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This paper developed a three-dimensional model to simulate the process of atomization and liquid film formation during the air-blast spray cooling technological process. The model was solved using the discrete phase model method. Several factors including the thermodynamic characteristics of the liquid film as well as the spray quality with differe...
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Plain-jet airblast atomizers are widely used in industrial applications. The literature contains numerous papers on Sauter mean diameter, however, there is no estimation method available for spray cone angle, SCA, which derivation is the primary goal of this study. Four distinct, practical model liquids were analyzed: distilled water, diesel oil, l...
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... A somewhat popular method is a simulation analysis in addition to experimental measurement. Li et al.(2020) created a 3D model to simulate the atomization and liquid film formation processes during spray cooling and investigated the effects of spray height and spray mass flow rate on the average diameter of spray droplets. Ishimoto et al.(2007) investigated the process of liquid film breaking and spray droplet formation at orifice outlet by three-dimensional numerical simulation. ...
Pressure swirl nozzles are widely applied in spray cooling, dust removal, and fuel injection. To better connect the nozzle structure with the internal flow to analyze their influence on spray parameters, this paper designs a nozzle structure and uses experimental measurement and computational fluid dynamics simulation methods to investigate the influence of the nozzle's tangential velocity to axial velocity ratio ( v τin / v zin ) and the swirl diversion channel eccentric distance ( d l ) on the spray parameters. A phase Doppler particle analyzer was used in the experiment study to determine the spray axial velocity ( v z ) and sault mean diameter ( D 32 ). In the simulation investigation, the Eulerian multiphase flow model was used to calculate the multiphase flow field of the spray. The results showed that d l and v τin / v zin both have an obviously linear relationship to the peak location ( r peak ) of each spray parameter. It means that d l plays similar roles as the v τin / v zin , which can enhance the swirl strength inside the nozzle and increase the spray cone angle. The r peak of liquid phase volume fraction ( α w ) and D 32 of the droplet particle are always greater than the r peak of v z . The analysis of the flow field inside the spray orifice indicates that as the v τin / v zin rises, the liquid in the nozzle orifice tends to move farther from the central axis, causing atomization to occur more upstream. This study serves as a reference for the flow analysis and structure design of the pressure swirl nozzle.
... The Eulerian wall film (EWF) model was employed to calculate the distribution of the coating film thickness on the targe plate. 16,35 When the liquid droplets in the spray flow field impinge on the plate and deposit to form a coating film, the mass and momentum of the liquid phase are removed from the twophase flow and added as source terms to the mass and momentum conservation equations of the liquid film, respectively. Therefore, the thickness of the coating film can be calculated through the mass and momentum conservation equations of the liquid film. ...
Uneven coatings with overspray often occur to the target plate when using a pneumatic atomizer. This issue is mainly due to the high-level pressure in the plate center, which results from unreasonable design of the structure and operating parameters in atomizer. In this paper, an optimal design for these parameters was established by response surface method (RSM) and computational fluid dynamics (CFD) to produce more uniform coatings. The velocity data measured by a hot-wire anemometry experimentally verified the numerical model. Then, annular air hole diameter, horn flare angle, annular air pressure, and shaping air pressure were selected as design variables while the central pressure was chosen as objective function. The RSM with the central composite design (CCD) was employed to construct the regression equation that expresses the relationship between the central pressure and design parameters. Finally, the optimum combination of the parameters was carried out for reducing the central pressure, and the interaction effects between the parameters were also analyzed. The optimization results show that the central pressure is decreased by 44.6% and the performance of droplet size distribution is significantly improved. The experiment confirmed the effectiveness of the optimized atomizer to obtain well-distributed coatings.
... Gas bubbles in moving droplets undergo transformation even on a short section of their way due to their movement and collisions, as shown by Xu et al. [15]. Li et al. [16] performed three-dimensional modeling of liquid film formation during liquid spray in industrial cooling systems. The calculations showed that at a high atomization rate, the composition of the aerosol cloud hardly changes when it moves away from the nozzle. ...
The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400–500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.
... On the other hand, the numerical analyses about spray cooling process in current literature were performed considering constant properties for solid parts [17][18][19]. In this paper, the variable properties were applied on the steel blank during spray cooling process and temperature dependent thermal properties are used to calculate the temperature distribution of steel blank in 3D transient conditions. ...
... In the current literature, the numerical calculations include spray cooling period were performed with constant properties for solid parts, in general [17][18][19]28]. In this study, the variable properties were applied on the steel blank during spray cooling process and temperature dependent thermal properties are embedded into 3D transient simulation by using user-defined function (UDF) code that you can write a computer program with the Fluent solver to enhance the standard features of the code. ...
