Department Of Chemical Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

The evaporation of colloidal dispersions is an elegant and straightforward route to controlled self-assembly of particles on a solid surface. In particular, the evaporation of particle laden drops placed on solid substrates has received considerable attention for more than two decades. Such particle filled drops upon complete evaporation of the solvent leave behind a residue, commonly called particulate deposit pattern. In these patterns, typically, more particles accumulate at the edge compared to the interior, a feature observed when coffee drops evaporate. Consequently, such evaporative patterns are called coffee stains. In this article, the focus is on the evaporation of highly dilute suspension drops containing particles of larger diameters ranging from 3 to 10 μm drying on solid substrates. This helps us to investigate the combined role of gravity-driven settling of particles and capillary flow-driven particle transport on pattern formation in drying drops. In the highly dilute concentration limit, the evaporative patterns are found to show a transition, from a monolayer deposit that consists of a single layer of particles, to a multilayer deposit as a function of particle diameter and initial concentration of particles in the drying drop. Moreover, the spatial distribution of particles as well as the ordering of particles in the deposit patterns are found to be particle size dependent. It is also seen that the order-disorder transition, a feature associated with the organization of particles at the edge of the deposit, observed typically at moderate particle concentrations, disappears at the highly dilute concentrations considered here. The evaporation of drops containing particles of 10 μm diameter, where the effect of gravity on the particle becomes significant, leads to uniform deposition of particles, i.e, suppression of the coffee-stain effect and to the formation of two-dimensional percolating networks. © 2021 American Chemical Society.

World University root node

Department of Mechanical Engineering

Langmuir

Further Insights into Patterns from Drying Particle Laden Sessile Drops

High entropy alloys (HEAs) have drawn considerable attention owing to their unique properties such as high fracture toughness, good strength–ductility combination and enhanced corrosion resistance. In this study, the corrosion resistance dependence on the crystal structure and grain size of AlCoCrFeNi HEA is investigated. AlCoCrFeNi HEA with different mixture of body centered cubic (BCC) and face centered cubic (FCC) phases is produced using sequential alloying and tested for corrosion resistance in 3.5 wt% NaCl solution. CoNi+Fe+Cr+Al (84% BCC), FeCr+Ni+Al+Co (62% BCC) and AlNi+Co+Cr+Fe (38% BCC) alloy sequences have corrosion potential of −454, −299 and −524 mV (vs. SCE), and corrosion current of 14, 0.4 and 12 µA, respectively. FCC is a tight binding lattice with higher packing fraction than BCC which made it better for corrosion resistance, but FCC is rich in elements like Co, Ni, and Fe which are easily corroded. These two competing effects lead to a nearly optimum corrosion resistance for FeCr+Ni+Al+Co alloy sequence with 62% BCC and 32% FCC. It is also observed that an increase in grain size improves corrosion resistance. The influence of different chemical elements, crystal structure and microstructure (coarse vs. nanocrystalline) on corrosion resistance is discussed. © 2020 Elsevier B.V.

Department Of Civil Engineering

Journal of Alloys and Compounds

Effect of crystal structure and grain size on corrosion properties of AlCoCrFeNi high entropy alloy

Detailed studies on asphaltenes from Indian sources are scarce. In this study, nC7 asphaltenes were extracted from an atmospheric tower bottom and a low waxy crude oil using IP143-based method and characterised using elemental analysis, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, matrix-assisted laser desorption-time of flight mass spectroscopy, X-ray diffraction, and scanning electron microscopy. Results show that both asphaltenes differ widely in structures and molecular weights. It was deduced that both asphaltenes might have formed from kerogen degradation process resulting in higher oxygen content. Lower molecular weight and structural parameters (NMR) of atmospheric tower bottom asphaltene could be due to degradation of aliphatic part during preheating before atmospheric distillation process. Although dispersed, the XRD derived aromaticity of petroleum asphaltenes seems to vary inversely with stacking height and average diameter of the aromatic sheets, possibly due to compact structure of the cluster resulting from decreased stack height. Copyright © 2021 Inderscience Enterprises Ltd.

