Spray Height Research Articles

Influence of flame stability on iron oxide nanoparticle growth during FSP

Flame stability during flame spray pyrolysis (FSP) remains an active topic of investigation due to its impact on synthesised particle attributes and purity. The unique feature of the burner investigated here is the ability to control flame stability over newly defined stability maps. The novelty of the current work lies in understanding the influence of these broad stability modes on nanoparticle growth during FSP and on the attributes of collected products. Several distinct flame configurations are selected for iron oxide nanoparticle synthesis, ranging from stable to highly unstable flames. The flame stability regimes are characterised by OH∗ chemiluminescence and broadband flame luminescence imaging. Stability is correlated with the coefficient of variation of flame luminescence (CV) and flame height with mean OH∗ chemiluminescence. Planar Mie scattering is then used to identify the effect of flame luminescence intermittency on spray atomisation and evaporation quality. For particle analysis, in-situ thermophoretic sampling is performed from 30 to 200 mm above the burner exit plane and analysed via transmission electron microscopy (TEM). Further ex-situ analysis is also performed on the bulk-collected product via high-resolution TEM, X-ray powder diffraction (XRD), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). It is demonstrated that flames with higher instability (CVmin ≥ 0.35) maintain increased spray heights (>26 %) and reduced flame heights (>79 %) compared to stable flames with the same precursor volume flowrate. This reduces the high-temperature particle residence time for primary particle growth and impacts subsequent agglomeration. For example, the mean diameter of gyration and primary particle diameter are found to vary by 44 % and 29 % depending on the flame regime, respectively. Ex-situ analysis also demonstrates that the dominant iron oxide phase produced is maghemite regardless of the stability regime. However, higher concentrations of organic impurities including methyl, methylene and carboxylate functional groups are found via ATR-FTIR with increased flame instability (CV).

Evaluation of unmanned aerial vehicle for effective spraying application in coconut plantations

Unmanned aerial vehicle (UAV) pesticide application in recent years owing to its importance such as time saving, reduction in human drudgery and also reduction in pesticides application rate. UAV has a great potential to address the problem involved in manual chemicals spraying in tall crops like coconut plantation where at present operation performed by manual climbing involves lots of drudgery and life risk. The current study aimed to understand the most influencing spraying parameters, such as spray height and spray time of the UAV sprayer on droplet characteristics such as spray droplet size, spray coverage and spray deposition at different layers (spindle, middle and bottom) of coconut tree canopy. The selected spray height (1, 2 and 3 m) and spray time (5, 8 and 11 s) significantly affects (p < 0.05) the droplet size (μm), spray coverage (%) and spray deposition (μl cm−2). In spray droplet size, the treatment T4, T5, T7 and T8 were recorded recommended droplet size of 50–400 μm in all layer of the coconut tree canopy. In spray coverage, the nearest value for recommended spray coverage of 10–20 % was observed for T1 and T5 treatment in all layer of the coconut tree canopy. The maximum penetration efficiency of 34.41 % had achieved at spray height of 2m and spray time of 8s (treatment T5). Based on performance of selected parameter, the spray height of 2 m and spray time of 8 s (treatment T5) was found best for spraying operation using UAV in coconut tree. The results showed the performance of the UAV offers best alternative for spraying operation on coconut tree and also this system will drastically reduce application time, labour requirement and improved the safety of coconut farmers.

Optimizing Vane Number for Enhanced Performance of Mist Blower Nozzle in Agricultural Spraying

The objective of this study is to optimize the number of vanes equipped in the propeller of a mist blower's nozzle. Performance tests were conducted on the approved sprayer test bed, also known as a patternator, to measure several parameters, including effective spraying discharge, effective spraying width, spraying angle, effective spraying height, effective spraying range, droplet diameter, and droplet density. The vane number was optimized using the weighting method. The results indicate that increasing the number of vanes used is directly correlated with higher values of effective spraying width (ESW), spraying angle, effective spraying range (ESR), and droplet density. Conversely, it is inversely correlated with the value of effective spraying discharge (ESD), effective spraying height (ESH), and droplet diameter. The vane number was optimized using the weighting method. The most effective results in the mist blower performance test are achieved by using 12 vanes. This configuration produces droplets with a diameter of 195.44 ±9.68 μm and a density of 320 ± 17.44 droplets/cm2. The mist blower also has ESW of 136 ± 1.73 cm, ESH of 68.14 ± 4.19 cm, ESD of 4.41 ± 0.14 L/min, and ESR of 5.76 ± 0.04 m. Keywords: Agricultural spraying, Mist blower, Nozzle optimization, Performance evaluation, Vane number.

