Spray Flow Rate Research Articles

Quality of Phytosanitary Application in Ricinus communis L. Cultivation

One of the main challenges in castor bean (Ricinus communis L.) crop is controlling gray mold (A. ricini), a fungal disease. Most fungicides used are contact-based, and the plant’s architecture complicates application efficiency. The objective of this research was to evaluate droplet deposition and spectrum in different parts of the castor plant canopy using various spray tips and flow rates. The experiment was conducted at the Instituto Mato-Grossense do Algodão (IMA) in Rondonópolis, MT, using a New Holland TL 75 tractor and a Jacto Columbia Cross sprayer. The results were in percentages and a 3-factor factor analysis was performed, where A (Tip) = 2 levels, B (Volume) = 3 levels and C (Position) = 3 levels ith four replications, using Scott-Knott test and software Assistat. Treatments involved two hydraulic nozzles (JAC 80015 and JAC 8002), three flow rates (120, 150, and 180 L per ha⁻¹), and three plant positions (lower, middle, upper third). Data were analyzed using the “F” test and compared by the Scott-Knott test at a 5% significance level. The results showed that spray tips influenced VMD, NMD, and product concentration, with greater deposition and coverage observed in the upper third of the plant.

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 %.

Prediction of evaporation temperature in air-water heat source heat pump based on artificial neural network

To improve the low-temperature heating stability and performance of the air-source heat pump (ASHP), a heat transfer model was established for an air-water heat source heat pump (A-WSHP) in this study. Key factors affecting A-WSHP evaporating temperature were analyzed through simulation. An artificial neural network (ANN) prediction model for refrigerant evaporating temperature was developed using fin pitch, air velocity, air temperature, spray flow rate, spray water temperature, and droplet diameter as inputs. In the winter climate of Xiangtan City, this model predicts the refrigerant evaporating temperature and regulates it by adjusting various input parameters. Results indicate that fin pitch and droplet size significantly impact the refrigerant evaporating temperature, more so than fin thickness. The air temperature (34.78 %) and spray water temperature (38.02 %) have the highest weights, while fin thickness has the least influence, with a weight of 0.75 %. The R2 value of the ANN refrigerant evaporating temperature prediction model is 0.974, indicating a good fit. By properly adjusting the heat pump fan and spray valve, changes in air velocity and spray flow rate can enhance the refrigerant evaporating temperature, leading to stable and efficient heat pump operation. This research not only provides a theoretical basis for the operational strategy of air-water heat pumps but also offers guidance for frost-free operation in low-temperature environments.

Optimization of liquid film parameters of indirect evaporative cooling system based on machine vision

The wet channel plate surface of indirect evaporative cooler (IEC) cannot be completely wet in actual working conditions, and the plate surface parameters of liquid film wetting rate and liquid film thickness are difficult to observe, and the lack of relevant experimental research and data support. Therefore, in this paper, machine vision technology will be used to experimentally investigate the wetting rate and liquid film thickness of the secondary side channel of the IEC, and the UDF interface program and the parameters of the original simulation model will be enhanced. The results show that the average and maximum errors of the first and second outlet temperatures of the corrected analytical model are reduced compared with the original model, and the average error is within 5% under different spray flow rates.

Record-high heat transfer performance of spray cooling on 3D-printed hierarchical micro/nano-structured surface

Managing high-flux waste heat with controllable device working temperature is becoming challenging and critical for the artificial intelligence, communications, electric vehicles, defense and aerospace sectors. Spray cooling, which combines forced convection with phase-change latent heat of working fluids, is promising for high flux heat dissipation. Most of the previous studies on spray cooling enhancement adopted high spray flow rates to strengthen forced convection for high critical heat flux (CHF), leading to a low heat transfer coefficient (HTC). Micro/nanostructured surfaces can enhance boiling, but bubbles inside the structures tend to form a vapor blanket, which can deteriorate heat transfer. This work demonstrates simultaneous enhancement of CHF and HTC in spray cooling by improving both evaporation and liquid film boiling on three-dimensional (3D) ordered hierarchical micro/nano-structured surface. The hierarchical micro/nanostructured surface is designed to coordinate the transport of spray droplets, capillary liquid films, and boiling bubbles to enhance spray cooling performance. Boiling inversion where superheat decreases with increasing heat flux is observed, leading to an ultra-high HTC due to the simultaneous promotion of bubble nucleation and evaporation. Unprecedented CHF is obtained by overcoming the liquid-vapor counterflow, i.e., synergistically facilitating bubble escape and liquid permeation. A record-breaking heat transfer performance of spray cooling is achieved with a maximum heat flux of 1273 W/cm2 and an HTC of 443.7 kW/(m2 K) over a 1 cm2 heating area.

