The impact of hydrogen fuel switching on the heat transfer from flames in industrial heating applications

White, Benjamin 2025. The impact of hydrogen fuel switching on the heat transfer from flames in industrial heating applications. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis investigates the impact of hydrogen fuel switching on an industrial heating process, motivated by the urgent need to decarbonise. This motivation arises from the increasingly strict climate regulations imposed on carbon emitting industrial sites. Hydrogen has emerged as a promising alternative fuel to natural gas for high temperature heating applications, but practical studies on the radiative and convective heat transfer from hydrogen-methane blended flames represents a clear research gap, which this thesis directly targets, evaluating the following hypothesis: “The radiative and convective heat transfer from a flame will change when the fuel is switched from natural gas (methane) to hydrogen.” Two experimental rigs were used to assess the heat transfer characteristics of hydrogen and methane combustion, both as pure fuels and as blends. Radiative and convective heat flux, flame length, visibility, chemiluminescence intensities, boiler tube simulator performance, and NOx emissions were measured. The experimental results were then applied to a strategic risk and opportunity study, applying the experimental findings to the subject of hydrogen fuel switching in industry. The findings suggest that hydrogen blending greatly influenced heat transfer. Maximum radiative fractions were observed for 25-50% hydrogen blends. Beyond 50% blending, radiative fraction decreased. The location of maximum radiative heat flux was 50-70% along the flame’s length. Increasing the geometric swirl number of a burner was shown to reduce flame length and radiative fraction. Chemiluminescent intensity ratios, such as C2 ∗/OH∗ at the root of the flame were shown to correlate well with the radiative fraction of the entire flame. The chemiluminescent intensities of OH∗, CH∗, C2 ∗, Na∗ and H2O were also assessed. Hydrogen combustion improved convective performance in the boiler tube simulator experiments but also increased NOx emissions, requiring careful management of this trade-off. Air-fuel control strategies influenced how this trade-off was navigated.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Engineering
Uncontrolled Keywords:	1. Hydrogen 2. Methane 3. Heat Transfer 4. Combustion 5. Flames 6. Industrial 7. High Temperature 8. Radiation 9. Convection 10. Furnace 11. Boiler 12. NOx
Funders:	EPSRC CDT RDFES
Date of First Compliant Deposit:	19 May 2026
Last Modified:	19 May 2026 13:55
URI:	https://orca.cardiff.ac.uk/id/eprint/187011

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