Vimal Kumar

Indian Institute of Technology Roorkee | University of Roorkee · Department of Chemical Engineering

The diversification of coal for its sustainable utilization in producing liquid transportation fuel is inevitable in countries with huge coal reserves. Gasification has been contemplated as one of the most promising thermochemical routes to convert coal into high-quality syngas, which can be utilized to produce liquid hydrocarbons through catalytic...

The present study deals with the numerical investigation of void fraction and flow patterns for liquid–liquid (oil–water) two-phase flow through a coiled flow inverter (CFI) with different flow conditions and geometrical orientations (horizontal and vertical). A CFI comprising 90° bends between two consecutive helical coils, and works on complete f...

The present study deals with numerical investigations of the boiling phenomena over a spherical surface at different degrees of superheat (ΔT), varying from 10 to 500 K. Various phenomena like vapor sliding, bubble formation, pinch‐off, induced vorticity have been illustrated for a deep understanding of the boiling process over a spherical surface....

In boiling phenomena, the heater surface gets covered by a vapor, which results in a decrease in the overall heat transfer coefficient (HTC). The curvature of the surface helps to reduce this vapor blanketing by vapor sliding over the curved surface. The sliding generates fluid circulation and makes the heater surface available for boiling liquid....

In the present study, the effect of simultaneous incorporation of SiC and WC additives on the densification behaviour and microstructural development of TiC-based composites is studied. Four different TiC-SiC-WC (TSW) composites with varying SiC and WC content were synthesized by ultrasonic wet milling followed by spark plasma sintering (SPS) at 17...

In the present work, the effect of batch high shear mixer (HSM) geometries is studied on nanoparticles deagglomeration and power draw in water and aqueous glycerol solutions. The kinetics and mechanism of cluster break-up are investigated for disintegrated (less number of larger stator holes), and mesh (higher number of smaller stator holes) heads...

High shear mixers (HSMs) find wide applications in industrial processes where intense mixing and dispersion of fluids play a vital role. In this work, the flow fields and mixing performance is analyzed in different batch HSMs with varying stator heads, such as disintegrated, slotted, and mesh. Further, the effect of viscosity, flow behavior and rot...

In the present work the products and characteristics of bio-yields obtained from pyrolysis of different types of walnut shells (WS) by using a fixed bed pyrolyzer. The different walnut shells considered are paper (PSW), thin (TSW), medium (MSW) and hard (HSW) shelled walnut. The biomass samples were pyrolyzed at various temperatures, particle sizes...

In the present work the products and characteristics of bio-yields obtained from pyrolysis of different types of walnut shells (WS) by using a fixed bed pyrolyzer. The different walnut shells considered are paper (PSW), thin (TSW), medium (MSW) and hard (HSW) shelled walnut. The biomass samples were pyrolyzed at various temperatures, particle sizes...

Dispersion of liquids/particles is a key important requirement in a variety of applications including coatings and paints, cosmetics, healthcare, food, and pharmaceutical processes. In all these industrial processes high intensity of energy is required to overcome the adhesion forces or increasing interfacial surface area per unit volume, which is...

A detailed understanding of chemical composition and thermal degradation behavior is very important for a biomass before processing it into a pyrolysis or gasification unit for energy production. In the present work, the physico-and thermo-chemical characterization of four different types of walnut shells (PSW, TSW, MSW and HSW) is carried out to e...

the hydrodynamics and thermal characteristics of nano-fluid, magnesium-oxide, in a spiral coiled-tube heat exchanger has been investigated numerically. Pure water and the nano-fluid with particle volume fraction of 0.0625%, 0.125%, 0.25%, 0.5% and 1% have been used as the fluid. Different cases with three different curvature ratios () of 0.02, 0.0...

With the rapid growth of pharmaceutical and biotechnology industry, stirred tank bioreactors have received much attention due to simple design, easy control of operating conditions, and low operating cost. In the development of commercial processes, however, a transition from laboratory to industrial scale faces great challenges because many proper...