Heat transfer and power consumption of an optimized low-pressure compact drizzling cooling module integrated PEMFC stack radiator

The application of nozzle-assisted spray cooling to proton exchange membrane fuel cell (PEMFC) stack radiators has shown superior performance when compared with conventional air-cooled radiators. However, challenges remain with regard to high power consumption. This study experimentally optimized a low-pressure compact drizzling module coupled with a stack radiator as an alternative spray cooling strategy. The effects of the distance between the drizzling module and the radiator (30–90 mm) were examined, along with the influence of the spray flow rate/temperature, air velocity/temperature, and coolant flow rate on the thermal performance. The results showed that among the operating variables, the impact of the drizzling distance decreased with an increase in air velocity. Moreover, the drizzling performance was significantly influenced by the spray flow rate and air velocity, with minimal impact from the coolant-side variables. Optimal thermal performance was achieved at a distance of 50 mm and spray flow rate of 0.4 LPM, resulting in a 142 % improvement in heat rejection compared to an air-cooled radiator and a 132 % increase in the air-side pressure drop. Additionally, heat rejection only decreased by 7.3 % as the spray temperature increased from 40 °C to 70 °C. Two novel empirical correlations were developed, predicting heat transfer improvement and air-side heat transfer coefficient with over 85 % accuracy. These findings underscore the potential of drizzling cooling for stack radiators in fuel-cell vehicles, while the empirical correlations offer valuable insights for the development of spray-cooled radiators for next-generation electric vehicles.

Experimental and theoretical evaluation of the effect of fluid resistance on the performance of a tubular indirect evaporative cooler

To evaluate the impact of fluid resistance on the performance of tubular indirect evaporative coolers (TIECs), a mathematical model of secondary air channel resistance was developed. An experimental setup was created to study the effects of factors such as secondary air flow rate and water spray flow rate on R2 under actual conditions. The model used the same conditions to analyze how factors like air flow, water flow, and droplet size influenced R2. The relationship between R2 and wet-bulb effectiveness (εwb) was also examined experimentally. The data from the experiments were compared to the model's predictions, showing a maximum relative error of 10 %, confirming the model's accuracy. It was found that R2 and secondary air flow rate (V2) are positively correlated, and εwb increases with R2. The experiments yielded secondary air resistances ranging from a minimum of 548.2 Pa to a maximum of 554.26 Pa. These results are valuable for selecting appropriate fans for the secondary air channel. Additionally, simulations were conducted to predict and calculate energy losses in the secondary air channel under real working conditions, providing a useful basis for future fan selection.

Experimental parametric study on two-phase spray cooling of HEF 7100 using flat spray nozzles

Spray cooling is an effective method and thus finds many applications, including thermal management and energy production. In this regard, spray cooling with flat sprays is particularly crucial in applications with space constraints, as it efficiently dissipates heat while conforming to limited spatial requirements. Flat sprays ensure a wide yet uniform distribution of coolant, making it ideal for cooling systems in compact and densely packed environments. Motivated by these advantages, in this study, we performed an experimental study on the effect of major flat spray parameters, which are the spray flow rate (160 mL/min), spray upstream pressure (2.5 and 5.0 bars), spray angle (0, 30, and 90°), spray distance (3 and 10 cm), spray temperature (23 and 61 °C) and wall heat flux (10–100 W/cm2), on the two-phase heat transfer performance. According to the results, unlike full cone nozzles, the spray distance enhances heat transfer. While the cooling rate increased with the upstream pressure, the inlet temperature had a deteriorating effect on the heat transfer performance of the system. The results also indicated that the heat transfer rate decreased with the spray angle. The spray angle-induced effect on the system performance diminished with the spray pressure and temperature. The obtained results were used to develop two correlations for single phase and nucleate boiling heat transfer in flat sprays. The findings of this study suggest that flat sprays, with their significantly lower flow rates compared to full spray cone nozzles, effectively meet the requirements for direct thermal management by offering precise control, reduced fluid consumption, and enhanced efficiency.