Assessment of sensor-based automatic smart watering unit for paddy nurseries under Indian perspective

A sensor-based automatic watering unit was developed to irrigate the paddy seedling trays. The watering unit comprised six flat spray nozzles with a direct current (DC) water pump and flow sensor, and these were kept at the top of the conveyor frame, which was actuated by a DC water pump with a solenoid valve to drop the water in trays. The actuation of the DC solenoid valve was controlled by a limit switch fitted to the conveyor frame, which sensed the moving trays on the conveyor. The performance of the developed unit was evaluated, and process optimization was performed using the Inscribed Central Composite Design in Response Surface Methodology. The effect of main operating parameters- chain conveyor speed (0.123, 0.196, and 0.27 m/s), spray operating pressure (1.5, 3.0, and 4.5 kg/cm2), and spray height (10,30 and 50 cm) on the performance of the sensor-based automatic watering unit was studied in terms of the amount of water spray requirement and coefficient of water spray uniformity in trays. The responses of the unit at its optimal parameter operation (spray operating pressure 4.5 kg/cm2, spray height 10 cm, and chain conveyor speed 0.14 m/s) were found to be 1.31 L/tray as the amount of water spray requirement and 92.41 % as the coefficient of water spray uniformity of the unit. Hence, it can be an efficient substitute with significantly less power consumption 41 W with a higher working capacity of 780 trays/h for watering into the paddy tray nursery. The developed sensor-based automatic smart watering unit saves irrigation water per square area of 68.90 %, 76.13 %, and 82.31 % compared to existing drip, sprinkler, and flood irrigation methods in mat-type paddy nurseries. The developed sensor-based automatic smart watering unit saves the watering cost INR 11,567.16 (140.02 USD) per hectare, reducing cost by 63.7 % compared to manual watering in the mat-type nursery preparation. Thus, an automatic smart watering unit in a paddy tray nursery offers consistent and uniform watering from an Indian perspective, promoting uniform germination, crop growth, and establishment. It conserves water by ensuring the right amount of water is applied at the right time, avoiding overwatering or under-watering.

Effects of different spray parameters of plant protection UAV on the deposition characteristics of droplets in apple trees

Plant protection UAVs have developed rapidly as a new type of orchard pesticide application equipment. This study was conducted to explore the influence of plant protection UAVs' operation parameters on the properties of droplet deposition. The DJI T30 plant protection UAV was used to affect the influences of spray volume (60 L/ha and 90 L/ha), spray height (2m and 2.5m), with or without an adjuvant and spray patterns (Regular pattern and Orchard pattern) on characteristics of droplet deposition. The test results showed that the interaction of multiple factors has no significant difference in most droplet deposition on various layers of fruit trees. The deposition characteristics of droplets were improved at a spray height of 2 m and a spray volume of 90 L/ha in the presence of adjuvants. In the orchard spray pattern, the penetration of droplet deposition is improved, but the impact on droplet density and coverage is different. Overall, the orchard spraying pattern can achieve better coverage, while the droplet density is the opposite. The spray performance is closely related to the spray volume, with or without an adjuvant, spray pattern, and spray height. The research results provide a theoretical basis for selecting appropriate operating parameters and spray patterns for plant protection UAVs in apple orchards.

Optimization of Spray Characteristics of Full Cone Nozzles Used in Pesticide Application Using the Taguchi Method

The present study aims to reduce the amount of pesticide that can be released into environment, soil, air, and water by minimizing the type of nozzle and the use of excess pesticides by making use of the Taguchi method. For this purpose, studies were carried out to determine the spray characteristics of the pesticide. The sodium fluorescein was used in the experiments. In this study, the effects of the nozzle-to-surface distance (spray height), spray pressure, nozzle orifice diameter, and nozzle position angle on the droplet diameter and flow characteristics were investigated using the Taguchi method. The mean diameter values were determined first. Then, the volumetric median diameter (VMD) was considered as performance parameter and L9(34) orthogonal sequence was chosen as the experimental plan for four parameters that were determined. Calculating the VMD considered as the performance characteristics, optimum results were obtained using 6 bar spray pressure, 100 mm spray height, 30o nozzle position angle, and 1.10 mm nozzle orifice diameter. The VMD values were calculated using the image processing method and the effects of the parameters on the droplet diameter were interpreted using charts.

