Mixing Characteristics for the single and air-water two-phase flows in multichannel-based miniaturized fixed-bed devices

Investigation on the miniaturized multichannel-based fixed-bed devices to enhance the heat and mass transfer performance is the key focus in the present study. Residence time distribution (RTD) is one of the most critical parameters to characterize the device’s flow distribution. In the current context, the RTDs of a liquid tracer for the air-water two-phase concurrent flows across the multichannel-based miniaturized fixed-bed devices (consist of 11 number of same dimensional parallel channels) with the variable heights were measured by the conductivity measurements and represented by axial dispersion model (ADM). The stream-flow rates of the two phases varied within the range of 8.33 × 10-8 – 3.83 × 10-7 m3 s-1. The axial dispersion coefficients and the specific energy dissipation values were analyzed. The impacts of pressure loss and the geometry on the hydrodynamic characteristics and mixing properties were well expressed. Based on the experimental data, new correlations were proposed.

Fluidized bed hydrodynamic modeling of CO2 in syngas: Distorted RTD curves

Bubbles rising through fluidized beds at velocities several times superficial velocities contribute to solids backmixing. In micro-fluidized beds, the walls constrain bubble sizes and velocities. To evaluate gas-phase hydrodynamics and identify diffusional contributions to longitudinal dispersion, we injected a mixture of H2, CH4, CO, and CO2 (syngas) as a bolus into a fluidized bed of porous fluid catalytic cracking catalyst while a mass-spectrometer monitored the effluent gas concentrations at 2 Hz. The CH4, CO, and CO2 trailing RTD traces were elongated versus H2 demonstrating a chromatographic effect. An axial dispersion model accounted for 92% of the variance in the data but including diffusional resistance between the bulk gas and catalyst pores and adsorption explained 98.6% of the variability. At 300 °C, the CO2 tailing disappeared consistent with expectations in chromatography (no adsorption). H2 and He are poor gas-phase tracers at ambient temperature. We recommend measuring the RTD at operating conditions.

Kinetic and residence time distribution modelling of tubular electrochemical reactor: analysis of results using Taguchi method

Decolorization of dye waste water is performed using a Tubular Electrochemical Reactor. Stainless steel and oxide coated on titanium mesh acts as the cathode and anode respectively. Experiments were conducted in batch with recirculation mode. The effect of operating parameters such as current density, initial dye concentration, flow rate and supporting electrolyte concentration on decolorization of Acid red dye has been studied and the results were analysed using Taguchi Method. A Residence Time Distribution (RTD) study has been conducted in a Tubular electro chemical reactor and an axial dispersion model has been developed to determine percentage decolorization. The model results are compared with experimental results and it was found that the model satisfactorily matches with the experimental results with high correlation coefficient.

A new compartmental model for describing the mixing behaviour in a multi-transversal jet reactor

The axial dispersion model (ADM) and tank-in-series model (TiSM) are conventionally used for determining mixing performance of a reactor, which is generated by transverse jets in many engineering applications. The effect of transverse jets on the mixing performance is not well determined by the ADM and TiSM when the Reynolds number of the mainstream flow is higher than ∼104. In this study, this problem was solved by a dispersive compartmental model (DCM). The DCM was a modification of the conventional compartmental model by adding a dispersive nature of plug flow compartment. The results of a series of tracer studies showed that the experimental data were better matched by the DCM than by the conventional models. The effect of transverse jets on the mixing characteristics was significant when the experimental data were modelled by the DCM. The DCM could be used for practical reactors where the E-curve shows a single peak.