Increasing Air Velocity Research Articles

Research and numerical assessment of design and construction errors in the swimming pool facility structures

Swimming pools are characterized by high humidity, high temperature, an aggressive environment caused by disinfection processes, high energy consumption, and extensive technical infrastructure. As a result, these facilities are at high risk of damage, including structural damage, which can have catastrophic consequences in extreme cases. Adequate ventilation plays a critical role in natatoria. The technical condition of swimming pool facilities should be regularly inspected to ensure that they are safe for the public. Various techniques can be used for this purpose. In the present study, a numerical analysis of ventilation performance and an assessment of the risks associated with design and construction errors in the ventilation system were conducted in a swimming pool building with a volume of 116,280.7 m3 and a surface area of 20,188.6 m2 in north-eastern Poland. Two scenarios were analyzed: the performance of the originally designed ventilation system and the performance of the ventilation system installed in the examined facility. The analyses were conducted with the use of computational fluid dynamics (CFD) tools in the FloVent program. Air distribution was determined by measuring ventilation parameters and conducting smoke tests in analyzed natatorium, and the obtained data were consistent with the results of the numerical analysis. The analyzed scenarios were compared to identify the risks associated with inadequate ventilation in swimming pools. A significant decrease in air supply led to local increases in air velocity and worsened thermal comfort parameters in the real-world facility. In addition, the decrease in air supply induced changes in air distribution and prevented air streams from reaching all parts of the natatorium. Some areas were inadequately ventilated, and condensed water vapor settled on the building’s glass facade and the roof, posing a direct threat to structural elements. The results of the numerical analysis were congruent with on-site measurements, which indicates that CFD tools are highly useful for assessing ventilation systems in swimming pools. These tools can be used to analyze ventilation performance and optimize the proposed solutions already at the design stage. The applied tools enable designers to eliminate construction errors and optimize a building’s structural safety, performance, and energy efficiency.

Exploring water desalination in an arid climate: An experimental and numerical analysis of a compact solar chimney

Water scarcity has been proclaimed one of the biggest challenges in the 21st century. This study developed a novel compact solar desalination system based on a chamber (basin) and a chimney where water is evaporated and condensed, respectively. A transient numerical model based on fundamental principles was developed, which uses actual weather conditions to predict the performance of the solar tower desalination system. It was validated with the obtained experimental hourly water production and temperatures in the chimney in a city with a desert climate. A detailed thermal analysis with contours of temperature and mass fraction and streamlines is presented. Also, profiles of water evaporated/condensed are exhibited. Finally, the overall and condensation efficiencies were computed. The transient computational model could replicate experimental hourly water production and temperatures in the chimney with good agreement. The system in the actual state could produce up to 6052 mL of clean water under summer weather conditions. The increase in air velocity to 3.5 m/s improved clean water production by 19.82 % and condensation efficiency by 18.38 %.

Numerical analysis of the divergent solar chimney power plant with a novel arc and fillet radius at the chimney base region

Solar chimney power plant (SCPP) is an ingenius concept of harnessing the solar energy for the electrical power generation, provided their efficiency is enhanced significantly. The present work focuses on the improvement of the power generation and efficiency of the plant. A finite volume CFD code is developed in FORTRAN to deal with the axisymmetric domain of the SCPP. The effect of chimney divergence angle, collector height and a novel arc and fillet radius at the chimney base is studied. For the study, an SCPP with 3 m collector diameter and 3 m chimney height with 0.05 m radius of the chimney is considered. The height of the collector is optimised and found to be 0.04 m. Diverging the chimney results in more updraft which leads to more pressure difference and increased air velocity. Also, after an optimum divergent angle, further increasing the divergence angle results in a severe reverse flow at the chimney outlet. It is observed that 2o divergent chimney is optimum which enhances air velocity by 59% and produces 290% more power than the conventional SCPP. Further improvement in the power is noticed by using the arc and fillet radii at the chimney bottom. After extensive analysis of the flow parameters, an optimum value of arc and fillet radii is proposed to be 0.1 m and 0.01 m respectively. It is noticed that for this optimum case, maximum available power is about 122% higher than the 2o divergent chimney case without any arc or fillet. The proposed design has produced an overall increment of 770% in the maximum available power of the plant and about 154% increment in the mass flow rate compared to the base case. The proposed design also enhances the collector and chimney efficiencies by about 49% and 76% respectively.

