FLOW ANALYSIS IN RECTANGULAR BAFFLED REACTOR HAVING DIFFERENTLY MODIFIED ANGLED BAFFLES USING ANSYS FLUENT

Abstract

Physical/ biochemical processes are designed for specific detention time. The control of detention time is not difficult in a batch reactor but in a continuous flow reactor, the flow distribution pattern makes it difficult to have flow through time matching with hydraulic detention time. In the recent past, the determination of flow through time could be done only through tracer studies and visualisation of flow patterns on physical models. The overall conclusions about the flow regimes in the reactors were deciphered through residence time distribution studies. Every modification of the reactors configuration required the construction of a modified physical model and maintenance of desired/ designed detention time. For efficiency of reactors, it is important to choose the L: B ratio appropriately further the volume of dead zone needs to be kept to a minimum. Effective detention time can also be enhanced through the use of baffles. In the present study, flow analysis of rectangular baffled reactor through differently modified hanging baffles is studied using computational fluid dynamics software. The geometry of reactor was designed in design modular (platform provided in ANSYS fluent) and simulated flow/velocity and fluid properties were input for the study of a different configuration of rectangular four compartments baffled reactor. Resulting flow patterns, flow regimes, velocity fields and dead spaces under varying conditions were analysed. Of the FOUR models, the 1st model reactor contains normal hanging angled baffle, 2nd model reactor contains baffles having 15 mm horizontal straightener, 3rd model having baffles having side steps like structure and 4th model contain straight baffles having 15 mm horizontal straightener. In each case flow pattern are considered and dead zones, velocity vector, turbulent kinetic energy, streamlines and velocity contours are analysed. Each model is made run with two different velocity magnitudes i.e. 0.07 cm/s and 0.14 cm/s hence the discharges are 10 litres per hour and 20 litres per hour. Different modifications are done on hanging baffles to minimise dead zones and short-circuiting. In model 1st and model 2nd streamlines and velocity vectors are observed in the maximum area of the reactor which means the effective volume of the reactor is utilised and hence an increase in efficiency of the reactor, also the up-flow velocity in these two reactors are within specific range. In final results, velocities at three different points in each chamber of reactors are obtained and graphs are plotted for each chamber. Observed results would be helpful in further future design improvement of the anaerobic Baffled reactor.