The chemical equilibrium analysis of various possible reactions involved in the five CO2‐based routes for the synthesis of dimethyl carbonate (DMC), a green chemical reagent, was performed in the present study. The variation of the molar Gibbs free energy change with temperature for the major reactions of DMC synthesis in all five routes was studie...

Re-entry space vehicle necessities sharp leading edges for better aerodynamic performance and, hence, require advanced thermal protection materials with improved safety for crew members. Material possessing high thermal conductivity and oxidation resistance are desirable at nose cap and wings leading edge of spacecraft. Consequently, the thermal sh...

Biomass residues have potential to be used as an alternative solid fuel for various processes, also will be responsible for the optimization of the pyrolysis reaction processes, giving insight into the pyrolysis mechanisms and aiding in engineering efforts. There are different methods for production of bio-fuel from biomass residues; however before...

Breakage of nanoparticle cluster require high-intensity devices for stable and uniform distribution of aggregates. The ultra-sonication process is a high energy-intensive technique that produces cavitation effect to break the aggregates. In the present study, ultra-sonication is used for the de-agglomeration of fumed silica nanoparticles in low to...

In the present work, heat transfer and fluid flow characteristics for both Newtonian and non-Newtonian fluids in tube-in-tube helical coil (TTHC) heat exchangers have been investigated numerically. The various TTHC heat exchanger configurations studied are: 1) parallel flow with and without baffles, and 2) counterflow with and without baffles. The...

Present study deals with the newly investigated CEMNSE (combined energy mixed surfactant nanoemulsion) method for optimizing the operating parameters concerned with the formation of water-in-oil nanoemulsions (W/O NE). The formulation process was intensified by optimizing the operating parameters of CEMNSE methodby minimizing functions of two respo...

Stirred tank reactors (STRs) are most widely used in industrial applications including chemical, pharmaceutical and biological processes owing to their excellent operational flexibility and mixing capability [1,2]. Particularly in bioprocesses, they have attracted a great deal of attention due to their potential to integrate the development of high...

Essential oils from pine species have been utilized for numerous applications since centuries. This chapter discusses major aspects of pines’ essential oils, such as their composition, global availability, and medical as well as industrial applications. It has been observed that there are 40 major pine species with availability across the different...

Spiral-coiled tube heat exchangers (SCTHE) have higher heat transfer as compared to the conventional heat transfer devices and are extensively used to extract heat from exhaust gases in the chemical processing industries and also from sunlight for domestic applications. However, no attention has been made to predict heat transfer characteristics co...

Large eddy simulations (LES) have been carried out for the first time to characterize the flow and turbulent characteristics in three different batch high shear mixers (HSMs) at a constant rotor speed of 4000 rpm. Three HSMs having different stator heads such as circular, square and inclined stator head with 6, 92 and 210 numbers of stator holes, r...

1. Introduction The flow and mixing characteristics of particulate suspensions have long been the subject of academic interest. Particulate suspensions occur in industries such as food processing, polymer manufacturing, and pharmaceuticals. Rheological characterization of particulate suspensions is often conducted to better understand the complex v...

Global energy demand is increasing gradually because of increased economic growth or global GDP. According to US energy information report-2018, fuel consumption in year 2010 as 523 quadrillion Btu is expected to increases in year 2040 as 739 quadrillion Btu, a 28.84% increase. Moreover, use of fossil fuel is indispensable to cope up the need in sp...

Flowof oil-in-water (o/w) emulsions throughporousmediawas studied experimentally.Details of the theoretical developments of effective viscosity of emulsions flowing through unconsolidated porous media were presented. The emulsion rheological data were coupledwith the hydraulic radius concept and the Navier-Stokes (NS) equation to account for the pr...

Stirred tank reactors are most commonly used both in the laboratory and industry. Particularly for bioreactors, the volu-metric mass transfer coefficient (k L a) of oxygen is used as one of the important parameters for determining efficiencies of reactors and for successful scale-up. A number of correlation methods have been previously developed to...