An investigation on shell-side thermal–hydraulic performance of helically coiled tube heat exchanger for deep underground space

Helically coiled tube heat exchanger (HCHE) was extensively used to enhance the thermal environment of deep underground space. The inefficiency of heat transfer in the mine cooling system results in increased operational energy consumption. To enhance heat utilization, this study examines the impact of air temperature, air velocity, coil diameter, pitch, and elliptical tube aspect ratio on the shell-side thermal performance of HCHE through experimental and numerical analysis. The performance evaluation criterion (PEC) and field synergy are introduced to provide a comprehensive assessment of performance. Results suggest that the air velocity can more significantly affect the thermal performance of HCHE than air temperature. Augmenting the coil diameter from 30 − 40 mm and coil pitch from 7.5 − 9.0 mm led to an increase in the Nu number by 16.5 % and 6.7 %, as well as an increase in friction factor f by 575.2 % and 147.1 %, while a reduction in PEC by 38.4 % and 21.1 % when the air velocity is 5 m/s, respectively. For the helically coiled elliptical-tube heat exchanger (HCHE-E), the thermal performance is significantly dependent on the long axis's direction and its aspect ratio. When the air velocity is 3 m/s, the increase in aspect ratio from 1.0 to 1.8 resulted in a decrease and increase in Nu by 14.7 % and 14.6 %, an increase and decrease in PEC by 24.5 % and 28.4 %, as well as a reduction and increase in f by 31.5 % and 48.1 % for the long axle in the horizontal and vertical directions, respectively. The PEC for HCHE is not significantly dependent on the air velocity. The increase in air velocity can result in the augment in PEC of HCHE-E regardless of long axis's direction. The variation of synergy angle is consistent with the change of Nu. These findings offer valuable insights for optimizing the design parameters of HCHE in deep underground spaces.

A study into how thickness, infrared intensity, and airflow affect drying kinetics, modeling, activation energy, and quality attributes of apple slices using infrared dryer.

Drying is a widely recognized process that reduces the need for storage and shipping weight, keeps free water out of the product, and prolongs its shelf life. An infrared dryer was designed to dry apples under different drying conditions. Apple slices of 6-, 4-, and 2-mm thicknesses were dried at intensities 0.130, 0.225, and 0.341W/cm2 and airflow 1.0, 0.5, and 1.5m/s. The dehydrating period was prolonged with higher airflow and shortened with higher infrared intensity (IR). The shortest dehydrating period was verified by 190min at 0.341W/cm2, 0.5m/s under 2mm thickness. Increasing the sample thickness from 2 to 4 mm and then to 6mm resulted in an 84% and 192% increase in drying time, respectively. Dehydrated apples had water activity values ranging from 0.30 to 0.40. The shrinkage ratio increased with an increase in infrared radiation intensity. However, it decreased with an increase in air velocity, while the rehydration ratio decreased with an increase in radiation intensity and increased with an increase in air velocity. Regarding total color change, apple slice thickness was a major factor. The effective diffusivities varied between 2.6 and 9.0 𝗑10-10 m2/s under different drying conditions. The dehydrating curves of apples were best described by the model developed by Midilli etal.

Design of a hemispherical shell shaped natural ventilation temperature observation instrument.

