological performance of TiO2 coating prepared through the plasma-spraying of TiO2 on an aluminum alloy (ZL109) surface. Box–Behnken design was employed to calculate the optimal spraying parameters (spraying current: 439 A, spraying voltage: 129 V, and Ar flow rate: 117 m3/h). High-temperature tribological characteristics (T = 120 °C) were examined under varying loads (F = 100 N, 120 N, and 140 N). The scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis results revealed that the coating porosity decreased from 3.31 % to 0.31 % with the increase in the spraying voltage from 120 V to 130 V. Both powder and coating exhibited consistent elemental composition (Ti, O) and phase composition (TiO2, TiO, Ti2O3). During the spraying process, part of the powder was oxidized. The average coefficient of friction of the coatings varied from 0.05 to 0.08, and as the load increased, the wear mechanism of the coating changed from abrasion to adhesive wear and oxidation.

Numerical Simulation and Experimental Study of Gas–Solid Two-Phase Spraying of Dry Powder Fire-Extinguishing System Based on Fire-Extinguishing Inspection Robot

In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

From economic threshold to economic injury level: Modeling the residual effect and delayed response of pesticide application

Integrated Pest Management (IPM) poses a challenge in determining the optimal timing of pesticide sprays to ensure that pest populations remain below the Economic Injury Level (EIL), due to the long-term residual effects of many pesticides and the delayed responses of pest populations to pesticide sprays. To address this issue, a specific pesticide kill-rate function is incorporated into a deterministic exponential growth model and a subsequent stochastic model. The findings suggest the existence of an optimal pesticide spraying cycle that can periodically control pests below the EIL. The results regarding stochasticity indicate that random fluctuations promote pest extinction and ensure that the pest population, under the optimal cycle, does not exceed the EIL on average, even with a finite number of IPM strategies. All those confirm that the modeling approach can accurately reveal the intrinsic relationship between the two key indicators Economic Threshold and EIL in the IPM strategy, and further realize the precise characterization of the residual effect and delayed response of pesticide application.

Experimental investigation of spray cooling heat transfer with microcapsule phase change suspension

This paper reveals the spray cooling heat transfer mechanism with the microencapsulated phase change suspension as the working fluid based on an experimental investigation. The heat transfer performances between the spray cooling and jet impinging with suspension are compared. A series of key parameters affecting the heat transfer are analyzed, including suspension concentration, nozzle diameter, spray height, inlet temperature, and spray inclined angle. It concludes that the spray cooling of suspension has a stronger heat transfer capability relative to the jet impinging, but the pressure loss is correspondingly larger. Compared with the water, the spray cooling heat transfer of phase change suspension is superior owing to the latent heat ability of particle core, and the maximum improvement in the current tests is 33.9 %. However, excessive suspension concentration can result in the deterioration of heat transfer because of the larger viscosity. There is an optimal volumetric flow rate and an optimal spray height for the spray cooling, where a suitable spray cone angle is present so that the heating surface may be exactly covered by the liquid-film. The latent heat absorption characteristic of phase change core leads to the existence of an optimal spray inlet temperature, which is about 10 °C lower than the melting peak temperature of the particle core. For the cases of incomplete-coverage, the decrease of the spray inclined angle may enlarge the liquid-film covering area and thence improve the heat transfer. A theoretical analysis indicates that the suspension in current tests has a high complete-melting rate (σ ≥ 93.7 %) when using in the spray cooling. The results may provide the beneficial support for the potential application of spray with phase change suspension for the cooling of electronic devices.

High-Speed Fluorescence Imaging Corroborates Biological Data on the Influence of Different Nozzle Types on Cell Spray Viability and Formation

Treating severe dermal disruptions often presents significant challenges. Recent advancements have explored biological cell sprays as a promising treatment, but their success hinges on efficient cell delivery and complete wound coverage. This requires a good spray distribution with a small droplet size, high particle number, and ample surface coverage. The type of nozzle used with the spray device can impact these parameters. To evaluate the influence of different nozzles on spray characteristics, we compared air-assisted and unassisted nozzles. The unassisted nozzle displayed small particle size, high particle number, good overall coverage, high cell viability, preserved cell metabolic activity, and low cytotoxicity. Air-assisted nozzles did not perform well regarding cell viability and metabolic activity. Flow visualization analysis comparing two different unassisted nozzles using high-speed imaging (100 kHz frame rate) revealed a tulip-shaped spray pattern, indicating optimal spray distribution. High-speed imaging showed differences between the unassisted nozzles. One unassisted nozzle displayed a bi-modal distribution of the droplet diameter while the other unassisted nozzle displayed a mono-modal distribution. These findings demonstrate the critical role of nozzle selection in successful cell delivery. A high-quality, certified nozzle manufactured for human application omits the need for an air-assisted nozzle and provides a simple system to use with similar or better performance characteristics than those of an air-assisted system.

Development of spray‐dried oat milk powder with improved stability

AbstractBackground and ObjectivesOat milk is a plant‐based milk alternative and rich in various nutrients, however, the liquid product with a shorter shelf life limits its sales and consumption. This study is designed to develop an oat milk powder (OMP) using spray drying and improve the stability of reconstituted OMP by adding stabilizers.FindingsResults revealed that the optimal spray drying temperature was 160°C and the feed rate was 14 mL/min. The developed OMP showed higher bulk density compared to commercial soymilk powder. Furthermore, OMP maintained high contents of nutrients, including total phenol, β‐glucan, and various essential amino acids. The addition of stabilizers in OMP significantly decreased the turbidity and increased the pH stability, thermal stability, and freeze‐thaw stability of reconstituted OMP.ConclusionThe developed OMP product has abundant nutrients as well as stable physiochemical properties. Xanthan gum is the most effective stabilizer in improving the stability of reconstituted OMP across a wide range of pH and temperature.Significance and NoveltyThis study was the first to process oat milk into powder products and compare the effectiveness of different stabilizers in improving its stability. Our results suggest that OMP is a promising plant‐based beverage with stable physiochemical properties.

Classification of Plant Diseases by Image Processing for Optimal Spraying Purposes

Classification of Plant Diseases by Image Processing for Optimal Spraying Purposes