International Journal of Oil, Gas and Coal Technology

Chemical and structural characterisation of nC7 asphaltenes extracted from atmospheric tower bottom and low waxy crude oil from Indian reservoir

Surface modification of metallic Cu by conventional oxidation and an alternative method of oxidation using flame annealing and its influence on electrochemical reduction (ECR) of CO2 are reported in this study. The ECR of CO2 in aqueous KCl electrolyte yielded methane, ethane, ethylene, and hydrogen as the major products. The faradaic efficiency of ethane obtained at −1.2 V vs NHE for flame-annealed Cu (34 %) was comparable to the conventionally oxidised Cu (40 %), while bare Cu yielded methane (10 %). The metal–metal oxide interface on the electrode aids in the formation of C2-based products. Flame annealing can be regarded as an alternative electrode preparation method for C2 product formation, with its merits in high specific surface area, self-rejuvenating mode on deactivation and ease of preparation. © 2021 Wiley-VCH GmbH

ChemistrySelect

Electrochemical Reduction of CO2 on Flame Annealed Cu

Current work involves entropy generation studies within nine porous containers involving identical area for Prm = 155 (engine oil), (Formula presented.) at (Formula presented.) The entropy generation maps for lesser values of Dam depict that (Formula presented.) is dominant at the boundaries whereas (Formula presented.) is dominant at the central zone. On the other hand, for larger values of Dam, (Formula presented.) is found to be dominant throughout the porous containers. Zones corresponding to (Formula presented.) are found at the bottom corners of all porous containers due to the hot cold junction whereas zones corresponding to (Formula presented.) vary with the shapes of porous containers. An energy efficient process corresponds to larger (Formula presented.) larger (Formula presented.) and lesser Stotal. Containers with curved walls are found to be thermally efficient for thermal processing of engine oil saturated porous medium. © 2021 Taylor &amp; Francis Group, LLC.

Numerical Heat Transfer; Part A: Applications

Finite element-based evaluation on the role of various shaped containers (oil saturated porous media) for entropy generation versus heating efficiency involving thermal convection with identical heating

Process industries rely on effective decision-making by human operators to ensure safety. Control room operators acquire various inputs from the DCS, interpret them, make a prognosis, and respond through appropriate control actions. In order to perform these effectively, the operator needs to have appropriate mental models of the process. Poor mental models would increase the operator's cognitive workload and make them prone to errors. Traditionally, operator training systems are used to help operators learn appropriate mental models. However, performance assessment metrics used during training do not explicitly account for their cognitive workload while performing a task. In this work, we demonstrate that this leads to an incorrect assessment of operators’ abilities. We propose an Electroencephalography (EEG) power spectral density-based metric that can quantify the cognitive workload and provide detailed insight into the evolution of the operator's mental models during training. To demonstrate its utility, we have conducted training experiments with ten participants performing 438 tasks. Statistical studies reveal that the proposed metric can quantify the cognitive workload and therefore be used to assess operator training accurately. © 2021 Institution of Chemical Engineers

Department of Aerospace Engineering

Process Safety and Environmental Protection

Electroencephalography (EEG) based cognitive measures for evaluating the effectiveness of operator training

Purpose: The purpose of this paper is to address various works on mixed convection and proposes 10 unified models (Models 1–10) based on various thermal and kinematic conditions of the boundary walls, thermal conditions and/ or kinematics of objects embedded in the cavities and kinematics of external flow field through the ventilation ports. Experimental works on mixed convection have also been addressed. Design/methodology/approach: This review is based on 10 unified models on mixed convection within cavities. Models 1–5 involve mixed convection based on the movement of single or double walls subjected to various temperature boundary conditions. Model 6 elucidates mixed convection due to the movement of single or double walls of cavities containing discrete heaters at the stationary wall(s). Model 7A focuses mixed convection based on the movement of wall(s) for cavities containing stationary solid obstacles (hot or cold or adiabatic) whereas Model 7B elucidates mixed convection based on the rotation of solid cylinders (hot or conductive or adiabatic) within the cavities enclosed by stationary or moving wall(s). Model 8 is based on mixed convection due to the flow of air through ventilation ports of cavities (with or without adiabatic baffles) subjected to hot and adiabatic walls. Models 9 and 10 elucidate mixed convection due to flow of air through ventilation ports of cavities involving discrete heaters and/or solid obstacles (conductive or hot) at various locations within cavities. Findings: Mixed convection plays an important role for various processes based on convection pattern and heat transfer rate. An important dimensionless number, Richardson number (Ri) identifies various convection regimes (forced, mixed and natural convection). Generalized models also depict the role of “aiding” and “opposing” flow and combination of both on mixed convection processes. Aiding flow (interaction of buoyancy and inertial forces in the same direction) may result in the augmentation of the heat transfer rate whereas opposing flow (interaction of buoyancy and inertial forces in the opposite directions) may result in decrease of the heat transfer rate. Works involving fluid media, porous media and nanofluids (with magnetohydrodynamics) have been highlighted. Various numerical and experimental works on mixed convection have been elucidated. Flow and thermal maps associated with the heat transfer rate for a few representative cases of unified models [Models 1–10] have been elucidated involving specific dimensionless numbers. Originality/value: This review paper will provide guidelines for optimal design/operation involving mixed convection processing applications. © 2020, Emerald Publishing Limited.