Enhanced performance of thermoelectric generation system by increasing temperature difference using spray cooling

Thermoelectric generation system (TEGS) can directly convert the waste heat to electricity in practice. The power generation is highly impacted by the temperature difference between the hot and cold ends. To significantly improve the temperature difference, various cooling technologies have been applied to TEGS. However, there is still room to further increase the power generation efficiency of TEGS by enhancing the cooling performance. Herein, spray cooling was introduced to the TEGS and influencing factors were investigated. The experimental study demonstrates that, upon the spray cooling, the cold-end temperature can be dramatically reduced up to 27 °C. Further, the output performance of the TEGS was substantially increased by optimizing spray heights, flow rates and heat source temperatures, etc. For example, for the spray height of 3 cm, the TEGS achieves a maximum output voltage because the thermoelectric generation module (TGM) is completely covered by the spray area in this study. Moreover, the temperature difference between cold/hot ends and voltage of the TEGS are further increased to 55 °C and 1.39 V at a flow rate of 100 L/min. On the other hand, increasing the heat source temperature (hot end temperature) can also strongly improve the output performance of the TEGS. Particularly, compared to passive air cooling, spray cooling can enable the TEGS to significantly increase its output voltage and current by 17 and 27 times, respectively. Finally, this study would potentially provide a new cooling strategy to strongly enhance the output performance of TEGS.

Analysis of Avgas Fuel Spraying Schemes Using the ANSYS Application Approach

Avgas fuel consumption on Cessna trainer aircraft is very high. However, there has been little research regarding spray impacts in Cessna aircraft engines. The phenomenon of avgas spray colliding with the cylinder wall may occur during fuel injection, resulting in a changed spray radius and height, which will affect the mixing of fuel and air. In several aspects, this affects engine performance and exhaust emissions on Cessna aircraft. This research aims to determine and study the phenomenon of spray impact on avgas-fueled aircraft engines. The fuel spray in the study occurred in the combustion chamber using pressure from a fuel hand pump whose pressure was supplied from a compressor with a pressure adjusted to the original pressure on the aircraft, namely 2 Bar (30 Psi). The experiments in this research used a high-speed camera system to study the phenomenon of avgas spray on walls to get better spray distribution. The results of this research were processed using the CFD application. The result of this research is that the greater the pressure, the more concentrated the resulting jet will be on the jet wall so that the atomization of the fuel jet will be dispersed. When the burst occurs, a change of 3.80e+00 occurs compared to other burst pressures.

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.

Experimental Study on Spray Uniformity

This study involves simulating rainfall conditions to analyze rainfall intensity and spray uniformity, conducting environmental experimental research. Using numerical analysis methods, water mass fraction cloud maps under different flow conditions were obtained to determine the relationship between uniformity, water flow rate, and water mass fraction. Based on the simulation results in accordance with relevant standards, two methods for measuring rainfall uniformity are selected based on water pressure, nozzle type, and spray height as basic parameters for setting measurement points, and rainfall environmental simulation experiments are conducted. The theoretical analysis provides a clearer representation of water quality distribution than steady-state analysis; water mass fraction is proportional to water flow rate, while uniformity is independent of water flow rate. Through comprehensive comparison of uniformity data for different nozzle models under varying water pressure and height conditions, recommendations are made for the placement of rain gauges in rainfall environmental experiments. Adjusting various test environment parameters can provide references for the test lab to accurately select test equipment, parameter measurement, and evaluation; the water mist environment generated during rainfall is simulated through spray towers, and the numerical uniformity test results of the water mist environment are consistent with the requirements, providing theoretical data support for developing more authoritative test methods for equipment sprinkler tests and ultra-fine water mist environment simulation in the future.

Insights on droplet drift and effective utilization of pesticide in “Third Pole”：Qinghai-Tibet Plateau of China

Crop protection pesticide spraying aims to greatly improve the utilization rate of pesticides. Controlling pesticides deposition requires a thorough understanding of the spatial behaviour of spray droplets.The Qinghai-Tibet Plateau, which is the headwaters of three largest water resources (Yangtze, Yellow and Lancang) in China, has exceptionally unique climatic characteristics. The goal is to reduce the amount of pesticides entering water resources. The wind tunnel experiment was used to validate the discrete phase method for tracking the trajectories. Cooperation between the smaller and larger droplets (greater than 150 μm) in the dense area around the nozzle can undoubtedly enhance the initial dispersion of droplet sizes. Droplet coalescence, which lowers the proportion of readily dispersed droplets, can greatly boost droplet deposition onto the target location.The crucial drift height is presented and clarified when droplets gradually disperse by identifying the descending length at which efficiency of mass transit starts towards decrease off quickly. The pesticide transport efficiency will not be enhanced by reducing the initial relative spread of droplets if the actual spray height surpasses the crucial drift height, and may even worsen drift loss. The temperature and relative humidity of the air have a greater influence on the evaporation losses of droplets smaller than 150 μm. In addition to providing information about pesticide spraying, the results of studies on droplet drift behaviors also suggest a method for controlling drift.

