Non-Contact Temperature Measurement
Emissivity of Rough Oxidised Steel Surfaces - Electomagnetic scattering
In industry a knowledge of the emissivity of steel sheets is essential in the determination of the sheet surface temperature which, to a large extent, controls the metallurgical properties of the steel. The temperature is usually `measured' by an optical pyrometer or microwave radiometer which uses a given emissivity to obtain the surface temperature. Therefore an accurate knowledge of steel surface emissivity is necessary for a good estimate of the true surface temperature. Since hot steel sheets are often covered in multiple layers of iron oxides which have built up on the steel at high temperatures, the calculation of the emissivity is no longer a simple task. The iron oxides are both varied in their layer thickness and statistically rough so that a study is required in order to ensure the currently used emissivity quantities correspond to reality.
One way of accurately determining the emissivity of a surface is through its electromagnetic reflectivity. This requires a theoretical model taking into account the electromagnetic interference effects of multiple layers with varying material properties such as permeability, conductivity and permittivity. In addition, these properties vary with temperature especially at high temperatures where the iron oxides: Wustite, Haematite and Magnetite become semi-conducting.
My study attempts to analyse these issues with regard to various types of rough surface eg plane layered surfaces, non-layered periodic surfaces, layered periodic surfaces and finally fractal layered surfaces. This study is conducted by the use of Kirchoff high frequency electromagnetic scattering theory exemplified by texts such as the older Beckmann and Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces, or the excellent, Theory of Wave Scattering from Random Rough Surfaces, by Ogilvy. This study and the subsequent papers were a result of my MSc research, two of which are currently available under the publications list below.
Other Useful ReferencesOther books which cover the same material using the above and other approaches include:
One way of accurately determining the emissivity of a surface is through its electromagnetic reflectivity. This requires a theoretical model taking into account the electromagnetic interference effects of multiple layers with varying material properties such as permeability, conductivity and permittivity. In addition, these properties vary with temperature especially at high temperatures where the iron oxides: Wustite, Haematite and Magnetite become semi-conducting.
My study attempts to analyse these issues with regard to various types of rough surface eg plane layered surfaces, non-layered periodic surfaces, layered periodic surfaces and finally fractal layered surfaces. This study is conducted by the use of Kirchoff high frequency electromagnetic scattering theory exemplified by texts such as the older Beckmann and Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces, or the excellent, Theory of Wave Scattering from Random Rough Surfaces, by Ogilvy. This study and the subsequent papers were a result of my MSc research, two of which are currently available under the publications list below.
Other Useful ReferencesOther books which cover the same material using the above and other approaches include:
- Wave Scattering from Statistically Rough Surfaces by Bass and Fuks.
- Wave Scattering from Rough Surfaces by Voronovich.