Characterization of the temperature distribution on steel tubes for different operating conditions in a reheating furnace using CFD and three different measuring methods

In the steel industry, there are a number of common methods for determining the temperature distribution of steel goods. In a reheating furnace, knowledge of the inlet and the outlet temperatures is of great importance since these temperatures have a significant effect on both the gas input to the furnace as well as downstream processes. Excessive temperature fluctuations can also be prevented, ensuring uniform temperature distribution, close to the target temperature. In this work, three different measuring methods, differing in their measuring principles, are compared and validated using computational fluid dynamics (CFD). These methods include a two-colour pyrometer and an infrared camera (IC), which measures the surface temperature of the tubes. Furthermore, local temperatures are evaluated using the results of a test tube equipped with several thermocouples. In order to verify the measurements and the CFD simulations, an additional operating condition is taken into account. The operating conditions differ in their gas distribution to the individual zones, and, thus, in the heating characteristics of the tubes. The numerical model used is based on both a steady and a transient simulation, keeping the calculation time low. In the steady state simulation, the steady flamelet model (SFM), using the detailed CH4 mechanism skeletal25, serves to characterise combustion. The heating of the tubes is depicted by means of the transient simulation. These different methods of measuring temperature show good agreement with the CFD results, and their respective advantages and disadvantages are apparent.