Effects of oxide layer on Leidenfrost temperature during spray cooling of steel at high temperatures

Chabičovský, Martin; Hnízdil, Milan; Tseng, Ampere A.; Raudenský, Miroslav

doi:10.1016/j.ijheatmasstransfer.2015.04.067

Cited by 45 publications

(25 citation statements)

References 23 publications

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“…Yet, it is unclear if the actual surface conditions (e.g., clean, as-cast or covered with casting powder) play an important role in the development of scale in the secondary cooling of CC. A literature survey revealed that despite considerable interest in oxide growth during rolling, forging and stamping [1][2][3][4][5][6][7][8][9], a lack of information persists regarding the effect of surface conditions on scale formation during casting processes [10][11][12][13][14][15]. The majority of previous research has been focused on the impact of the oxide scale during secondary cooling with water sprays (i.e., after the mould), where numerical modelling is the main approach for analysis [1,10,[16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Scale Formation on HSLA Steel during Continuous Casting Part II: The Effect of Surface Conditions

Huitron

López

Vuorinen

et al. 2020

Metals

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The present research addresses the effect of surface condition on oxide scale formation at high temperatures such as those experienced during secondary cooling in Continuous Casting. Tests were carried out in clean, as-cast and surfaces covered with casting powder to replicate the oxidation/re-oxidation after the mould. Specimens oxidized at 1000, 1100 and 1200 °C under dry air and water-vapour conditions revealed that the oxide scale formation is strongly influenced by temperature, environmental and surface conditions. The oxide scale thickness increases with temperature alterations in the surface (e.g., as-cast and covered with powder) where oxides and carbonates from the casting powder accelerate oxidation kinetics leading to thick and unstable scales. A high amount of carbon is present on surfaces covered with casting powder where it diffuses through the oxide scale forming CO and CO2 which lead to stress accumulation that makes scales prone to defects such as pores, voids and micro-cracks. Ultimately, if wüstite remains attached to the steel surface or inside oscillation marks, it may disturb heat transfer during secondary cooling which has deep industrial implications for crack formation and overall casting yield. Therefore, accurate insights on scale type and growth mechanisms could lead to accurate control of its formation during casting.

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Section: Introductionmentioning

confidence: 99%

Scale Formation on HSLA Steel during Continuous Casting Part II: The Effect of Surface Conditions

Huitron

López

Vuorinen

et al. 2020

Metals

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“…Due to these facts, there is a large field for development and optimization of these systems in terms of operational parameters, chemicals used or spraying arrangement including usage of extremely broad spectrum of nozzles. Nozzles are crucial in a plethora of industrial applications including dust control [25], spray cooling [26][27][28][29][30], hydraulic descaling [31], and play a vital role in gas scrubbers as they can provide an adequate spray pattern of the absorption liquid. This is necessary to create the largest possible contact surface with gas phase to ensure process intensification, appropriate mass transfer and thus separation efficiency.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle

2019

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Spiral nozzles are widely used in wet scrubbers to form an appropriate spray pattern to capture the polluting gas/particulate matterwith the highest possible efficiency. Despite this fact, and a fact that it is a nozzle with a very atypical spray pattern (a full cone consisting of three concentric hollow cones), very limited amount of studies have been done so far on characterization of this type of nozzle. This work reports preliminary results on the spray characteristics of a spiral nozzle used for gas absorption processes. First, we experimentally measured the pressure impact footprint of the spray generated. Then effective spray angles were evaluated from the photographs of the spray and using the pressure impact footprint records via Archimedean spiral equation. Using the classical photography, areas of primary and secondary atomization were determined together with the droplet size distribution, which were further approximated using selected distribution functions. Radial and tangential spray velocity of droplets were assessed using the laser Doppler anemometry. The results show atypical behavior compared to different types of nozzles. In the investigated measurement range, the droplet-size distribution showed higher droplet diameters (about 1 mm) compared to, for example, air assisted atomizers. It was similar for the radial velocity, which was conversely lower (max velocity of about 8 m/s) compared to, for example, effervescent atomizers, which can produce droplets with a velocity of tens to hundreds m/s. On the contrary, spray angle ranged from 58° and 111° for the inner small and large cone, respectively, to 152° for the upper cone, and in the measured range was independent of the inlet pressure of liquid at the nozzle orifice.

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“…After the semi‐solidified steel slab is withdrawn from the mold by rollers located below the mold at cast speed, it enters the secondary cooling section, where an array of high‐pressure nozzles spray cooling water, or air‐mist, across the slab surface to extract heat and allow the slabs to completely solidify. Then, the solid slab is cut at a preferred length and sent to another facility to be reheated so it can be thinned and shaped to a desired form …”

Section: Introductionmentioning

confidence: 99%

Modeling of Spray Cooling with a Moving Steel Slab during the Continuous Casting Process

Lee

Tang

et al. 2018

steel research int.

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During continuous casting secondary cooling, heat is removed from slab surface through spraying water from arrays of nozzles. Efficient and uniform heat removal without causing slab cracking is desired. The present study focuses on the development and validation of a reliable numerical model which can accurately predict spray formation from flat‐fan atomizers and the heat transfer between impinging droplets and a moving hot steel slab. Water droplets are considered as the discrete phase and are tracked in a Lagrangian framework to allow detailed modeling of breakup, coalescence, and impingement. The droplet size and the heat transfer coefficient on the slab surface are validated. Both simulations show good agreements with the experimental measurements in the center of the spray, where fine droplets are generated through multiple collisions. After droplets impinge on the slab surface, a narrow low temperature region is created inside the spray coverage, and the relative motion of the spray shifts the coverage toward the upstream. Future studies are necessary in order to improve the prediction of droplet‐air interaction near the edge of the spray, where small droplets tend to coalesce and form large ones due to a lower possibility of collision.

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Effects of oxide layer on Leidenfrost temperature during spray cooling of steel at high temperatures

Cited by 45 publications

References 23 publications

Scale Formation on HSLA Steel during Continuous Casting Part II: The Effect of Surface Conditions

Scale Formation on HSLA Steel during Continuous Casting Part II: The Effect of Surface Conditions

Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle

Modeling of Spray Cooling with a Moving Steel Slab during the Continuous Casting Process

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