International Journal of Numerical Methods for Heat and Fluid Flow

A comprehensive review on mixed convection for various patterns of kinematically and thermally induced scenarios within cavities

Blending water soluble synthetic polymers, such as polyvinyl alcohol (PVA), with natural polymers, such as pectin, has many advantages. However, due to the brittle nature of pectin, the mechanical properties become inferior in the blends. In this work, two strategies to enhance the toughness and tensile strength of solvent cast PVA/pectin blends are presented. This study shows that the tensile strength and toughness of PVA/pectin 80/20 blends can be enhanced by decreasing the solvent evaporation rate. The phase separation proceeds through 'nucleation and growth' and spinodal decomposition, respectively, at lower and higher rates of solvent evaporation. The equilibrium phase morphology has spherical domains of pectin dispersed in the PVA matrix. The size of the pectin domains and the separation between them are controlled by the solvent evaporation rate. At higher rates of solvent evaporation, pectin domains are larger and farther apart from each other and vice versa. Ionically crosslinking the pectin domains with calcium, further enhances the tensile strength and toughness of the blends compared to that of pure PVA. When the pectin domains are small, the failure happens at larger strains through 'cavitation' and 'shear yielding' and when pectin domains are large, the failure happens at smaller strains and the failure mechanism shifts to 'multiple crazing'. © 2020 Wiley Periodicals LLC.

Journal of Applied Polymer Science

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

A detailed molecular dynamics simulation study of the self-assembly, intermolecular structure and thermodynamic behavior of an aqueous solution of non-ionic surfactant octa ethylene glycoln-decyl ether (C10E8) in the presence of a non-ionic polar polymer poly(acrylic acid) PAA is presented. The aggregation numberNaggand concentration of surfactantCsin the simulation systems were varied in the range 0.01-0.32 M and 5 &lt;Nagg&lt; 101 (dilute to concentrated) with a dilute polymer concentration (Cp= 0.01 M). Lamellar aggregates of non-ionic surfactant in bulk aqueous solution are shown by molecular level computations for the first time. Spherical micellar aggregates and lamellar aggregates are formed at low and highNagg, respectively. The transition from the spherical micelle phase to the lamellar phase in a binary solution is captured for the first time. A conformational transition from coiled to extended PAA chains adsorbed on the surfactant aggregate occurs at a particular value ofNagg, commensurate with the transition from spherical micelle aggregates to anisotropic lamellar aggregates. Formation of the surfactant aggregate in binary and ternary solutions and the polymer-surfactant complex in a ternary solution is enthalpically favored. Adsorption of PAA on the surfactant aggregate surface is driven by hydrogen bonds (HBs) between carboxylic acid groups of PAA and ethylene oxide groups of C10E8. A significant number of HBs occur between polar oxygens of C10E8and hydroxyl oxygens of PAA. The results are in agreement with the limited available experimental data on this system. © The Royal Society of Chemistry 2020.

Fulltext

Soft Matter

Structure and dynamics of an aqueous solution containing poly-(acrylic acid) and non-ionic surfactant octaethylene glycoln-decyl ether (C10E8) aggregates and their complexes investigated by molecular dynamics simulations

Drilling fluids show significant role in the success of drilling operations of oil and gas well. Lubricating and rheological properties are important for efficient drilling leading to improved oil/gas production. The current work deals with assessing the lubricating properties of 16 different water-based drilling fluids using five lubricants and scrutinizing their consequence on the rheology of the mud, filtration properties and mud cake thickness. Experiments are carried out at 90 °C by hot rolling the drilling fluids. After aging, the rheological, API HPHT filtration loss, and lubricating properties of mud are measured at ambient conditions. The results have been discussed in relation to the effect of lubricants on the recovery performance of oil and gas from reservoir. Increased lubrication provides enhancement in rate of penetration, with improved drilling efficiency into the oil and gas reservoir rock formation. The HPHT filter press test showed permissible fluid loss for all the drilling fluid systems containing lubricants with thin and impermeable filter cake formation. The thin mud cake and less fluid loss into the reservoir indicate less reservoir damage while drilling thus indicating enhanced recovery of oil and gas during production operation. © 2021 Taylor & Francis Group, LLC.