Numerical Analysis of Cooling Characteristics for Water Bar

Abstract

SynopsisThe cooling process of a hot steel plate by a cylindrical water flow was studied experimentally and analytically in this paper.The cooling characteristics were examined on the basis of cooling curves obtained under various experimental conditions. A numerical model was built up to calculate the relation between temperature and time at a given point of the steel plate during cooling. Then, the heat transfer coefficient on the water cooling zone was found out so that the cooling curve calculated by the numerical model became equal to the experimental result.The main results obtained in this paper are as follows:(1) The heat transfer coefficient on the water cooling zone may be considered to be proportional to square root o f the defence between the plate surface temperature and the water temperature;where, BS, Bw : The temperature of the plate surface and the cooling water, respectively.(2) The black zone is formed on the initially hot red plate surface, as soon as the water strikes the plate. The radius of the black zone expands approximately in proportion to square root of the cooling time.(3) The theoretical cooling curves were found to match with the experimental ones by the appropriate combination of the heat transfer coefficient on the water cooling zone and the growth rate of the zone. Here, a=500 (0S-o )'~2 as the heat transfer coefficient (kcal/m2h°C) and Rw=RB+10.0 as the water cooling radius (mm) were used in this calculation, where RB indicates the black zone radius.

Effect of surface thickness on the wetting front velocity during jet impingement surface cooling

“…In another work Akmal et al [2] for horizontal cylindrical steel surface of 7.82 mm thickness at 500 °C initial temperature found the wetting front velocity as 28.9 and 2.5 mm/s respectively at 19 and 26 mm downstream locations with the jet of 3 mm diameter and jet velocity of 5.0 m/s. Moreover, based on experimental results, Hatta et al [32] correlated the wetting radius merely in term of time, without considering any other operating parameter. Therefore, these relations cannot be used for comparing the present experimental results.…”

Effects of Cooling Water Supply Nozzle Array on Cooling Performance of Run Out Table in Hot Rolling Process

“…[5][6][7] However, as previously mentioned, because the cooling result is very sensitive to variations of the side factors, very wide-ranging results have been predicted according to experimental conditions. Therefore, it is necessary to describe the phenomenon exclusively for small changes in operating and design parameters.…”

Fully Numerical Analysis for Effects of Cooling Water Flow Rate and Plate Running Speed on Steel Plate Cooling in Very High Temperature Region

“…[2][3][4][5] As discussed in previous work, 1) since the process is closely connected with the thermal-fluidic behavior of the residual water accompanying with the impinging jet motion, the plate running motion, the heat transfer between the hot steel plate and the cooling water, and the complex effect of these factors, the perfect similarity between the laboratory scale and the real scale cannot be achieved. Hence a lot of researchers have conducted real scale experiments [6][7][8][9] not to be retained on a laboratory scale.…”