Almost 80% of the processes encountered in chemical process and allied industries are heterogeneous. A large spectrum of reactor configurations is available for multiphase contacting such as stirred reactors, bubble columns, spray columns, jet reactors, plate columns, fluidized beds, moving beds, etc. Almost all these reactors are operated in turbulent regime. Turbulent flows are studied using experimental and computational techniques.
University Institute of Chemical Technology (UICT) from its inception in 1934 is actively involved in solving the problems of the chemical industry related to chemistry and transport phenomena. To study the transport phenomena in detail, UICT has an excellent experimental facility for turbulence research and multiphase reactor design. The facility includes hot film anemometry, laser Doppler anemometry, ultrasound velocity profiler, particle image velocimetry and tomographic techniques. This facility is extensively used to study the flow patterns in different chemical reactors such as stirred vessels, jet reactors, bubble columns, packed and fluidized beds etc. The understanding of transport phenomena helps in improving the reliability in the design as well as energy saving.
However, experimentation over a wide range of geometric and operating conditions is not always possible. In such cases, computational fluid dynamics plays an important role. The experimental results help in validating the simulation results. For CFD simulation, our institute has both inhouse CFD codes plus ANSYS FLUENT and ANSYS CFX. CFD is used to study the mixing time, residence time distribution, turbulent kinetic energy and dissipation rate profiles, hold-up profiles, interfacial area and heat and mass transfer in the reactors.
One of the projects undertaken by our group is identification and characterization of flow structures and using the information in design and optimization of reactors. In this project, particle image velocimetry (PIV) and large eddy simulation (using ANSYS Fluent and ANSYS CFX) are carried out in channel flow, jet reactor, stirred vessels, bubble column, packed and fluidized beds. The transient velocity data over plane of interest were analyzed using advanced mathematical techniques such as Fourier and wavelet transformation and POD. The energy content distribution over different scales was obtained in all the geometries at different Reynolds numbers. Depending on application, the local dissipation rates can be manipulated by modifying the internals in the reactors for energy efficient performance and miniaturization. Other major projects involve application of CFD in mixer settler, studies of hydrodynamic cavitation which is applied for biological cell disruption, waste water treatment, ballast water treatment etc.
Apart from applied research using CFD, the institute is also training the undergraduate and postgraduate students in transport phenomena and computational fluid dynamics. At any point of time around 40 post students are working on problems involving computational fluid dynamics.
Large eddy simulation of stirred tank reactor using disk turbine. Trailing vortices are shown behind the
impeller blades. These vortices have a marked effect on the final performance of the reactor. The impeller's design is optimized
based on the understanding of fluid mechanics to reduce the excess energy dissipation close to impeller and homogenize it
throughout the vessel or dissipate it at the desired locations.
Hydrodynamic cavitation reactor
Cavitation generated hydrodynamically by passing liquid through the orifice plate is
studied. In addition to Cavitation model available in FLUENT, detailed cavity/ bubble
dynamics equations are incorporated through compiled UDF’s which are solved
conjunction with continuous phase. Velocity contours show flow of liquid through orifice
of different designs to optimize the cavitational yield in hydrodynamic cavitation reactor.