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In this work the single-nozzle spray cooling on a large scale industry-used drum wall has been simulated by a verified numerical model. For a certain spray nozzle, the effects of four parameters, i. e. different spray pressures, different spray heights, different water temperatures, and different wall temperatures, on heat transfer have been analyz...
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... Because of the complexity of two phase flow in evaporative cooling and participation of a lot of attendant parameters in it, numerical studies are more prevalent than the experimental studies [11]. These numerical investigations were carried out for inlet air flow of cooling towers, hot plates, air-cooled condensers, heat exchangers and other thermal components [12][13][14][15]. ...
In hot and dry climates, evaporative cooling of the air by water spray can be applied in several requirements, such as evaporative condensers which the airflow is precooled by the water spray before it reaches the condenser. The interaction between water droplets and the air is a complicated two-phase flow that is affected by the several parameters. Here, an Eulerian-Lagrangian 3D model was developed to investigate the influence of important parameters on spray cooling performance in a rectangular duct. The evaluated parameters include the number of nozzles, inlet air flow rate, and spray water flow rate. The results represented that growth in the number of nozzles causes a reduction in the spray cooling efficiency. This is due to decrease of droplets retention time within the duct by increasing the number of nozzles at a constant total spray flow rate in the cases. The maximum and minimum spray cooling efficiency belong to the cases with one nozzle at water flow rate of 20 l/h and four nozzle at water flow rate of 5 l/h, respectively. The difference between spray cooling efficiency at 3 and 4 number of nozzles is less than 1.8%. Moreover, increasing the air flow rate from 0.5 l/h to 2 l/h (by 300%) makes a decrease in the spray cooling efficiency up to 58.6%.
... where l/D is the ratio of the length to the diameter of the mixing chamber; a tph is a twophase flow sound speed; n loc , n trresistance coefficients: local and friction along the length. The calculation of the processes of heat and mass transfer during the droplet evaporation in the thermopressor working chamber was carried out according to the classical equations by the well-known methods [34][35][36]. ...
Circuit solutions of cooling systems by using thermopressors were developed and analyzed in the article. The efficiency of the thermopressor application for the charge air cooling system with single-stage compression was analyzed. A method of the fine water atomization into the charge air by a thermopressor was proposed for contact cooling of the charge air and ecological humidification of the charge air at the inlet to the engine cylinders. The use of a thermopressor makes it possible to realize the effect of thermo-gas-dynamic compression. This effect increases the pressure while simultaneously decreasing the temperature during the finely dispersed water evaporation injected into the airflow, moving near the sound speed. Moreover, contact cooling of the charge air by using thermopressors does not require complex mechanical spray systems. The reduction in the power consumed by the compressors was 7–12%, due to which, in turn, it was possible to increase the power of the internal combustion engine by 1–2%.
... Spray heat transfer has the properties of high heat flux, high heat transfer coefficient, excellent temperature uniformity and no contact thermal resistance with the heating surface and thus is superior to conventional heat transfer [8][9][10]. Fast and uniform heating of feedstock could be achieved through spray heat transfer between the atomized feedstock and surface of SiC bed heated by microwave. ...
The heat transfer characteristics of the microwave heating coupled with atomization feeding were investigated using ethanol as the spray medium on a pressure swirl nozzle. The effects of spray height, flow rate and temperature on the sauter mean diameter (SMD) of atomized droplets were examined. The results showed that the droplet SMD was 12-130 ?m, which increased with the spray height and decreased with the flow rate and temperature of spray medium. Through the fitting of the experimental data, the dimensionless correlation of the droplet SMD which was based on orifice diameter, Reynolds and Ohnesorge numbers was obtained. The calculated results were basically consistent with the experimental data within 15% error. The heat transfer characteristics of atomized droplets on high-temperature surface of SiC bed heated by microwave were then investigated. The effects of spray flow rate, spray height and spray temperature on the heat transfer characteristics were examined. The power of spray heat transfer decreased with the temperature and increased with the spray flow rate and spray height. The dimensionless correlation to describe the heat transfer characteristics of atomized droplets on the high-temperature SiC surface under the microwave heating was obtained which included thermophysical properties of spray medium, spray parameters, and temperatures of the high-temperature bed surface and spray medium, with the error of ?20%. These correlations can be used to predict the SMD of the atomized droplets and the power of spray heat transfer in the microwave heating process.
