A. Venu Vinod

Mixing characteristics of binary mixtures in a spout-fluid bed

ABSTRACT Mixing characteristics of binary mixtures in a flat-bottom cylindrical spout-fluid bed using glass beads and air are reported in this work. Experiments were carried out to investigate the mixing characteristics for binary mixtures at three flow conditions, i.e., only spouting, only fluidization and spout-fluidization. The experiments were performed at different gas velocities, diameter ratios of binary mixtures and three different bed arrangements. Mixing index was determined for fluidized bed and static bed conditions. It was found that, in all cases, lowest-diameter ratio mixture gave good mixing index values. For all flow conditions, mixing index for large–small bed arrangement was increasing with time, whereas for small–large bed arrangement, the mixing index deteriorated with time. However, in both cases, the mixing index reached almost a constant value. For well-mixed bed arrangement and spout-fluidization flow condition, segregation and re-mixing were observed.

The Effective Thermal Conductivity of Water Based Nanofluids at Different Temperatures

Three types of Al2O3/water, CuO/water, and TiO2/water nanofluids were prepared by dispersing nanoparticles in water. A surfactant (cetyltrimethylammonium bromide (CTAB)) was used to improve the dispersion of nanoparticles and suppress the formation of particle clusters to obtain stable suspensions. The effective thermal conductivity was measured using a thermal property analyzer. The addition of a surfactant did not have any effect on the thermal conductivity. The effect of nanoparticle particle concentration (0.3, 0.6, 1, 1.5, and 2 wt. %) at four nanofluid temperatures (40, 45, 50, and 60°C) was investigated. Results indicated that the thermal conductivity increased with increases in particle concentration and temperature. Two models (linear and nonlinear) were developed to predict the thermal conductivity.

Stability and Dynamic Behaviour of a Fluidised Bed Bioreactor Treating Phenolic Effluent

Abstract Stability aspects and dynamic behaviour of a draft-tube fluidised bed bioreactor treating phenolic effluent from a coal carbonisation plant have been investigated in the present study. Experiments were carried out to study the biodegradation of phenolic wastewater using the microorganism Pseudomonas sp., immobilised on solid support particles. The dynamics of the reactor system were monitored at various experimental conditions viz., feed (substrate) flow rates and phenol concentrations in the feed. The draft tube fluidised bed bioreactor was assumed to operate in a completely backmix mode and a model to predict the outlet phenol concentration for given inlet and equipment parameters was developed. The model equations were solved using 4 th order Runge-Kutta technique. The predictions made by the dynamic model were compared with experimental findings and the agreement between the two was good. Stability of the reactor to input disturbances was examined and it was found to be stable.

CFD simulation model for mixing tank using multiple reference frame (MRF) impeller rotation

In this work, CFD simulations have been conducted to investigate flow behaviour of water in fully baffled stirred tank with Rushton turbine as impeller. The aim of the paper is to develop CFD model...

CFD Simulation of Heat Transfer Using Nanofluids in Microchannel Having Dimples and Protrusions

Microchannel heat sinks are highly efficient cooling devices in electronic field. In this study, heat transfer characteristics of CuO–H2O nanofluid flowing through a microchannel having dimples/protrusions, were investigated using CFD package FLUENT 15.0. A constant heat flux of 5 × 105 W/m2 was uniformly applied on all four walls. Nanofluid enters the microchannel at 300 K under fully developed flow conditions. SIMPLE (Semi Implicit Method for Pressure Linked Equations) algorithm was used in the solution procedure. A second-order upwind scheme was used to solve the momentum and energy equations. The dimples/protrusions are arranged on the wall of microchannel either in aligned or in staggered manner. 3-D numerical simulations were carried out at various Reynolds numbers (100, 300, 500, 700). The heat transfer characteristics were obtained for various geometries by varying inlet velocity (1.2–8.7 m/s) and volume fraction (0–4 %) of nanofluid. Wall temperature of microchannel was found to be lower for higher values of velocity and nanoparticle volume fraction, indicating better transfer of heat from wall to fluid. The enhancement in heat transfer was evaluated by a parameter known as thermal performance (TP) which is a function of Nusselt number (Nu), friction factor (f). Entropy generation rate was determined to find optimal geometry. It was found that microchannel with dimples and protrusions and 4 vol.% CuO nanofluid gave the maximum heat transfer enhancement.

Controllability of Distillation Sequences for the Separation of Ternary Mixture

The present work aims at finding the best distillation sequence in terms of control properties for the separation of a ternary mixture of n-pentane, n-hexane and n-heptane. The study has been carried out using ASPEN PLUS. The different sequences have been compared for regulatory problem (step change in feed concentration and feed flow rate) and servo problem (step change in product composition). PI controller has been used to control level and composition in the various configurations studied. Auto tuning of the controller has been carried out using relay feedback test. Ziegler–Nichols method was used to calculate controller gain (KI) and integral time (τI) of PI controller. Controller parameters have been fine tuned using these tuning maps.

Microfluidics of Nanodrug Delivery: Effect of Reynolds Number Ratio and Particle Size

In the present study dealing with nanodrug delivery, nanofluid flow in a microchannel is considered. The nanofluid considered is a solid (aluminum oxide) - liquid (water) mixture. A transient 3-D problem of controlled nanodrug delivery has been numerically solved. The study has been carried out using ANSYS CFX Version 11.0. The velocity profile and dimensionless nanodrug concentration profile for different Reynolds number ratios were obtained at different axial stations along the length of the microchannel (z = 0.5, 5, and 10mm). Effect of particle size on drug uniformity has been investigated.

Studies on Gas Holdup in a Draft Tube Fluidised-bed Bioreactor

Abstract Studies on gas holdup have been carried out in a draft tube gas-liquid-solid fluidised-bed bioreactor treating phenolic wastewater at different feed concentrations of phenol, feed flowrates and air flowrates. From the data obtained through a set of experimental runs, an empirical correlation was developed for the overall gas holdup using dimensional analysis. It was found that the gas holdup increases with the flow rate of air and decreases with increase in the flow rate of water. In the concentration range considered in the study the variation of feed concentration of phenol did not affect the gas holdup.

Microfluidics of Nanodrug Delivery at Different Angles of Drug Injection

Studies into methods of using microelectromechanical systems (MEMS) technology for medical and biological application have led to the development of several interesting devices such as microneedles, micropumps, and microreservoirs. Such microsystems featuring controlled transport process are important in laboratory testing of predecessors of implantable smart devices as well as analysis of pharmaceuticals and performing biomedical precision tasks. In the present study dealing with nanodrug delivery, nanofluid flow in a microchannel with various angles of drug injection is considered. The nanofluid is a solid-liquid mixture in which nonmetallic nanoparticles are suspended. A transient 3-D problem of controlled nanodrug delivery has been numerically solved. The velocity profile and dimensionless nanodrug concentration profile for different angles of drug injection were obtained at different axial stations along the length of the microchannel (z = 0.5, 5, and 10mm), with one particle diameter (10 nm) and one Reynolds number ratio (? = 1.69).