Atmospheric temperature is fundamental information for various industries, such as production, life, and scientific research. The temperature error induced by the solar rays can reach 1 °C or even higher. A hemispherical shell-shaped atmospheric temperature measuring instrument that can reduce heat pollution and increase air velocity was designed. First, the instrument was optimized using computational fluid dynamics (CFD) software packages. Then, the CFD software packages were employed to quantify the temperature errors of the instrument with varying situations. A neural network model was employed to develop a temperature error correction model that can be targeted for multi-variable changes. This model provides accurate correction data when the influencing factors change continuously. Finally, field experiments were performed. The experimental data analysis indicates that the mean temperature error and the maximum error of the instrument before correction are 0.08 and 0.25 °C, respectively. The root mean square error, the mean absolute error, and the correlation coefficient between measured temperature errors from experiments and corrected temperature errors from the correction model are 0.099, 0.016, and 0.952 °C, respectively. By utilizing a temperature error correction model, the measuring error of the instrument can be minimized to a range between -0.05 and 0.04 °C. Consequently, the instrument is anticipated to enhance temperature measurement accuracy to ∼0.1 °C.

Study on flow characteristics of vertical pneumatic conveying of stiff shotcrete materials based on CFD-DEM

In view of the vertical pneumatic transportation process of stiff shotcrete materials (SSM), the method of CFD-DEM coupling numerical simulation was used to analyze the flow characteristics of the SSM. In this aspect, the flow characteristics of SSM transported by vertical pipe pneumatically under different solid-gas ratios were studied. Among them, the accuracy of the simulation results was verified through SSM particle parameter calibration and field testing. The research results show that during the process of vertical pneumatic transportation, full pipe flow, annular flow, and suspended flow can be clearly observed in the pipe. The cross-sectional particle volume fraction increases as the feeding rate increases, and the conveying stability becomes worse. As the air velocity increases, and the conveying stability becomes better. This study can provide support for research on vertical pneumatic conveying, thereby effectively reducing energy loss during the process of spraying

The Effect of the Periodic Drying Method on the Drying Time of Hazelnuts and Energy Utilization.

Hazelnut is a shelled fruit that is stored by drying and used as a snack or in industry. Since the hazelnut drying process is energy-intensive, there is a need for drying methods that will reduce the energy cost without lengthening the drying time. In this study, the effects of periodic drying of hazelnuts' energy recovery, oil, and protein content, as well as mass losses, were studied. Fresh Tombul hazelnuts (Corylus avellana L.) with a diameter of Ø 15-16 mm were dried in a tunnel dryer over 16 different periods by adjusting the drying time inside and waiting time outside the oven until the moisture content reached 6%. Drying experiments were carried out at 45 °C and three different air velocities. The increase in air velocity resulted in a reduction in the periodic drying time between 10% and 36%. The optimum drying in terms of drying time and energy utilization was realized at 0.5 m/s air velocity, with a 1.5 h working time and 0.5 h waiting time. During this period, drying time increased by 19% and energy utilization was 69%. For periodic drying, the increase in oven working time causes a decrease in energy utilization, while the increase in waiting time causes an increase in energy utilization and drying time. Periodic drying had no negative effect on hazelnut oil and protein content. Periodic drying is a suitable option for saving energy during hazelnut drying.