... The influence of spray cooling parameters on cooling performance is often reported in the application of external nozzle [6][7], but the research on the embedded nozzle and particularly on the cooling performance of composite cooling tool is rarely. In this work, a three-dimensional CFD simulation model of the tool was built and the fluid-solid thermal coupling simulations were carried out by using Fluent software to reveal the cooling performance of the composite cooling tool. ...
In order to decrease the cutting temperature and assist the chips removal while reduce or eliminate the generation of cutting waste liquid in metal cutting process, a novel turning tool cooled by combining circulating internal cooling with spray cooling is proposed. In this paper, the cooling performance of the composite cooling tool is investigated by the combination of CFD based thermal-fluid-solid coupling analysis which were carried out by Fluent and Taguchi design. A discussion on the influence of cooling parameters on the cooling performance of the composite cooling tool is conducted. The results show that the order of the influence of each parameter on the cutting temperature is as follows: coolant temperature of circulating internal cooling, spray pressure, air temperature of spray cooling, coolant flow rate of circulating internal cooling and coolant flow rate of spray cooling. The optimal parameters in this study are: spray pressure is 0.45 MPa, coolant flow rate of spray cooling is 150 ml/h, air temperature of spray cooling is 2 °C, coolant flow rate of circulating internal cooling is 2 m/s, coolant temperature of circulating internal cooling is 2 °C.
... In this context, several numerical and experimental studies, like those presented in Refs. [23][24][25][26], were also conducted on spray cooling performance. For example, Vouros et al. [26] studied experimentally the water-mist jet issuing normal to a heated flat plate and concluded that heat flux from heated surface would influence the development of jet sprays. ...
This study is an experimental investigation of the oceanic environment effect on a plate heat exchanger performance. Indeed, an experiment was carried out on a single plate of the exchanger to generate a turbulent airflow in which fine water droplets were injected into a horizontal vein where a heated plate was placed. The experimental tests were conducted for different air velocities and various water concentrations of freshwater and saltwater. In fact, two plate forms were considered: The first one is flat while the second is corrugated. Three main facts were observed in this work: i) the correlations linking the heat transfer rate to the operating conditions, ii) the effect of fog addition and the plate form on convective heat transfers and iii) the impact of the formation of a salt layer on the surface of the plate in the case of salt water.
... Indeed, they showed that evaporation can reach 81% for water droplets of 20 mm at a velocity of 1 m s −1 and that size and air velocity have a strong impact on transport and evaporation of droplets. Recently, Chen et al. [30] presented a numerical investigation of spray cooling on curve wall. The wall temperature, spray pressure and water temperature showed dominant effects on cooling performance. ...
Water spraying is widely being used in many industrial applications because of the benefits it has shown over cooling. This paper presents a numerical investigation to simulate evaporating water spray along a plate of an exchanger. Indeed, we were interested in a horizontal channel whose lower wall is the plate of the exchanger maintained at a heating flow. This plate is exposed to a turbulent airflow in which water droplets were injected. The equations governing the continuous phases (air) and the dispersed phase (water) were developed. These equations were solved using Comsol Multiphysics. A comparison of the simulation results and those of the experiment reveals an acceptable concordance. Therefore, the numerical results present the thermal behavior by studying transversal and longitudinal evolution of temperature. Moreover, the maximum evaporated water flow (mmaxew) and the plate temperature are investigated for several physical parameters of the continuous phase, such as velocity, relative humidity and inlet temperature. The results show that these parameters have significant impact on the cooling of the plate. In addition, mmaxew witnesses a remarkable decrease by increasing relative humidity. However, increasing air velocity and inlet air temperature could improve mmaxew.