In this paper, a three dimensional Computational Fluid Dynamics Model (CFD) model was generated for spray cooling of straight parts by using a single point nozzle. The numerical simulations of spray quenching were performed to investigate the cooling rate of a 22MnB5 hot steel blank commonly used material in the automotive industry. Experiments are carried out to examine infrared thermograph of hot steel blank surfaces during spray cooling process by using infrared thermal camera. Time dependent situations of surface temperatures, surface heat fluxes and cooling areas are investigated numerically. The 3D model with some assumptions is presented to improve the solution of numeric simulation and to meet the most appropriate acceptable results for spray cooling process. The developed 3D model will be used to investigate the heat transfer analysis of hot stamped parts during hybrid quenching to optimize the process parameters. The comparison of the numerical and experimental results showed that the presented approach can be effectively used to evaluate heat transfer during spray quenching with a single nozzle. With this research, it was clearly seen that the estimated cooling rates and the temperatures were in good agreement with the experimental cooling temperature data. By using the numerical results and experimental data obtained in this study, multi-nozzle spray apparatus which will be used to obtain different cooling rates on the parts by changing spray parameters such as spray height, spray angle, mass flow rate, the distance between nozzles and part etc. was developed for hybrid quenching process.
For intermittent spray-cooling purpose, it is essential to study the unsteady aspects of film evaporation and heat-transfer characteristics. In the present study, total evaporation time and surface temperature variations are investigated for four different liquid films (water, ethanol, n-octane, and n-hexane). The evaporation process is analyzed using a three-dimensional spray-wall impact with Lagrangian wall-film model. The evaporation process occurs in three stages; at the initial moments, most of the heat is used to raise the film temperature, and slight evaporation also exists. The film temperature rises until it reaches the liquid saturation point to evaporate at a constant rate. In the last stage, the evaporation rate decreases with time due to the accumulation of vapor in the bulk flow. The effect of heat flux and initial film thickness on the total evaporation time and the slope of its changes are investigated. The results show that the total evaporation time increases linearly with the initial thickness. Also, the molecular weight and saturation point of liquids are influential parameters after the enthalpy of evaporation. The surface temperature rises to a maximum value before reducing by the film evaporation. The maximum amount of the wall temperature depends on the liquid thermal conductivity and the evaporation rate. Finally, the effect of the initial value of the film temperature is investigated, and a correlation for estimating the total evaporation time is extracted.
Liquid impingement cooling in the form of jet or spray is an appropriate method to remove heat from small surfaces progressively utilized in industry. In this study, numerical simulations are conducted to investigate the effect of surface structure on heat transfer characteristics. Five different three-dimensional structured surfaces are investigated using Euler-Lagrangian approach. The effect of surface structures is discussed on the liquid film thickness, the liquid film velocity, and the heat flux with its uniformity for a given spray and temperature characteristics. The results show that the convective heat transfer strongly depends on both liquid film thickness and velocity. While the liquid film thickness always grows in the grooved surfaces, its velocity depends on the form and direction of the fins. The averaged values of the film thickness and velocity magnitude are almost independent of the surface temperature. Among the investigated surfaces, the parallel and circular patterns showed the best and worst performance on heat transfer characteristics, respectively.
High demand for high-power electronics and high-efficiency energy conversion has aroused the need for high efficiency cooling technology. Spray cooling is a prospective cooling strategy for high heat flux dissipation and precise temperature control. This paper aims to obtain the main challenges and future work directions for efficient practical application of the spray cooling technology through a comprehensive literature overview and comparison on the application status and prospects of spray cooling in electronics and energy conversion industries. Firstly, typical nozzle arrangements and system configurations of spray cooling systems are summarized to reveal the practical concerns. Secondly, recent advances of spray cooling in electronic industry are summarized, especially the system configurations, installation methods and more efficient system designs. Then, typical applications of spray cooling in energy storage, thermal power plant, nuclear power plant and other energy conversion industries are overviewed. Finally, main challenges and future researches to facilitate this promising cooling technology are proposed. Future nozzle structure design and multi nozzle arrangement should achieve uniform flow distribution. Reasonable drainage solutions must be investigated to avoid liquid accumulation and the orientation constraint. Full-scale tests fulfilling the practical application are urgent needed to promote industrial application of spray cooling. Optimization strategy such as incorporating waste heat reusing and peak load shifting to spray cooling are highly recommended.