Heat Convection in a Channel-Opened Cavity with Two Heated Sources and Baffle

This study employs COMSOL software v 5.6 to investigate a novel approach to heat transfer via mixed convection in an open hollow structure with an unheated 90° baffle elbow. Two 20 W heat sources are strategically positioned on the cavity’s bottom and right-angled wall for this research. Notably, the orientation of the baffle perpendicular to the airflow is used to direct external, unrestricted flow into the square cavity. The research investigates a range of air velocities (0.1, 0.5, 1.0, and 1.5 m/s) and the intricate interaction between input air velocity, dual heated sources, and the presence of a right-angle baffle on critical thermodynamic variables, such as temperature distribution, isotherms, pressure variation, velocity profile, air density, and both local and mean Nusselt numbers. Validation of the applicable computational method is achieved by comparing it to two previous studies. Significant findings from numerical simulations indicate that the highest velocity profile is in the centre of the channel (2.3–2.68 m/s at an inflow velocity of 1.5 m/s), while the lowest profile is observed along the channel wall, with a notable disruption near the inlet caused by increased shear forces. The cavity neck temperature ranges from 380 to 640 K, with inflow air velocities varying from 0.1 to 1.5 m/s (Re is 812 to 12,182), respectively. In addition, the pressure fluctuates at the channel-cavity junction, decreasing steadily along the channel length and reaching a maximum at the intake, where the cavity neck pressure varies from 0.01 to 2.5 Pa with inflow air velocities changing from 0.1 to 1.5 m/s, respectively. The mean Nusselt number exhibits an upward trend as air velocity upon entry increases. The mean Nusselt number reaches up to 1500 when the entry air velocity reaches 1.5 m/s. Due to recirculation patterns, the presence of the 90° unheated baffle produces a remarkable cooling effect. The study establishes a direct correlation between input air velocity and internal temperature distribution, indicating that as air velocity increases, heat dissipation improves. This research advances our understanding of convective heat transfer phenomena in complex geometries and provides insights for optimising thermal management strategies for a variety of engineering applications.

The effect of increased air velocity on respirations rate and resting behavior in gestating sows on moderately warm summer days

Heat stress is a challenge for farm animals and animal production, particularly in warmer regions of the world. In pig production, the consequences of heat stress are the adverse effects on animal welfare including behavioral alterations, increased respiration rate, body temperature and mortality and reduced feed intake, milk production and piglet growth rate. The objective of the present study was to investigate the effect of increased air velocity through wall air inlets directed towards the resting area on respiration rate and resting behavior of gestating sows under commercial conditions.The gestating sows were loose housed and chill inlets (including adjustable guiding plates to direct the incoming air in a downward direction) directing air towards the resting area were mounted in one of two resting areas within each pen. The purpose of the latter was to investigate whether the sows preferred to lie in the area with increased air speed. Compared to normal inlets (control) the chill inlets increased the average air velocity from 0.19 to 0.45 m/s (measured 0.4 m above the floor). Respiration rate was recorded and the chill inlets significantly reduced the respiration rate (P < 0.0001). Within the three temperature intervals, 24.4–27.0, 27.1–28.2 and 28.0–32.2 ⁰C, the reduction was 4.2, 6.2 and 7.6 bpm (beats per minute) respectively.There was no difference in percentage of sows resting in the lying areas with activated vs. inactivated inlets.

Filtration of dust particulates with a granular bed filter in a novel coupled separator

In this study, the filtration performance of the built-in granular bed in a cyclone-granular bed coupled separator is investigated. Cyclone is used to recover catalyst particles from the regenerated flue gas in the Fluid catalytic cracking by centrifugal force. While the granular bed captures fine dust particles smaller than 10 μm. Catalyst loss problem can be addressed by coupling different separation mechanisms in the coupled separator. To clarify the separation process, the necessity to elucidate the filtration performance is shown The investigation has been performed for the velocity distribution measuring and the bed dust deposition, and the filtration efficiency in the coupled separator under varying operating parameters. Experimental results indicate that the radial velocity component is a main influencing factor on the granular bed filtration efficiency. The outer-layer bed collector particles exhibit superior dust collection capabilities. Based on the intrusive dust sampling, a diagram is presented to clearly illustrate the primary mechanisms that govern dust movement in the bed. Furthermore, two parameters named by the local filtration efficiency (LFE) and the filtration efficiency across radius (FEAR) are proposed for analyzing the granular bed filter performance. The LFE exhibits a declining trend as the inlet air velocity increases. The dust size distribution analysis highlights the capacity of the bed to capture fine dust particles (<5 μm) which tended to accumulate at the inner layer. The FEAR, ranging from 91 % to 97 %, offers a comprehensive assessment of the coupled separator performance and structural optimization.