Study on the effect of spray flow rate on pumped compressed air energy storage system

Study on the effect of spray flow rate on pumped compressed air energy storage system

Investigation of containment spraying characteristics based on the correction of droplet evaporation shielding effects

Historically, the spray models in the accident analysis program are mostly based on the isolated droplet and ignore the shielding effects among droplets, which theoretically introduces some errors. This paper investigates the effect of multi-droplet shielding on spray evaporation by taking the containment spray systems as the research object. By discussing the correction factors, the law of droplet group shielding effects can be studied, and then the correction of the spray package can be realized by the self-programming. After that, the transient response characteristics of temperature and pressure in the containment before and after the model correction are studied by modeling the loss of coolant accident and main steam line break accident, respectively. And, this research tries to analyze the influence of the cell normalization model as well as spray parameters on the calculation results. The results reveal that the program can achieve more accurate prediction after being modified by the shielding effects, and the multi-cell model can capture the temperature stratification effects more accurately under accident conditions. Additionally, the spray temperature and spray sizes have an insignificant effect on the in-shell thermal hydraulics response characteristics, but the increase of the spray flow rate has a better effect on the mitigation of the temperature stratification effects and the suppression of the in-shell pressure. The research in this paper can provide some reference or research ideas for accurate modeling and safety analysis of accidents.

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.

The Influence of Spray Cooling Parameters on Workpiece Residual Stress of Turning GH4169.

To effectively reduce residual stresses in GH4169 workpieces, thus enhancing fatigue strength and operational lifespan, this study investigates the influence of spray cooling parameters on surface residual stresses during GH4169 turning in spray cooling conditions, utilizing both simulation and experimental approaches. A simulation model of residual stresses was established using finite element analysis when GH4169 was cut in spray cooling. The effects of spray pressure and flow rate on residual tensile stresses were analyzed. The analysis reveals that with increasing spray pressure, residual tensile stresses show a decreasing trend, gradually stabilizing. Conversely, with an increasing spray flow rate, residual tensile stresses initially decrease and then increase. The turning experiments of GH4169 were conducted under different spray parameters. After the experiment, the workpiece was sectioned and analyzed for residual stresses using X-ray diffraction instrumentation. The value residual stress measured closely matched those of simulation, with a relative error within 6%, validating the accuracy of the simulation model and confirming the appropriateness of parameter settings. These results contribute to the further promotion of spray cooling technology and facilitate the rational selection of spray parameters.

Performance analysis of a novel isothermal compressed carbon dioxide energy storage system integrated with solar thermal storage

The significant increase in renewable energy generation will lead to the unstable operation of the power system. Compressed carbon dioxide energy storage (CCES) is a promising energy storage technology, which can smooth the output of renewable energy. However, one of the disadvantages of conventional CCES is the need to store compression heat, which leads to the complex structure of heat storage units. In this paper, an isothermal CCES system integrated with solar thermal storage is proposed and modeled. The parameter variations of work fluids in the pressure vessels with time and the thermodynamic properties and economics of the system are analyzed. The results show that the round-trip efficiency is 107.14 %, the energy storage density is 5.174 MJ/m3, and the levelized cost of electricity is 0.142 $/kWh. The component with the highest exergy destruction is the regenerator, followed by the LP units. The combination of liquid spray technology can decrease the highest temperature of carbon dioxide in the pressure vessel from 358.80 K to 309.39 K and increase the isothermal compression efficiency from 78.72 % to 92.26 %. Increasing the liquid spray flow rate and decreasing the hydraulic pump flow rate can both make the actual compression process closer to the isothermal process.

Exploring the Impact of Spray Process Parameters on Graphite Coatings: Morphology, Thickness, and Tribological Properties

This study explores, through a full factorial experimental design, the effects of graphite concentration and spray flow rate on the morphology, thickness, and tribological performance of graphite coatings for potential tribological applications. Coatings were applied to rough substrates using varying concentrations and flow rates, followed by analysis of their morphological characteristics, roughness, thickness, coefficient of friction (COF), and wear behavior. The results revealed distinct differences in the coating morphology based on flow rate, with low-flow-rate coatings exhibiting a porous structure and higher roughness, while high-flow-rate coatings displayed denser structures with lower roughness. A COF as low as 0.09 was achieved, which represented an 86% reduction compared to uncoated steel. COF and wear track measurements showed that thickness was influential in determining friction and the extent of wear. Flow rate dictated the coating structure, quantity of transfer film on the ball, and the extent of graphite compaction in the wear track to provide a protective layer. SEM and elemental analysis further revealed that graphite coatings provided effective protection against wear, with graphite remaining embedded in the innermost crevices of the wear track. Low flow rates may be preferable for applications requiring higher roughness and porosity, while high flow rates offer advantages in achieving denser coatings and better wear resistance. Overall, this study highlights the importance of optimizing graphite concentration and spray flow rate to tailor coating morphology, thickness, and tribological performance for practical applications.

