Ultra fast cooling of hot steel plate by air atomized spray with salt solution

• Published in: Heat and mass transfer Vol. 50; no. 5; pp. 587 - 601
• Main Authors: Mohapatra, Soumya S., Ravikumar, Satya V., Jha, Jay M., Singh, Akhilendra K., Bhattacharya, Chandrima, Pal, Surjya K., Chakraborty, Sudipto
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2014
• Subjects: Engineering; Engineering Thermodynamics; Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Original; Thermodynamics; Critical Heat Flux; Water Flow Rate; Atomize Spray; Spray Cool; Surface Heat Flux
• ISSN: 0947-7411; 1432-1181
• DOI: 10.1007/s00231-013-1260-6

In the present study, the applicability of air atomized spray with the salt added water has been studied for ultra fast cooling (UFC) of a 6 mm thick AISI-304 hot steel plate. The investigation includes the effect of salt (NaCl and MgSO
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) concentration and spray mass flux on the cooling rate. The initial temperature of the steel plate before the commencement of cooling is kept at 900 °C or above, which is usually observed as the “finish rolling temperature” in the hot strip mill of a steel plant. The heat transfer analysis shows that air atomized spray with the MgSO
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salt produces 1.5 times higher cooling rate than atomized spray with the pure water, whereas air atomized spray with NaCl produces only 1.2 times higher cooling rate. In transition boiling regime, the salt deposition occurs which causes enhancement in heat transfer rate by conduction. Moreover, surface tension is the governing parameter behind the vapour film instability and this length scale increases with increase in surface tension of coolant. Overall, the achieved cooling rates produced by both types of salt added air atomized spray are found to be in the UFC regime.