Determining the effective diffusivity coefficient and activation energy in thin-layer drying of Haj Kazemi peach slices and modeling drying kinetics using ANFIS

Abstract This study investigated the moisture changes in Haj Kazemi peach slices during drying in a thin-layer dryer at five temperature levels (40, 50, 60, 70, and 80°C), three levels of inlet air velocity (1, 1.5, and 2 m/s), and three slice thicknesses (2, 4, and 6 mm). The relative moisture content during drying was calculated, and an adaptive neuro fuzzy inference system (ANFIS) was used to predict the drying process of peach slices. The results indicated that slice thickness had a greater impact on drying time than air velocity. Moreover, an almost direct relationship was observed between changes in slice thickness and drying time. The effective moisture diffusivity coefficient in peach slices increased with an increase in slice thickness, temperature, and air velocity and ranged from 9.57 × 10^-10 to 4.33 × 10^-9 m^2/s under different experimental conditions. The calculated activation energy for drying peach slices under experimental conditions ranged from 16.74 to 20.48 kJ/mol. The designed model for simulating the drying conditions was based on an adaptive neuro fuzzy inference system (ANFIS) with input and output membership functions of triangular and linear shapes and a hybrid learning algorithm. The model could simulate the drying process with a correlation coefficient of 0.979.

Study on characteristics and mechanism of re‐entrainment in intake filtration components of the gas turbine

AbstractAiming at the problem that the droplet re‐entrainment in the intake filtration components affects the gas intake quality and the safe operation of gas turbines, the characteristics and mechanism of the re‐entrainment in a marine double‐hook inertial stage filter are studied, and the distribution of liquid film and re‐entrainment under different inlet air velocities and droplet size distributions are compared. The results show that, due to the influence of inertia and turbulent dispersion, droplets tend to deposit on draining hooks and the lower surface of the leeward side of the blade to form a liquid film. Film stripping is the main form of re‐entrainment under ship‐driving conditions. Due to the high airflow velocity and the large film thickness, hook peaks are the most prone to film stripping, and the critical airflow for film stripping velocity is 14.8 m/s. With the increase of the inlet air velocity, the film thickness at the draining hooks increased first and then decreased, and the film stripping positions were extended from the hook peaks to the rear. Different droplet size distributions mainly affect the liquid film thickness at the draining hook and leeward side of the blade, which in turn affects the film stripping mass.

Two-phase flow dynamics study in the trapezoidal gas channel of PEM fuel cell based on lattice Boltzmann model

ABSTRACT Water management is a critical challenge in ensuring the performance and durability of low-temperature proton exchange membrane fuel cells (PEMFCs). This study utilizes the phase-field lattice Boltzmann method to conduct three-dimensional numerical simulations, investigating the dynamics of two-phase flow in the cathode gas channel (GC) of PEMFC with a trapezoidal cross-section. The effects of the water inlet location, the surface wettability of GC, the open angle of GC, and the air velocity on liquid water distribution and discharge are analyzed. The results indicate that positioning the water inlet in the middle of the GC significantly enhances PEMFC performance while having minimal impact on average pressure drop. A wall contact angle of 70° or 110°Can optimize fuel cell performance from different directions. Setting a wall contact angle at 70° optimizes gas flow stability and maintains a low-pressure drop value for the GC. A wall contact angle of 110° focuses on optimizing gas reactant diffusion ability into porous electrodes and GC drainage rate. An opening angle of 55° for the trapezoidal gas channel improves overall fuel cell performance. Increasing air velocity facilitates the film flow formation of liquid water on top wall surfaces within the GC.

