A generalized permittivity model for describing ash particle with respect to exposed temperature

This paper investigates a generalized model for describing the scattering created from fire generated ash particles as a function of temperature. The model has been derived to show how the complex permittivity of ash is expected to will change within fire smoke plumes. An investigation of the complex permittivity of ash with respects to different exposed temperatures has been carried out using a Nicholson-Ross-Weir (NRW) transmission/reflection method within two waveguide bands (X-Band (8.2–12.5 GHz) and Ka-Band (26.5–40GHz). A linear response in the complex permittivity was noted with respect to frequency over the two bands illustrating a weakly dispersive medium. The measured permittivity for naturally dries biomass was measured at εr= 2.3, heading towards that of free-space once the biomass was burnt. Finally, Using image processing techniques a probability distribution functions for describing the median complex permittivity of ash created within a fire was approximated.