Quenching is an important process step in the heat treatment of metallic materials in continuous strip lines, as it is crucial to the resulting material properties of the final product. For many modern high-strength materials, the required cooling rates cannot be achieved while using conventional gas cooling systems. Therefore, the material has to be cooled with water. Water can be applied to the strip’s surface using a spray nozzle field, which is particularly challenging in regards to temperature homogenei-ty. Furthermore, strips in continuous lines are often run horizontally, which causes water flow on the surface. This flow has a non-negligible influence on the tempera-ture homogeneity during cooling, which in turn determines the quality of the final product. Consequently, a better understanding of spray nozzle fields and the flow on the surface is of interest and, therefore, investigated by the authors.
To examine these phenomena two test rigs have been setup at the Department for Industrial Furnaces and Heat Engineering at RWTH Aachen University. One for in-vestigating water flow on a moving strip and one with a steady horizontal surface. With these test rigs, the influence of several important parameters (e.g. nozzle pres-sure, nozzle-to-surface-distance, strip speed, etc.) on the flow in nozzle fields can be determined in a wide range. This is achieved by a combination of several different measurement methods. Alongside a self-developed measurement methodology, which allows the qualitative and quantitative determination of the flow, the droplet impact on the surface is measured. Additionally, the water impingement density, an important parameter for the description of spray nozzles and nozzle fields, can be measured in one of the test rigs. Finally, the generated data of the used measure-ment methods are correlated for a better understanding of the generated water flow on surfaces and its dependence on the proposed parameters.
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