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A novel transient thermal characterization technology is developed based on the principles of transient optical heating and Raman probing: time-domain differential Raman. It employs a square-wave modulated laser of varying duty cycle to realize controlled heating and transient thermal probing. Very well defined extension of the heating time in each measurement changes the temperature evolution profile and the probed temperature field at μs resolution. Using this new technique, the transient thermal response of a tipless Si cantilever is investigated along the length direction. A physical model is developed to reconstruct the Raman spectrum considering the temperature evolution, while taking into account the temperature dependence of the Raman emission. By fitting the variation of the normalized Raman peak intensity, wavenumber, and peak area against the heating time, the thermal diffusivity is determined as 9.17 × 10(-5), 8.14 × 10(-5), and 9.51 × 10(-5) m(2)/s. These results agree well with the reference value of 8.66 × 10(-5) m(2)/s considering the 10% fitting uncertainty. The time-domain differential Raman provides a novel way to introduce transient thermal excitation of materials, probe the thermal response, and measure the thermal diffusivity, all with high accuracy.

As liquid bridge between particles acts an important role in the particle system, it is of considerable significance to analyze the flow hydrodynamics of wet particles in fluidized beds, which will improve the reactor design and process optimization. Thus, experimental and numerical investigations on wet particles in a bubbling fluidized bed are conducted in current work. On experimental side, particle image velocimetry (PIV) technology is employed with a designed bubbling fluidized bed. The silicone oil is used in this work because it is nonvolatile and transparent. On numerical side, a modified discrete element method (DEM) numerical method is developed by compositing an additional liquid‐bridge module into the traditional soft‐sphere interaction model. Most of the physical parameters are chosen to correspond to the experimental settings. Good agreements of particle velocity are found between the DEM simulation and PIV measurement. The performance of different liquid contents and superficial gas velocities are examined. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1970–1985, 2016

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In this study, wet particle flow behaviors were investigated in a spouted bed using numerical simulations and experiments. Effects of liquid contents and viscosities were investigated. For the experiment, instantaneous particle distribution and particle velocity distributions were explored. Liquid content and viscosity affected flow pattern together. Keeping increasing liquid content and viscosity, the flow pattern displayed flow instabilities, and the gas channel became curved. Numerical simulation results of time-averaged particle velocities agreed well with the experimental data. The regime map of domination forces is shown. Drag force has little effect on particle flow behaviors with liquid viscosity exceeding 10 mPa·s, and contact and liquid bridge forces were almost 50–50. Furthermore, effects of liquid content and viscosity on particle granular temperature and velocity were explored. The experimental and numerical simulation results might provide theoretical guidance for reactor design and further investigation on particle flow behaviors with cohesive liquid.