Simulated and experimental results on heat recovery from hot steel beams in a cooling bed applying modified solar absorbers

In recent years, the steel industry has undertaken efforts to increase energy efficiency by reducing energy consumption and recover otherwise lost heat. About 60% of the energy consumed in a steel plant is lost in cooling beds where the hot steel beams are cooled down by natural convection and radiation. In this paper, the potential of heat recovery by radiation in a cooling bed was determined. Firstly, numerical simulations of the heat flux were done and validated with experimental measures. Secondly, a pilot test to recover the heat with modified solar absorbers was installed at the side of the cooling bed. The standard solar panels were painted with high absorption paint in the wavelength range of the hot beams. The results showed that up to 1 kW/m2 could be recovered with a temperature of 70°C at the side of the cooling bed, with a thermal efficiency of approximately 40%. As the experimental results were promising, further research is suggested to find an adequate selective coating and glazing. This would maximize the absorption at the wavelength range of the hot beams and minimize the emissivity at operational temperature of the absorber (100°C). Additionally, it would be of interest to find the optimum position for the absorbers in the cooling bed, which maximizes the heat recovery and does not interfere in the production process.