Development of a non-invasive optical technique to study liquid evaporation in gas-solid fluidized beds

A non-invasive experimental technique based on particle image velocimetry and digital image analysis on images acquired with high-speed cameras operating in the visual and infrared wavelengths has been developed. With this, simultaneously whole-field data on the evolution of flow patterns and particle temperature distributions in a gas-fluidized bed with and without liquid injection can be obtained. A dedicated pseudo-2D gas–solid-fluidized bed was constructed and operated with liquid injection via a nozzle spraying onto the fluidized bed.It was found that for proper processing of the data recorded with the high-speed infrared camera, combination with digital image analysis on images acquired from the visual camera is essential. The application of infrared thermography to gas fluidized beds suffers from the effects of interparticle reflections. The paper addresses the calibration procedure in detail and it is shown how to correct for this. The temperature-dependent effect of the setup window in the calibration is evaluated. To demonstrate the potential of the technique, it has been applied to dry fluidization and fluidization with liquid injection.