Non-intrusive temperature measurement of particles in a fluidised bed heated by well-characterised radiation

We report an important step towards the in-situ measurement of heat transfer in particle-laden flows via direct measurement of the temperatures of fluidised particles. Laser-induced phosphorescence (LIP) was employed to provide non-intrusive, temporally resolved and in-situ measurement of suspended particles as a function of heat flux and radiation attenuation. Excitation was performed at 355 nm with a repetition rate of 1.67 Hz. Particles were transported with dry air within an optically-accessible fluidised bed and heated with a well-defined source of high-flux radiation from a 3 kW solid-state solar thermal simulator radiation to achieve heating rates in order 23,000°/s. Particle and gas temperatures were measured simultaneously with the former determined from thermo-phosphorescent emissions following excitation at 355 nm. Irradiation flux and mass loading were found to play important roles in particle and gas temperature rise. Confidence in the method was obtained by verifying internal consistency between the energy absorbed by the particles and the temperature rise of the gas phase, taking into account the variability of particle mass loading.