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Development of flat flame burners for industrial heat transfer applications

Castañeda Gutierrez Otero, Victor 2019. Development of flat flame burners for industrial heat transfer applications. PhD Thesis, Cardiff University.
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Abstract

Several industrial processes involve the heating of long and thin strips. One such process is the decarburising annealing of electrical steel. Published research suggests that rapid heating of up to 100◦C/s during the decarburising annealing process significantly improves the magnetic properties of these steels. In this investigation, it was shown that the currently used technology of radiant tube burners was not optimal for the heating of these type of products. Therefore, the main objective of this project was to develop a novel type of burner that produced a flat wall attached flame by means of the Coanda effect. Due to its unique flame geometry, the burner achieved the required heating rates. The behaviour and fundamental characteristics of isothermal and reacting Coanda flows were investigated. A combination of laser diagnostics, temperature measurements and visual observations were used to obtain information about the flow. A precessing vortex core that contributes to the flat flow profile was identified. A hysteresis behaviour between different flow states was observed. Critical factors that affect the onset and stability of the Coanda flame were determined; being the most relevant ones the applied swirl intensity, the flow rate, the relation between plate height and the nozzle outlet, the equivalence ratio and the nozzle geometry. Subsequently, the experimental results were used to validate numerical simulations. The numerical simulations were used to conduct a parametric analysis for the burner geometry optimisation. The optimised burner was compared to a radiant tube burner via CFD simulations. It was found that the Coanda burner had lower radiant heat flux than the radiant tube burner. However, this downside was compensated by an increase in the total radiating area in the furnace. The use of the proposed Coanda burner in the decarburising annealing process had the potential to cause an increase in heating rate, a reduction in energy requirement, a reduction in NOx emissions, a reduction in heating time, an increase in temperature homogeneity of the load, and a reduction in volume furnace with the consequential reduction in start-up times. Thus, the proposed technology has the potential to reduce the energy intensity of the annealing process and, because of the increased heating rate, improve the magnetic properties of the final product.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Steel Annealing; Coanda Effect; CFD; PVC; Flat Flame Burner; Heat Transfer.
Date of First Compliant Deposit: 13 August 2020
Last Modified: 13 Aug 2020 08:55
URI: http://orca.cf.ac.uk/id/eprint/134148

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