Flow Characteristics in the Improved Impinging Stream Reactor by Means of Particle Image Velocimetry (PIV)

Abstract

The impinging Stream is a novel technique in enhancing heat and mass transfer. In the conventional impinging stream reactor (ISR), as the particles in that reactor are affected by the fluid resistance, the energy of the particles is rapidly decreased after the infiltration of the reverse flow, which leads to the effective mixing of the particles. In this paper, we design an improved impinging stream reactor (IISR) that has different fluid inlet velocity but same mean fluid inlet velocity in a period, which still belongs to definition of impinging stream. In the present study, the flow characteristics in the IISR are investigated using particle image velocimetry (PIV) and computational fluid dynamics. The effects of the fluid inlet velocity in the axisymmetric opposed jets are discussed for equal mean volumetric flow rates of the two jets. The impingement plane and the flow filed of the IISR are measured from captured images using the PIV technique. The two fluid inlet velocity with different sinusoidal variations are applied in the improved impinging stream. Besides, the experimental results show that the impingement plane is moving instantaneously with the two inlet velocity changing dynamically, which expands efficient active areas compared with the conventional impinging stream. Besides, computational fluid dynamics are used in combination with the discrete phase model (CFD-DPM) to predict the flow characteristics within the improved Impinging Stream. The simulation results show that impinging stream flow field can be divided into the inlet, the impact zone, the exit zone and the vortex area. At the same time, the impact zone and the impingement plane is also found to be moving The CFD-DPM results give predictions that are in better agreement with the flow filed pictured by the PIV technique. Because of the complexity of the liquid immersion impinging stream, it is difficult to study the trajectory of the particles in the flow field, so we use the numerical simulation to study the motion of the particles in the immersion IISR. Analysis shows the effective mixing region of the particles can be greatly increased, particles’ motion trajectory can be longer and the heat and mass transfer between the particles and the interphase can be further enhanced. Compared with the conventional ISR, the IISR has obvious advantages. The results point out this improved impinging Stream has a good application prospect in future engineering works.