The influence of emulsion pH and temperature on the rheological behavior of adhesive oil‐in‐water (o/w) emulsions stabilized with an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) was studied. The flow properties of emulsions as a complex fluid were investigated using steady and dynamic rheometry for characterization of non‐Newtonian b...

Mixing characterization of existing batch rotor-stator mixer (RSM) is studied at different rotor speeds (2000, 4000 and 6000 rpm) for two different geometries with different stator heads, such as circular and square. Flow parameters such as mass flow rate, Power number and energy dissipation rate have been investigated in both geometries.

A detailed understanding of chemical composition and thermal degradation behavior is very important for a biomass before processing it into a pyrolysis or gasification unit for energy production. In the present work, the physico- and thermo-chemical characterization of four different types of walnut shells (PSW, TSW, MSW and HSW) is carried out to...

Pyrolysis oil produced using lignocellulosic material is an alternate source of energy. Pyrolysis is an attractive option for the conversion of lignocellulosic biomass into liquid, pyrolysis oil, and gaseous hydrocarbons and is considered as an emerging and challenging research area in the current scenario of renewable energy. To ensure the product...

Diesel engines are used in heavy transportation vehicles and heavy machineries as they produce higher torque at low speeds for a given power meeting the primary requirement for a heavy engine. Moreover, diesel engines provide higher compression ratio and, if gasoline has to be used in bigger engines, they will produce higher knocking due to preigni...

Stirred tank reactors are most commonly used both in the laboratory and process industry to identify key factors that influence reactor performance. Particularly for bioreactors, the volumetric mass transfer coefficient (kLa) of oxygen is used as one of the important parameters for determining efficiencies of reactors and for successful scale-up. A...

In the present study hydrodynamics and mixing characteristics in a novel batch rotor-stator mixer (RSM), which is very simple in construction and design, is investigated at different rotor speeds (2000, 4000 and 6000 rpm). The proposed RSM design is comprised of tilted jets/holes in the stator, for the deep penetration in the mixing vessel. For the...

Formation of water-in-diesel oil (w/o) nano-emulsion has been achieved by low energy emulsification method by stabilizing a new combination of non-ionic sorbitan esters surfactants, i.e., PEG20-sorbitan mono-stearate and sorbitan mono-oleate in mixed proportions. Different combinations of the surfactants (T6 + S8) have been tested and best possible...

The electro-viscous effect on the stability and rheological behavior of oil-in-water (o/w) emulsions stabilized with an anionic surfactant (SDBS) has been studied by altering the emulsion pH. Emulsion pH was varied widely from 2-12 respectively. An increase in the pH of the emulsion led to an increase in emulsion stability, viscosity and viscoelast...

A 5-lump kinetic model is proposed and validated to mean the catalytic cracking of pyrolysis oils with equilibrium fluid catalytic cracking catalyst (E-CAT) in an advanced cracking evaluation (ACE-R) FCC unit. In the present work a blend of fast pyrolysis oil (FPO) with vacuum gas oil (VGO); hydrodeoxygenated oil (HDO) with VGO; and VGO are used as...

In the present work an ultarasonicator reactor is used to intensify the biodiesel production from vegetable in the presence of an alcohol and catalyst. The ultrasonicator parameters, such as amplitude ratio, recycle ratio and reaction time have been optimized for transesterification reaction. Refined soybean and crude jatropha oils were used as edi...

The numerical analysis of the mechanisms governing the flow in a porous region is of priority interest for modelling porous media flows. The present study describes an adapted and efficient turbulence modelling technique for this category of porous media flows. The main objective of the present study is to provide a detailed pore scale description...

In this work, experimental and statistical modeling and optimization of process parameters for maximizing the o/w emulsion stability was carried out using the multiobjective artificial neural network-genetic algorithm (ANN-GA) coupled with response surface methodology. The independent model constrains were oil concentration (10–50% v/v), surfactant...