An Original UV Adhesive Watermelon Grafting Method, the Grafting Device, and Experimental Verification

This study is aimed at traditional vegetable grafting using a large number of plastic clips, which cannot be recycled in time and cause serious pollution within the planting environment. This paper proposes a new grafting method based on a UV adhesive instead of plastic clips. First of all, a UV adhesive spray grafting device was designed. The structure includes seedling adsorption positioning mechanisms, a butt joint mechanism, a handling mechanism, a spray valve, a UV curing lamp, etc., to facilitate the adhesive spraying. For the rootstock and scion, a horizontal, lateral seedling and negative pressure adsorption and positioning method is adopted, with fluid dynamics simulation of the diameter and quantity of the adsorption holes in the rootstock adsorption mechanism carried out using Fluent 2022 R1 software and completion of the optimization of the parameters of the adsorption and positioning mechanism. The fluid volume method is used to simulate the adsorption and positioning mechanism. For optimization, the volume of fluid method (VOF) and the discrete particle method (DPM) are used in a coupled simulation of the UV adhesive spraying process, and the value range of the spraying influencing factors is determined: the selected glue pressure, atomization pressure, and spraying height for three-factor, three-level orthogonal simulation. A grafting test is also verification, deriving the significance ranking of their impact on the success rate of the grafting: atomization pressure &gt; spraying height &gt; glue pressure. Under the condition of a 0.25 Mpa atomization pressure, a 0.15 Mpa glue supply pressure, and a 10 mm spraying height, the grafting success rate for watermelon was 100%, the effective spraying rate was 83.03%, the healing success rate was 94.5%, and the length of the film was 7.86 mm. The results of the study can provide a research basis for the research and development of new types of spraying and grafting robot technology.

The Experiment and Simulation on Impact Characteristics of AVGAS Spray Based on Impact Phenomenon

Avition gasoline (avgas) is one of the fuels used for combustion of piston-type aircraft engines and uses ignition in the form of spark plugs or internal combustion engines. In recent years, the use of avgas fuel itself is very high used in high- wing light aircraft engines, namely Cessna. avgas spray phenomenon that collides with the cylinder wall may occur during fuel injection, so it will produce a changed radius and spray height, which will affect the mixing of fuel and air, later engine performance and exhaust emissions will also be affected. Therefore, it is important to know and study the spray impact phenomenon in avgas-fueled aircraft engines. This research is a spray experiment with a specified pressure and sprayed on the combustion chamber wall so that the results of the image can be studied coupled with data from experimental research, it can make research from computational fluid dynamics (CFD) simulations, providing valuable insights for future research in this field.

Experimental study on heat-transfer characteristics of spray cooling for microchannel radiators

Spray cooling is an emerging and promising thermal-management solution with a wide range of applications. However, its application in engineering vehicles remains in the formative stage. In this study, an innovative spray-cooling system for engineering vehicles was proposed. The study, using thermocouples and visualisation methods, focused on how factors such as the spray angle, height, volume flow, nozzle aperture, and arrangement impact the uniformity of the surface temperature and heat-transfer enhancement. Optimal cooling was achieved using a spray angle of 60°, height of 90 mm, and flow rate of 500 l/h. Moreover, a nozzle aperture of 1.6 mm demonstrated superior efficiency in energy use and cooling. Higher temperature differentials (90–140 °C) enhanced the heat transfer but led to a 332.81 % increase in the non-uniformity of the surface temperature. Further, the study compared the spray-cooling efficiency between alumina nanofluids and deionised water. Alumina nanofluids with a 0.7 % mass fraction achieved a maximum heat-transfer coefficient of 450.6 W/(m2·K), 15.48 % higher than that of deionised water. Moreover, based on the experimental results, an empirical formula for enhanced heat transfer using spray cooling in construction machinery was developed, providing a valuable reference for guiding engineering practice. The proposed spray-cooling method, which exhibited a two- to three-time improvement over traditional air-cooled systems, holds considerable promise in the field of engineering vehicle applications.