Effect of liquid nitrogen spray freezing on the ice crystal size and quality of large yellow croaker

Large yellow croakers (Larimichthys crocea) were frozen by liquid nitrogen spray freezing (LNSF), liquid immersion freezing (LIF), and air freezing (AF), and the freezing rate, ice crystal size and product qualities were compared. LNSF was found to be a promising freezing technology because of the significantly (P < 0.05) shortest freezing time, smallest ice crystal, and best overall product quality. Then, the effect of processing parameters during LNSF on freezing characteristics, and microstructure and qualities of samples was studied. Freezing time was reduced by decreasing freezing temperature and increasing air velocity. A size uniformity index was proposed in this study to evaluate the distribution uniformity of ice crystals. The minimum cross-sectional area (605.83 μm2) with the best size uniformity was achieved at a freezing temperature of −90 °C, a final temperature of −30 °C, and an air velocity of 4 m/s, showing a reduction of 50.90% as compared to the maximum (1233.77 μm2). The qualities of samples frozen by LNSF with the aforementioned parameter values were well maintained and met the industrial standard. Therefore, the developed LNSF protocol was recommended for the industrial application for large yellow croaker.

NUMERICAL INVESTIGATION OF LIQUID-CARRYING AXIAL AND SWIRL FLOW IN A BENT PIPE

Water condensation occurs in the sloping sections of natural gas pipelines due to fluctuations in temperature and pressure. This event has a major effect on the efficiency and security of gas transportation. In this numerical study, the flow of water via a swirling flow in a wavy pipeline is examined using computational fluid dynamics. A 1-inch pipe is used to simulate a low-lying area of the pipeline, which is normally where the condensate water would gather. The effect of swirl on the flow patterns in the U-shaped pipe with previously published experimental results is studied and validated. In order to comprehend the change of static and dynamic pressure, results are extended in the doubly undulated pipe (w-pipe). According to the innovative analysis in this study, higher swirl flow could empty the water build-up faster than swirl flow inlet velocities below 11.2 m/s in a given amount of time. When the effusion volume increases and the water-carrying capacity is enhanced, several flow regimes, including annular flow, plug flow, slug flow, stratified wave flow, and stratified flow, are observed along with an increase in air velocity.

Using a Model to Compare Cooling System Design Factors For Lactating Cows

Highlights Cow mass, milk yield, solar load, air velocity, dry-bulb and dew-point temperature impact lactating cow respiration rates. Modeled respiration rates align with published studies dealing with milk yield, solar load, and evaporative cooling. The model can be used to assess cooling systems for conditions that might be difficult to capture in field measurements. Abstract. The risk of lactating cows experiencing heat stress is increasing because of increased productivity. A steady-state process-based model described by Nelson and Janni (2023) and assessed by Janni et al. (2023) was used to compare additional combinations of environmental conditions (e.g., air dry-bulb and dew-point temperatures, air velocity, solar load) and lactating cow characteristics (e.g., body mass and daily milk yield) on modeled respiration rate. Respiration rate was linked to qualitative heat stress levels, based on work by Renaudeau et al. (2012). The model demonstrates how cows with greater body mass have larger inspired volumes of respired air (i.e., liters per minute) because they have larger tidal volumes (i.e., liters per breath) while they have lower respiration rates (i.e., breaths per minute) compared to cows with smaller body masses. The modeled results support previous studies that demonstrated heat stress increases with greater daily milk yields, solar load, and air dry-bulb and dew-point temperatures. The model finds conditions where increasing air velocity at cow level can help cows reduce heat stress levels due to solar load, and high air dry-bulb and dew-point temperatures. A comparison to a field study demonstrates the need to align field data collection and model input needs to explore the actual or potential impacts of mitigation methods like shade, evaporative cooling, and air velocity (i.e., via fans). This report demonstrates how the model can be used by engineers to investigate the impact of ventilation system designs on respiration rates using current and future technologies. Keywords: Air velocity, Cow mass, Dairy, Dew-point temperature, Dry-bulb temperature, Heat stress, Milk yield, Respiration rate, Solar load.