In the present work, a mathematical and statistical approach was adopted to study the formation and stability of oil-in-water emulsion with an integrated hybrid genetic algorithm (GA) coupled with feed-forward back-propagation artificial neural network (BPANN) and response surface methodology (RSM) based on Box–Behnken design (BBD). The input param...

http://search.informit.com.au/documentSummary;dn=734199096436924;res=IELENG Oil-in-water (o/w) emulsions are ubiquitous in the petroleum refining operations where the water and oil content of the emulsion varies largely. In the present study the rheological behavior of o/w emulsions is studied to investigate the effects of temperature and volume f...

Oil-in-water (o/w) emulsions having different internal phase concentrations have been encountered in the petroleum industry during production, transportation and storage operations. The present study deals with the rheological behavior of o/w emulsions of varying internal phase (oil) concentrations (10–80%) at different temperatures (25–50 °C). A c...

Lignocellulosic biomass-derived fast pyrolysis oils are potential second-generation bio-fuels towards the reduction of greenhouse gas (GHG) emissions and carbon foot prints. This study pertains to co-process the Jatropha-derived heavy or tar fraction of fast pyrolysis oil (FPO) with vacuum gas oil (VGO) and hydrodeoxygenated fast pyrolysis oil (HDO...

Effective conversion of glycerol into fuels and chemicals is an emerging field in terms economic viability of first generation bio- fuels development. In the present work the refinery fluid catalytic cracking (FCC) process is used to convert the biomass -derived glycerol into possible fine chemicals through a series of reactions like dehydration, c...

The fluid catalytic cracking (FCC) route could be considered for the co-processing of biomass-derived pyrolysis oil with petroleum-derived vacuum gas oil (VGO) in a typical refinery unit by integrating it with a biomass fast pyrolysis process. This paper aims to study the effect of co-processing pyrolysis oil representative model compounds (C2–C3 c...

Turbulent flow through porous media is of considerable theoretical and practical interest in various engineering disciplines such as chemical, mechanical, nuclear, geological, environmental, petroleum, etc. In the present work, a numerical study of turbulent flow through porous media was carried out. The porous media was considered to be made of a...

Bio-diesel production through transesterification process involves reaction of the oil with alcohol in the presence of a catalyst resulting into the formation of a diesel equivalent bio-fuel. The present study deals with production of biodiesel from non-edible oil in the presence of co-solvents. A two-stage process was adopted for the production of...

Purpose The purpose of this paper is to investigate a large‐eddy simulation, using low order numerical discretization and upwinding schemes on unstructured grids, for a turbulent free jet at Mach number 0.95. The accuracy and stability performance is discussed for the finite element/volume upwinding numerical code used. Design/methodology/approach...

In the present work an attempt has been made to study the effect of catalyst-to-oil ratio (C/O) on the product distribution for the catalytic cracking of mixture of vacuum gas oil (VGO) with guaiacol and acetic acid, which are the representative model compounds of the biomass-derived fast pyrolysis oil. The catalytic cracking of mixture of VGO has...

Today’s an offshore platform costs billions of dollar to prepare and operate which is one of the costly affairs in the upstream oil sector. As the whole process has to deal with flammable fluids which are very risky and a small hazard in this can cause a big hazard to the industry in terms of money, human life, etc. This requires a detailed study o...

In the past few decades there has been an extensive increase in the research for green synthesis processes due to environmental concerns, industrial safety and sustainable development, which makes it an attractive alternative to the conventional synthesis processes. The interest of researchers in the green synthesis processes highlights the importa...

In the last decade there has been an exponential increase in microfluidic applications due to high surface-to-volume ratios and compactness of microscale devices, which makes them attractive alternatives to conventional systems. The continuing growing trends of microfluidic highlights the importance to understand the mechanism and fundamental diffe...

