Energy-Efficient Cooling and Hydraulic Descaling Systems
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ENERGY-EFFICIENT COOLING AND HYDRAULIC DESCALING SYSTEMS M. Pohanka,1 P. Kotrbacek,2 E. Bartuli,3 and M. Raudensky4
UDC 621.771
Determination of real boundary cooling conditions is a fundamental requirement for numerical models and simulations to optimize and control selected processes in metallurgy. To obtain these boundary conditions, a special method has been developed. The input temperature history of cooling is obtained from experiments. The measured data are then mathematically evaluated. Realistic boundary conditions, as the heat transfer coefficient between hot surface and the coolant, allow optimization of the cooling sections and the design of their configurations. To realize the cooling test, unique laboratory equipment was developed. It allows setting of cooling conditions close to the plant conditions. The paper presents examples of optimization of work roll cooling, examples of design of sections for in-line heat treatment of metals and procedure for designing new high-pressure descaling sections. The methodology proposed by the Heat Transfer and Fluid Flow Laboratory of the Brno University of Technology is typically used to determine the heat-transfer coefficient on the surface of high-temperature material in the applications of heat treatment, cooling of rolls of hot rolling mills, and high- pressure descaling. The methodology enables identifying the effect of nozzle water jets on the heat-transfer coefficient or on removal of high-temperature scale and leads to cooling and descaling optimization for industrial partners. Keywords: boundary conditions, rolling, roll cooling, heat treatment, hydraulic descaling.
Cooling of the Work Rolls of Rolling Mills In metallurgy, sheet mills for rolling thick workpieces offer opportunities for cooling optimization and energy saving. Earlier, the design of cooling systems for the work rolls of rolling mills was based on the use of a high flow rate of fluid to achieve a good cooling effect or the use of high pressure of fluid, which, despite the considerable power consumption by cooling systems, should extend the service life of rolls. However, these methods are very wasteful and often counterproductive. The high water flow hampers the dynamic influence of the water jets from the nozzles and, hence, reduces the intensity of cooling. It is also very difficult to control the system. The modern methods developed and successfully used at the Heat Transfer and Fluid Flow Laboratory showed that there are great opportunities to improve the situation. The concept of new roll-cooling systems is based on the optimization of the cooling process. This means achieving the best cooling characteristics at minimum energy consumption. The designing of a new cooling system involves the analysis of the thermal load on the rolls and laboratory measurements of the effect of different types of cooling and nozzle configurations. Brno University of Technology, Brno, Czech Republic. 1 E-mail: [email protected]. 2 3 4
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