Spray-on steady-state study of multi-rotor cleaning unmanned aerial vehicle in operation of photovoltaic power station

By 2024, the photovoltaic industry will have solidified its position as a strategic emerging industry in China. Photovoltaic power stations are deploying solar photovoltaic panels extensively, necessitating the utmost maintenance of their cleanliness and the implementation of dust removal measures in these areas. This is crucial in minimizing the loss of light energy conversion, thus enhancing the overall efficiency of the solar energy system. Through the experimental methods of dynamic and static spraying cleaning, as well as numerical simulations based on the internal and external flow fields of spraying, the impacts of the dynamic and static behaviors, flight height, mission speed, and spraying flow rate of the multi-rotor cleaning drone on cleaning effectiveness are studied. The results indicate that the jet model of the external flow field of the drone has an incoming flow velocity of 4 m/s and a spraying flow rate of 1.7 L/min. The spraying model with a maximum pressure of 82.717 Pa in the internal flow field demonstrates stable fluid behavior and achieves a good level of spraying stability. The validation of dynamic and static spraying experiments confirmed that the optimal recommended height for accurate spraying and cleaning using the drone system is 3.0 m. The dynamic tests demonstrated that the lower height of 3.0 m also provides the most suitable spraying path, reaching 2.2 m at a speed of 0.5 m/s.Operation behaviour was assessed under three different situations ，an area of approximately 2095.2 m2 of photovoltaic panels on the Gobi Desert, 375 m2 of photovoltaic panels modules on the water surface and 875 m2 of photovoltaic panels on the roof of the multifunctional plant.Compare the spray cleaning of above areas with other forms of cleaning, this technique looks very competitive, such as manual operations.

Experimental investigation on effective aerosol scavenging using different spray configurations with pre-injection of water mist for Fukushima Daiichi decommissioning

During the decommissioning of the Fukushima Daiichi nuclear power plant, it is important to consider the retrieval of resolidified debris both in air and underwater configurations. For the subsequent retrieval of debris from the reactor building, the resolidified debris must be cut into smaller pieces using various cutting methods. During the cutting process, aerosol particles are expected to be generated at the submicron scale. It has been noted that such aerosols sizing within the Greenfield gap (0.1–1 μm) are difficult to remove effectively using traditional spraying methods. Therefore, to improve the aerosol removal efficiency of the spray system, a new aerosol agglomeration method was recently proposed, which involves injecting water mist to enlarge the sizes of the aerosol particles before removing them using water sprays. In this study, a series of experiments were performed to clarify the proper spray configurations for effective aerosol scavenging and to improve the performance of the water mist. The experimental results showed that the spray flow rate and droplet characteristics are important factors for the aerosol-scavenging efficiency and performance of the water mist. The results obtained from this study will be helpful for the optimization of the spray system design for effective aerosol scavenging during the decommissioning of the Fukushima Daiichi plant.

Dynamic characteristics of refrigerant evaporation temperature in air-water heat source heat pump

In order to improve the problem of reduced heat capacity and unstable heating ability of air source heat pump (ASHP) in the heating mode during the cold season, a heat pump evaporator using air and surface water as a heat source is designed in this paper. A heat transfer unit's calculation model of an air–water heat source evaporator is established. Experimental tests and simulation studies are conducted on the refrigerant evaporation temperature and heat pump heating performance. On this basis, a refrigerant evaporation temperature prediction model is constructed using a multiple linear regression (MLR) model. The trend of refrigerant evaporation temperature under air–water heat source is analyzed by taking the winter meteorological parameters in Xiangtan City as an example. The results show that the air–water heat source heat pump (A-WSHP) has a higher refrigerant evaporation temperature and a smaller temperature fluctuation range than the ASHP. The average values of refrigerant evaporation temperatures under the experimental conditions were 5.3 °C and 4.6 °C, respectively. The temperature fluctuation ranges were 3.8 °C-6.7 °C and 2.8 °C-7.0 °C, respectively. The A-WSHP has higher heating capacity and heating stability. Air temperature, air velocity, water spray temperature and water spray flow rate are all important parameters that affect the refrigerant evaporation temperature of a heat pump. Evaporation temperature changes are positively correlated with these factors. In the refrigerant evaporation temperature prediction model, the air temperature change has the most significant effect on the evaporation temperature, followed by spray water temperature, air velocity, and spray flow rate, whose influence weights are 82.5 %, 38.8 %, 29.4 %, and 25.3 %, respectively. Selecting different temperatures of spray water and adjusting the evaporator's inlet spray flow rate can improve the refrigerant evaporation temperature and heat pump heating stability.

