| A suggestion of a new method for the calculation of the coating thickness in continuous hot-dip galvanizing C. M. Jo, G. Y. Kim, Y. D. Kwon and S. B. Kwon*
The Journal of Mechanical Science and Technology, vol. 25, no. 11, pp.2781-2786, 2011
Abstract : It is known that the distributions of the impinging pressure gradient and the shear stress at the strip surface play a decisive key role in
the decision of the coating thickness in hot-dip galvanizing. So, to predict the exact coating thickness, it is essential that the distributions
of the impinging wall jet pressure and the shear stress acting between the liquid film and jet stream are measured (or calculated) exactly
for each specific coating condition. So far, to obtain the impinging wall jet pressure, it was assumed that the jet issuing from an air-knife
is similar to the Hiemenz plane stagnation flow, and the wall shear stress could be predicted by an equation using the assumption of a
non-negative Gaussian profile in impinging wall jet pressure in general, so that it cannot be reliable for some impinging wall jet regions
and nozzle systems intrinsically. Nevertheless, one cannot find a suitable method to cope with the difficulties in measuring/calculating of
the shear stress and the impinging wall jet pressure. Such a difficulty which will cause an inaccuracy in the coating thickness prediction.
With these connections, in the present study, we suggest a new method named as a two-step calculation method to calculate the final
coating thickness, which consists of the air jet analysis and coating thickness calculation. And, from the comparison of the results one
may confirm the validation of the new suggested method.
Keyword :
Coating thickness; Gas wiping; Numerical analysis; Continuous hot-dip Galvanizing; Liquid pure water
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