CFD structural design of an intake air louver for low pressure drop and high large particle separation efficiency

Due to the inadequate separation efficiency of current louver used in industrial, commercial, and residential buildings in separating large particle, leading to clogging of subsequent high-efficiency filters and increased fan energy consumption. Therefore, it is essential to increase separation efficiency of large particle for fresh air intake to reduce the burden on the filter. In this study, a novel louver has higher large particle separation efficiency with lower pressure drop was developed based on experiments and computational fluid dynamics (CFD) model. The effect of different structural parameters (number, length and location of dustproof hooks) and inlet air velocity on separation efficiency and pressure drop was evaluated. Results showed that mentioned factors could pose important impacts on pressure drop and separation efficiency. With the increase of inlet air velocity from 2.3 m/s to 2.8 m/s, the separation efficiency of the louver was decreased from 80.3 % to 57.3 %, while the pressure drop of the louver was increased from 11.1 Pa to 13.9 Pa. In addition, when inlet air velocity was 2.8 m/s, compared with the commercial louver, the pressure drop of louver was reduced by 89.5 %, the large particle separation efficiency was increased by 158.6 %.

Venturi effect-based simulation of air-based PVT optimization

ABSTRACT Air-based photovoltaic thermal(PVT) solar collectors can convert solar energy into both electrical and thermal energy. However, the output efficiency was often low due to the limitation of the heat transfer capacity for air. Therefore, in this paper, an air-based PVT with the application of a novel rib was modeled and numerically simulated. The innovation of this paper was proposing a novel rib, which was based on the Venturi effect. First, the effects of the new rib control parameters on the performance of the PVT system were analyzed using orthogonal design tests. The result showed that the thermal efficiency of the best factors combination test was 51.16% when the solar radiation was 500 W / m 2 and the air inlet rate was 0.09 m / s . Second, analyzing the fluid flow characteristics and the enhanced heat transfer mechanism, this study found that the increased air velocity under the novel rib and the low-velocity vortex formed between the rib both negatively affected heat transfer. Consequently, this paper proposed a novel fin design coupled with curved fins to address the issues with the novel rib design, which achieved 55.12% thermal efficiency with the combination structure. Finally, we applied the combined structure to the PVT system, studied its thermal efficiency under real-world conditions, and compared it with the empty channel collector. The results showed significant improvement, with a 16.38% increase in thermal efficiency and the model exhibited excellent, stable performance.

Experimental study of the influence factors of the droplet size of rotary nozzles during manned helicopter spraying operations

The droplet size significantly affects the performance of aerial spraying operations. Thus, it is crucial to develop rotary nozzles for helicopter spraying operations and analyze the influence of droplet size. We conducted a calibration test of the nozzle rotation speed to analyze the effects of air velocity, blade installation angle, hub diameter, and blade length on the rotation speed. The results showed that the rotation speed increased with an increase in air velocity and nozzle diameter and decreased with an increase in the blade angle. The rotation speed of three types of rotary nozzles was measured in the range of 576–15 358 r/min. A high-speed wind tunnel test was conducted to determine the droplet size of the rotary nozzles at different rotation speeds, spray flow rates, and hub mesh numbers. The influence degree of the three factors on the droplet size was rotation speed > spray flow rate > mesh number. The multiple linear regression equation of the volume median diameter (VMD) of the droplet size was obtained. The droplet size obtained from wind tunnel and flight tests at 5000 and 7000 r/min was compared. The droplet size was in the range of 148.56–259.39 μm and was slightly larger under wind tunnel conditions than during the flight test. The relative width of the droplet spectrum was small for both test methods, indicating that the droplet size distribution of the three rotary nozzles was uniform. Finally, the spray nozzles were used for insect control in forest areas and achieved a control efficiency of 94.6. This study provides a reference for optimizing the operating parameters of spraying nozzles and improving the performance of helicopter-based low-volume spraying operations.