Gas-Liquid flows in stirred tank reactors (STR) are used in many significant industrial operations such as hydrogenation, absorption, stripping, oxidation, hydrogenation, ozonation, chlorination, fermentation, etc. Gas-Liquid STRs are expected to perform several functions such as mixing, dispersing gas into liquid, mass and heat transfer and reactions. Gas hold up distribution and various flow regimes are the key parameters affecting performance of gas-liquid STRs. Various techniques such as visual analysis, photography, light attenuation, optical probe method are used to understand gas holdup distribution within stirred tanks. Most of these techniques have some limitations with respect to measurement of gas hold up distribution. Electrical Resistance Tomography (ERT) is an upcoming technique for obtaining both qualitative and quantitative data on multiphase process units non-invasively and non-intrusively. In this work, an attempt was made to establish and validate the ERT technique for characterizing gas-liquid flows in a laboratory scale STR using the Rushton turbine (RT) impeller. ERT was used to study gas holdup and to identify flow regimes. The results were compared with the visual measurements as well as previously published correlations. The effect of gas flow rate, impeller speed on the mean gas holdup is discussed. The methodology and results presented in this work will be useful to effectively apply ERT for characterizing gas-liquid flows in stirred tanks.

The combine effect of nanoparticle and magnetic field on a micropolar fluid flow between two parallel coaxial porous plates with uniform blowing is investigated in this article. The two kinds of Nanoparticles, i.e. Copper Oxide (CuO) and Alumina (Al 2 O 3 ) are mixed with base fluid water to prepare the mixture of microplar nanofluid for the analysis of this problem. The convergence analysis of the numerical solutions is considered for large mesh size and high tolerance error. It is interesting to note that the skin friction coefficient at the lower plate increases with increasing the magnetic field for both CuO − water and Al 2 O 3 − water micro-polar nanofluid but it decreases with increases in volume fraction of nanoparticles in both the fluids. A novel result is found from this analysis that the rate of heat transfer at the lower plate increases with increasing the either magnetic parameter or micro-rotation parameter or the volume fraction of nanoparticles in the case of both fluids. The effects of magnetic field and micro-rotation parameter on the velocity, micro-rotation, temperature and concentration profiles are analyzed. The radial velocity profiles increase near the stagnation point but decreases near the plates by increasing the blowing parameter.

This paper presents numerical and CFD simulation of an Al2O3-water nanofluid turbulent flow in a circular pipe which has a 36 mm diameter with a constant heat flux at the pipe wall using ANSYS FLUENT 2020 R2. The turbulent flow under different Reynolds numbers, from Re = 10000 to 50000 was used to process the numerical experiments. Different concentrations of nanoparticles, ranging from 1% to 4%, were used. The results were computed utilizing the single-phase approach. The coefficient of transfer of heat of nanofluids is found to be greater than that of base liquid. Enhancement in transfer of heat is also observed with rising in volume concentration of particles.