Modelling and analysis of hydrodynamics and flow phenomena of fluid with formic acid as pollutant in the reactive area of a flat plate photocatalytic reactor with top and bottom turbulence promote

Abstract

The inadequate mixing of pollutant and its low mass transfer in the reactive surface reduces the efficiency of photocatalytic reactor. A computational model is developed, and numerical analysis is conducted to examine the effect of top and bottom baffles on the mass transfer and hydrodynamic performance of the reactor compared to reactor without baffle in this study. The hydrodynamic flow phenomena such as local streamlines, velocity, turbulence characteristic, pressure-drops, and wall shear stress were investigated. The experiment was done in a lab-scale flat-plate photocatalytic reactor using Formic Acid as pollutant in feed water for model validation. The FA concentration versus feed flow rate and velocity as a function of time showed good agreement between simulation and experimental results (only about 5 % variation). From the simulation, it was found that the pressure drops increase with increase in baffle height and the lowest was found to be 0.1 kPa and 0.4 kPa when the baffle height was 5 mm at velocity of 0.15 m/s and 0.5 m/s respectively. The highest turbulent kinetic energy and the dissipation was found 0.215 m2/s2 and 46 m2/s3 respectively when the baffle height was 12 mm in the present simulation. Baffles significantly changes the hydrodynamic performance such as turbulence, velocity, mass of pollutant and the pressure drops. The velocity magnitude also increases and the highest was found to be 9.2 times of the free stream velocity when 12 mm top baffle was used. Similar trends were found for bottom baffles. The highest magnitude of turbulent kinetic energy was found to be four times higher than the plain reactor without baffle. Therefore, baffle will significantly promote turbulence and improve the hydrodynamic performance thus enhance the photocatalytic rector performance.