Spray Cooling Heat Transfer of a Two-Fluid Spray Atomizer

Abstract The paper presents an experimental study on the droplet size and velocity, as well as temperature distribution, of a two-fluid atomizer (dj=1.6mm; spray nozzle exit diameter) through optical non-intrusive interferometric particle image (IPI) and particle image velocimetry (PIV) measurements with five different air liquid ratios (Rs) at three spray heights with three target-plate initial temperatures. Cold flow visualization was made for the spray height of 50 mm at 25oC. The Saunter-mean diameter (d32) was measured at the target temperature of 25°C without heating and found to be in the range of 34.22µm to 42.62µm in terms of a correlation with We(dj) Re(dj). The measured impact velocity at the spray height of 50 mm was of 10m/s to 30m/s with three different initial target temperatures. It was found that the impact velocity displayed a strong function of the initial temperature. Furthermore, both the cooling curve and transient boiling curve were obtained with the identified cooling/boiling parameters of the cooling rate, critical heat flux (CHF), Leidenfrost temperature (LFT), as well as the onset of nucleate boiling (ONB). The best cooling performance was found at R=0.242 for a spray height of 50 mm with the corresponding cooling rate of -19.1°/s, CHF of 486 W/cm2, and heat transfer coefficient (HTC) of 2.85 W/cm2K.

Simulated drift of 2,4-D and dicamba in pecan (&lt;i&gt;Carya illinoinensis&lt;/i&gt; K. Koch) and olive trees (&lt;i&gt;Olea europaea&lt;/i&gt; L.)

The cultivation of pecan (Carya illinoinensis K. Koch) and olive trees (Olea europaea L.) near pasture and grain cultivation areas in southern Brazil has caused herbicide drift problems. Therefore, the objective of this study was to evaluate the phytotoxic effects of herbicides 2,4-D and dicamba on the growth of pecan and olive tree seedlings. A total of 8 underdoses were used, as follows: 0, 1.56, 3.125, 6.25, 12.0, 25.0, 50.0, and 100% of the recommended doses of herbicides 2,4-D (670 g a.e ha−1) and dicamba (720 g a.e ha−1) for burndown. The applications were carried out in 80 cm-high seedlings with the aid of a CO2 pressurized sprayer with a spray solution volume of 150 L. ha−1. The analyzed variables were phytotoxicity at 7, 14, 21, 30 and 60 days after spray (DAA) and plant height and stem diameter at 30 and 60 DAA. The drift of hormonal herbicides caused damage to the growth of pecan and olive trees, decreasing their stem diameter and height, with the herbicide dicamba showing the greatest damage. In addition, doses above 12.5% of both herbicides resulted in phytotoxicity levels greater than 60%, and doses of 50 and 100% were responsible for leaf senescence.

Numerical Investigations of the Cooling Performance of an R410A Closed-Loop Spray Cooling System

To investigate the spray cooling characteristics and the impact of spray parameters such as chamber pressure, spray height, and spray tilt angle on heat transfer efficiency, a mathematical model based on the Eulerian–Lagrangian frame was established for an R410A closed-loop spray cooling system. The results revealed that the spray pattern is conical, with the center velocity significantly higher than the edge velocity. The temperature distribution of the cooling surface and liquid film height both exhibit a “W” shape, and the surface temperature is lower where the liquid film is thin. There is an optimal liquid film height of approximately 5 μm, at which the cooling surface temperature is the lowest. The surface temperature increases with an increase in the spray chamber pressure. Considering average cooling surface temperature, the optimal tilt angle is 40° with an average surface temperature of 330.1 K. When considering wall temperature and wall heat transfer coefficient uniformity, however, the optimal tilt angle is 10°, leading to the average surface temperature of 332.6 K. When increasing the optimal spray height to 70 mm, the average surface temperature is 313.4 K.

An intelligent spraying system for weeds in wheat fields based on a dynamic model of droplets impacting wheat leaves.