... Heat spray cooling is often utilized for high temperature quenching of metals [3] and the cooling of the superheated steam [4]. Recent studies have also focused on the heat spray cooling for electronic cooling purposes [5][6][7]. Heat spray cooling can cover a wide range of surface temperatures from cryogenic [8], medium [9] to very high surface temperatures [3]. Although heat spray cooling technique encompasses the injection of droplets in the form of spray of very small droplets and not a single droplet, insight into the interaction of one droplet with a hot surface is essential and can build fundamental understanding for spray cooling [10]. ...
Droplet impact on hot surfaces is widely encountered in industry and engineering applications. In the present paper we investigate the effect of the combination of the droplet liquid type and the solid surface type and their effect on droplet impact dynamics. We test three surfaces, copper 110, aluminum 1199 and stainless steel 304, and two liquids, water and ethanol. These surfaces and liquids are characterized by high and low thermophysical properties. The three surfaces are tested with water to investigate the effect of the surface on the droplet dynamics. After that, we test both liquids with aluminum. Our findings showed that the Leidenfrost temperature does not always correlate with the surface thermal properties as reported in the literature. Some surfaces can undergo changes because of the heating and this reduces their initial thermal properties. For this reason, such surfaces are capable to show two Leidenfrost temperatures because of the thermophysical properties reduction during heating. Our findings also revealed that the Leidenfrost temperature of liquids with low thermophysical properties including surface tension, evaporation latent heat and density show trivial effect by the droplet impact velocity; i.e. the Leidenfrost temperature show trivial increase by increasing the droplet impact velocity. Liquids with high thermophysical properties show significant Leidenfrost temperature increase by increasing the impacting velocity.
... According to Wells [6], the distribution of the size of the spray droplets influences the droplet movement and the rate of evaporation. Air velocity, cone angle, injection rate, direction of injection, and metrological condition [7][8][9][10][11][12] are important parameters that affect spray cooling efficiency. In this context, several studies have been carried out on spray cooling performance [13,14,15]. ...
Water spraying in exchanger systems is widely used to allow cooling and improving their performance. However, transfers within the spray mixture are difficult to express because the combined mass and heat are transferred between phases, which complicates the design of the spray systems. This article presents a numerical study of the influence of water volume fraction on the distribution of the temperature in a canal. A 2D numerical model of a horizontal channel was generated and the equations governing the continuous phases (air) and the dispersed phase (water) were developed. These equations were solved using Comsol multiphysics. A comparison of the simulation results and those of the experiment reveals an acceptable concordance.
... Evaporation of a droplet is used in various applications, such as spray drying, DNA mapping [1], combustion engineering [2,3], cooling system [4], etc. The modelling of sessile droplet evaporation can be carried out by applying various approaches. ...
The evaporation of a drop deposited on a heated substrate is a complex process, which combines several phenomena such as the Marangoni effect, mass and thermal transfers, etc. We developed, in this paper, a mathematical model and a numerical simulation code used to carry out an in-depth study about the evaporation of a drop deposited on a heated substrate surrounded by air. This numerical study was supported by experimental work. The numerical findings obtained showed the existence of a condensation phenomenon for certain configurations. At the beginning of the experiment, the evaporation started at the triple point. However, a local region of the interface remained relatively cold. In this region, the concentration gradient (Cv, Csat) directed from the liquid-gas interface to the air resulted in condensation of water steam. Although this phenomenon is temporary and visible only at the start of evaporation process, its study makes it possible to better understand and optimize the evaporation kinetics.
... Evaporation of a drop deposited on a substrate is considered as a complex phenomenon during which several processes, such as the Marangoni effect, mass and thermal transfers, interact. This phenomenon was widely dealt with in many research works because of its intensive application in various fields as spray drying, DNA mapping [1][2], Inkjet printing [3][4], combustion engineering [5-6-7], electronic cooling [8], cooling system [9], etc. For instance, authors, in [10][11], studied the evaporation of a sessile drop. ...