A low Reynolds number wind turbine is designed to extract the power from wind energy on Mars. As compared to solar cells, wind turbine systems have an advantage on Mars, as they can continuously produce power during dust storms and at night. The present work specifically addresses the design of a 500 W Darrieus-type straight-bladed vertical-axis wi...

In the present work, primarily two studies were carried out to ascertain the performance of coiled flow inverter (CFI) as heat exchanger at pilot plant scale. In the first study, performance of CFI heat exchanger has been compared with conventional heat exchangers, i.e. shell and tube heat exchanger (SHE) and plate type heat exchanger (PHE) under i...

A self-adaptive upwinding method for large eddy simulation (LES) has been describe in cross-flow in jets. The method is an extension of an existing Reynolds-averaged Navier–Stokes (RANS) code to an LES code by adjusting the contribution of the upwinding term to the convective flux. This adjustment is essentially controlled by reducing the upwind co...

In the present study a tube-in-tube helically coiled (TTHC) heat exchanger has been numerically modeled for fluid flow and heat transfer characteristics for different fluid flow rates in the inner as well as outer tube. The three-dimensional governing equations for mass, momentum and heat transfer have been solved using a control volume finite diff...

The present study deals with the numerical simulation of flow patterns and mixing behaviour in Kenics static mixer over a wide range of Reynolds number. Three different sets of Kenics mixer (aspect ratio=1.5) comprised of 3, 9 and 25 elements each have been characterized. The Reynolds number was varied in the range of 1 to 25,000 (i.e., from lamina...

The potential industrial applications of curved tubes for single- and two-phase flow are reviewed within the context of physics of flow, trends in the development of technology, and its laboratory to industrial-scale commercialization. Comparison of the performance of curved tube configurations demonstrates its edge over the conventional motionless...

The need for eco-friendly and energy saving processes which are substantially compact and give higher efficiency has led to the concept of process intensification (PI). Curved microchannel is such innovative device, which has potential for the intensification of processes currently carried out in conventional straight or T-type microchannels. Curve...

The convective heat transfer in chaotic configuration of circular cross-section under laminar flow regime at different values of Dean number and Prandtl number is investigated numerically. The chaotic configuration is the combination of 90° bends and coils. The insertion of equidistant 90° bends between the two consecutive coil produces the phenome...

In the present work attempts are made to investigate the hydrodynamics and heat-transfer characteristics of a coiled flow inverter (CFI) as heat exchanger at the pilot plant scale. The experiments are carried out in counter-current mode operation with hot fluid in the tube side and cold fluid in the shell side. Experimental study is made over a ran...

Helically coiled tubes find applications in various industrial processes like solar collectors, combustion systems, heat exchangers, and distillation processes because of their simple and effective means of enhancement in heat and mass transfer. Though extensive work is available in the literature on curved tubes, no study is available considering...

In the present work the investigation of gas and liquid slugs for Taylor flow in curved tubes has been carried out numerically using CFD. In case of curved tubes due to the curvature the flow is 3D, therefore 2D geometry can not be used to predict the slug flow development. The 3D models for curved tube with premixed feed is considered for the slug...

The mixing efficiency in a curved tube is a complex function of the Reynolds number, Schmidt number, curvature ratio and tube pitch, therefore, the relative effectiveness of a helical tube is quite complicated and challenging over a straight tube. A state of art review on mixing of two miscible liquids in curved tubes revealed that the mixing in co...

In the present work attempts were made to investigate the hydrodynamics and heat transfer characteristics of tube-in-tube helical heat exchanger at the pilot plant scale. The experiments were carried out in counter current mode operation with hot fluid in the tube side and cold fluid in the annulus area. The outer tube was fitted with semicircular...

Flatter velocity profiles and more uniform thermal environments are extremely desirous factors for improved performance in flow reactors and heat exchangers. One means of achieving it in laminar flow systems is to use mixers and flow inverters. In the present study a new device is introduced based on the flow inversion by changing the direction of...