Abstract
Due to the significant reduction in water droplet size caused by the strong air-water interaction in the spray nozzle, air-mist spray is one of the promising technologies for achieving high-rate heat transfer. This study numerically analyzed air-mist spray produced by a flat-fan atomizer using three-dimensional computational fluid dynamics simulations, and a multivariable linear regression was used to develop a correlation to predict the heat transfer coefficient using the casting operating conditions such as air-pressure, water flow rate, casting speed, and standoff distance. A four-step simulation approach was used to simulate the air-mist spray cooling capturing the turbulence and mixing of the two fluids in the nozzle, droplet formation, droplet transport and impingement heat transfer. Validations were made on the droplet size and on the VOF-DPM model which were in good agreement with experimental results. A 33% increase in air pressure increases the lumped HTC by 3.09 ± 2.07% depending on the other casting parameters while an 85% increase in water flow rate reduces the lumped HTC by 4.61 ± 2.57%. For casting speed, a 6.5% decrease in casting speed results in a 1.78 ± 1.42% increase in the lumped HTC. The results from this study would provide useful information in the continuous casting operations and optimization.
Highlights
Secondary cooling is critical in the continuous casting process, which was introduced in the late 1950s and is used to produce more than 90% of the steel in the world [1,2]
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The study numerically investigated air-mist spray cooling by a Spraying System Co. flat-fan nozzle during the secondary cooling in continuous casting of steel using a threedimensional computational fluid dynamics simulation
Summary
Secondary cooling is critical in the continuous casting process, which was introduced in the late 1950s and is used to produce more than 90% of the steel in the world [1,2]. The mechanisms of spray cooling during the continuous casting process are complex, but certain fundamental phenomena, such as atomization of water droplets through spray nozzles, droplet wall impingement and heat transfer, and evaporation of water droplets during or after the impinging heat transfer, have been identified by researchers over the past decades. These topics are further subdivided into two major categories: spray and impinging heat transfer. Understanding HTC distribution on slab surfaces is critical because it is a transitional parameter between spray cooling and solidification. A massive number of experiments would be required to generate correlations for each type of nozzle at different operating conditions
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