Drone-mounted remote-controlled arm for monitoring and precision spraying coconut rhinoceros beetle infestations

This paper presents a low-cost (locally-assembled) drone system with a sprayer arm and a remote control for monitoring and precisely applying pesticides to coconut trees infested by the Rhinoceros Beetle. A modified RGB IP camera continuously monitors potential coconut beetle infestation points, capturing real-time spray images, and displaying the results through a smartphone interface. The system provides real-time monitoring, allowing immediate remote control of the spray operation from the ground upon detecting beetle infestations. The drone-mounted sprayer arm is controlled in response to the ground-based signals, to accurately extend or contract while effectively dispensing spray chemicals onto the target areas at the upper canopy of coconut trees. In our tests using Nam-Hom coconut trees, which averaged a height of 10.4 m, the system operated at a speed of 1.25 km/h, achieving a spraying flow rate of 0.333 l/h and a working capacity of 0.352 ha/h. The controlled spraying setup emits a solid jet, ensuring precision and effective atomization of chemicals within a distance range of 1.0 to 4.0 m from the target. The spray quality attributes (droplet size, pattern, and coverage) were not significantly affected by the wind speed. The system could potentially reduce labor costs, chemical usage, and health risks associated with pesticide application.

Thermal performance of a stack cooling radiator coupled with spray cooling for the future fuel cell electric vehicles

Proton-exchange membrane fuel-cell electric vehicles require an appropriate stack cooling radiator (SCR) system to achieve optimal performance and safe operation. However, SCR cannot achieve high heat rejection under high power demands and hot ambient conditions. Hence, either the SCR needs to be enlarged to manage heat rejection or its ability to reject heat should be enhanced. In this study, a novel low pressure drizzling-aided spray cooling system (SCR-DS) is proposed for the first time. The thermal performance results were compared with those of a high-pressure nozzle-aided spray system (SCR-NS) and a conventional SCR system (SCR-CS). Based on the results, the coolant entry temperature to the stack reduced by up to 1.78 °C, and 2.75 °C when SCR-NS and SCR-DS configurations were active, respectively. Among the various operating factors, the spray cooling performance was significantly influenced by air velocity, spray temperature, and spray flow rate. Furthermore, the experienced mean increments in the heat rejection rate were up to 71.7 % and 123.5 % for the SCD-NS and SCR-DS, respectively, compared to SCR-CS. More importantly, these configurations aid in reducing the size of the SCR by 36.2 % and 45.9 %, respectively, under the same overall heat transfer coefficient conditions. Overall, the SCR-DS configuration was more beneficial than the SCR-NS configuration in terms of thermal performance owing to the slow and steady spray on the SCR surface along with more spray coverage, which aided in better liquid convection and film evaporation.

Experimental study on 18650 lithium-ion battery-pack cooling system composed of heat pipe and reciprocating air flow with water mist

Lithium-ion batteries (LIBs) are critical power sources for portable devices, electric vehicles, power grids, and energy-storage systems. Effective thermal management is mandatory for achieving optimal battery performance. Although the air-cooling method has been investigated extensively owing to its simple structure, convenient maintenance, and low cost, it is insufficient for cooling large-scale battery packs because of its limited air-cooling capacity and unsatisfactory temperature uniformity. Thus, a reciprocating spray cooling system comprising a reciprocating air flow channel, heat pipe array, and spray nozzle is proposed herein for the efficient cooling of 18,650 LIB packs. The effects of the inlet air speed, spray frequency, and spray duty cycle on the cooling performance of the reciprocating mist cooling system and the corresponding optimal operating parameter range are analyzed. Additionally, the competitive mechanism between forced air convection and evaporative cooling is discussed. The results indicate that, compared with the case of natural convection cooling, the temperature increment of the battery pack decreases by 32.1 % under reciprocating mist cooling. Meanwhile, the maximum temperature difference reduces to approximately 3.41 °C with 3C of discharge. The spray frequency minimally affects the overall heat dissipation but induces surface temperature fluctuations in individual batteries. Increasing the spray duration per 10 s in a single spray duty cycle can reduce the average temperature of the battery pack by approximately 2 °C. Additionally, the power-allocation scheme affects the heat dissipation of the system. Decreasing the flow rate of spray cooling water and increasing the inlet air speed promote the evaporation of water mist inside the system, thus further improving heat dissipation. This study provides new insights into the design of air-cooled thermal management systems for battery packs.