An experimental study of heat transfer in pulsed fluidised beds via infrared thermography

This work investigates the heat transfer process in a quasi-2D pulsed fluidised bed, created by applying a pulsating gas flow around the state of minimum fluidisation. Heat transfer characteristics are quantified using infrared thermography (IRT). Digital detail enhancement and image restoration are employed to enhance image quality, minimise noise, and facilitate identification of local temperature fields. Under conditions close to minimum fluidisation, an oscillatory flow allows for the mixing of the solid phase, providing up to a 19% increase in the average overall heat transfer coefficient compared to a constant flow condition, while also leading to more homogeneous local mixing. Analysis of the local temperature fields suggests that bubble patterns formed by an oscillating gas flow lead to the creation of compartments, akin to Rayleigh-Bénard convection cells. The oscillatory flow regulates spatial and temporal temperature distributions in the solid phase and enhances powder mixing without the need to increase the gas flow rate. These findings highlight some advantages of using oscillating, dynamically structured fluidised beds to intensify gas–solid operations operating at a low gas throughput.