Targeted herbicide application refers to precise application of herbicides in weed-infested areas according to the location and density of farmland weeds. At present, targeted herbicide application in wheat fields generally faces problems including the low herbicide adhesion rate, leading to omission and excessive loss of herbicides. To solve these problems, changes in the impact force of herbicide and the weed leaves in the operation process of a spraying system were studied from the interaction between weeds and herbicides applied. A dynamic model of weed leaves was established. On this basis, the research indicated that the herbicide adhesion rate is highest under spraying pressure of 0.4 MPa and flow rate of 0.011 kg/s when the spray height is 300 mm. To study the dynamic deformation of weed leaves and the distribution of liquid herbicides in the external flow field under weed-herbicide interaction, a dynamic simulation model of herbicide application was built using the finite element method. The results show that when the spray height is 300 mm, the maximum weed leaf deformation index (LDI) is 0.43 and the velocity in the external flow field is 0 m/s under spraying pressure of 0.4 MPa and flow rate of 0.011 kg/s. This finding indicates that the herbicide is not splashed elsewhere and the turbulence intensity in the weed area is 2%, implying steady flow of the herbicide, most of which can be retained on weed leaves. Field test results of application quality of the herbicide show that the maximum LDI is 0.41 and the coverage of the herbicide in the sheltered area below the leaves is 19.02% when the spraying pressure is 0.4 MPa, flow rate is 0.011 kg/s, and spray height is 300 mm. This solves the problem of a low rate of utilization of herbicides because the herbicide passes through weed plants, and achieves the precision herbicide application in wheat fields.

Optimizing spray cooling systems: A comprehensive study on influential parameters and their effects on heat transfer under varied heat flux conditions

This research explores the heat transfer characteristics of spray cooling under heat flux conditions ranging from 10 to 200 W/cm2 through numerical simulations. We examined the effects of spray height, spray pressure, surface tension, contact angle, system pressure, and gravity on spray cooling efficiency, to optimize spray cooling systems. Furthermore, we validated the simulation results through experiments and found a good agreement between the two. Key findings include a consistent increase in the heat transfer coefficient with rising heat flux. Under specific heat flux density, increased spray pressure leads to a gradual decline in wall temperature and improved wall temperature uniformity, but the reduction rate slows as pressure continues to increase. Lower spray heights can improve cooling efficiency, but may reduce temperature uniformity. Additionally, heat transfer performance in the two-phase zone improves with higher surfactant (Tween 20) concentration, with a 75ppm solution reducing cooling wall temperatures by 7.4 K compared to pure water. Spray processes at 10 kPa and 50 kPa result in lower wall temperatures before entering the two-phase zone compared to atmospheric pressure, improving cooling efficiency and temperature uniformity. Finally, differences in spray cooling effects under varying gravities manifest primarily during the two-phase heat exchange stage, with the temperature difference widening with increasing heat flux density. These insights offer valuable guidance for spray cooling applications in electronic thermal management.

Factors influencing subcanopy leaf and stolon exposure and associated absorption and translocation of herbicides in semidormant zoysiagrass

AbstractTurfgrass managers are concerned about zoysiagrass (Zoysia japonica Steud.) injury from nonselective herbicide treatment during winter dormancy. Research was conducted to assess factors affecting spray penetration into semidormant ‘Meyer’ zoysiagrass canopies and to evaluate absorption and translocation of [14C]glyphosate and [14C]glufosinate into green leaves and subtending stolons. Absorption of [14C]glyphosate and [14C]glufosinate was up to four times greater in stolons than in leaves. Zoysiagrass leaves treated with [14C]glufosinate had more rapid 14C absorption than those treated with [14C]glyphosate. More 14C translocated out of the treated area following [14C]glyphosate treatment compared with [14C]glufosinate and moved more readily from stolon to leaves than from leaves to stolon. When extended-range, flat-fan spray tips (XR) were positioned 61 cm above zoysiagrass, 73% and 11% of recovered colorant was extracted from dormant vegetation in the upper and lower canopy levels. Turbo TeeJet® spray tips (TTI) deposited fewer droplets into the upper canopy and more droplets into the middle and lower canopy regardless of position above the turf surface. Increasing pressure from 103 to 414 kPa increased droplet velocities from XR and TTI nozzles and decreased droplet diameters of XR nozzles. Droplet diameters were also substantially increased when using TTI nozzles compared with XR nozzles. Droplet diameter and associated mass were more determinant of turfgrass canopy penetration than droplet velocity. At 60 L ha−1 of carrier volume, 23% of colorant reached the lower canopy level, and this quantity increased by 2.3% per additional 100 L ha−1. When carrier volume was reduced from 584 to 60 L ha−1, 48% less colorant was delivered to the lower canopy level. Given that subcanopy stolons are always present and absorb more glyphosate and glufosinate than leaves, practices such as avoiding induction-type nozzles, raising spray height, and reducing spray volume can reduce herbicide delivery and potential injury to semidormant zoysiagrass.