Neelkanth Nirmalkar

Indian Institute of Technology Ropar | Indian Institute of Technology Punjab · Department of chemical engineering

The physio-chemical hydrodynamics and the solute transport around a translating dispersed drop are often multicomponent and multiphase systems. When such a dispersed droplet system is out of the thermodynamic equilibrium, steep momentum and concentration gradients are developed around the interface leading to rapid flow and solute transport. In bro...

Droplets may rebound/levitate when deposited over a hot substrate (beyond a critical temperature) due to the formation of a stable vapor microcushion between the droplet and the substrate. This is known as the Leidenfrost phenomenon. In this article, we experimentally allow droplets to impact the hot surface with a certain velocity, and the tempera...

Nanomembranes have received a wide range of applications in water treatment, gas separation, molecular and supramolecular separations. Nanopores offer the separation of the components even at nano- or picomolar concentrations. In addition, DNA translocation, DNA sequencing of nucleotides, single molecular analyses for biomedical nanoscopic devices...

This work investigates the melting and heat transfer characteristics from an isothermally heated circular cylinder placed inside twelve differentially shaped enclosures filled with the lauric acid (PCM). Extensive results are reported on streamlines, temperature contours, and rate of melting to delineate the influence of enclosure shape on the melt...

The ionic current rectification (ICR) is a non-linear current-voltage response upon switching the polarity of the potential across nanopore which is similar to the I–V response in the semiconductor diode. The ICR phenomenon finds several potential applications in micro/nano-fluidics (e.g., Bio-sensors and Lab-on-Chip applications). From a biologica...

Liquid-gas operation explores the widespread applications in multiple chemical processes industries. For an instance, the inclusion of fermentation, dissolved air flotation, paper and pulp processing, sludge decomposition, aeration, ozonation, etc. are majorly covered. Liquid-gas contacting devices are primarily employed to perform their mixing, an...

The combined effects of yield stress, shear-thinning, and shear-thickening fluid behaviour are investigated when a drop is falling in a Herschel-Bulkley fluid. The constitutive relation for Herschel-Bulkley fluids is regularized using the Papanastasiou regularization method. The governing partial differential equations for mass, momentum, and speci...

In this work, we have investigated the flow and mass transfer across spherical droplet falling in the non-Newtonian fluids (Casson fluids). For the different values of dimensionless parameters like Reynolds number; 1 Re 100 Bingham number; 0 Bn 50, viscosity ratio; 0.1 j 10; and Schmidt number ; Sc = 10. The governing equation of momentum and mass...

We have investigated the nanobubble generation, characterization, and their stability in monovalent and multivalent salt solution. The solubility of gases in aqueous salt solution decreases with salt concentration and this effect is the so-called “salting out effects” of dissolved gases. The dissolution of salt in water leads to dissociation of sal...

In the current work, the electroosmotic coupled pressure driven flow through a diverging microchannel has been numerically investigated for the simplified Phan Thien Tanner (PTT) fluids. The Debye-Hückel approximation is used for the linearization of electric potential distribution in the electric double layer and the Debye length has been kept fix...

Hydrodynamic cavitation is the recent advanced oxidation technique that finds applications in wastewater treatment, nanoparticle synthesis, mineral processing, sterilization, chemical synthesis. Owing to such overwhelming industrial applications, it has received a considerable attention in the recent past. Venturi and orifice geometries are linear...

In this work, we have investigated the flow and mass transfer across spherical droplet falling in the non-Newtonian fluids (Casson fluids). For the different values of dimensionless parameters like Reynolds number; 1≤Re≤100 Bingham number; 0≤Bn≤ 50, viscosity ratio; 0.1≤κ≤10, and Schmidt number; Sc = 10. The governing equation of momentum and mass...

Catalytic steam reforming (SR) of agricultural waste derived bio-oil for hydrogen production is a unique technology, offering twin benefits of waste management as well as sustainable energy production. In the present study, a series of LaNixCo1-xO3 perovskite catalysts (x= 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) were used for the steam reforming of sim...

In this work, we have answered this question by investigating the nano-entities nucleation during the salting-out effect. The solubility of gases in aqueous salt solution decreases with the salt concentration, and it is often termed as the”salting-out effects.” The dissolution of salt in water undergoes dissociation of salt and further solvation of...

The ionic current rectification (ICR) is a non-linear current-voltage response upon switching the polarity of the potential across nanopore, similar to the I-V response in the semiconductor diode. The ICR phenomenon finds several potential applications in micro/nano-fluidics (e.g., Bio-sensors and Lab-on-Chip applications). From a biological applic...

Hydrodynamic cavitation is a popular advanced oxidation technique and it has received wide range of applications from waste water treatment to the nanoparticles synthesis in recent years. The enhancement of the intensity of the hydrodynamic cavitation is always been an emerging field of research. Within this framework, we have proposed and investig...

Jet impingement configuration is commonly employed in the thermal management of the gas turbine engines, rocket launchers, and high-density electrical equipment cooling to remove a large amount of heat. Owing to such overwhelming applications, significant research efforts have been devoted to enhance the cooling performance of jet impingement confi...

Thermal energy storage in the phase change materials (PCMs) around a confined heated cylindrical heat source has been investigated numerically. This work aims to explore three major objectives namely; evolution of melting front around the cylindrical heat source, quantification of overall rate of heat transfer and identifying the factors to maximiz...

This work deals with the flow and mass transfer around a falling spherical drop in Bingham plastic fluids. Bubbles, drops, and particles are often dispersed in a suspending fluid of non-Newtonian nature. For example, suspensions of particles in a polymer solution are used in hydraulic fracturing slurries and swarms of bubbles are used in airlift bi...

Forced convection heat transfer in power-law fluids has been investigated numerically around four identical circular cylinders in a diamond array in a square enclosure. For the laminar flow, the governing equations have been solved numerically over the following ranges of parameters: Reynolds number (5 − 200), Prandtl number (0.7 − 100), power-law...

Extensive results are reported on the flow and heat transfer for Bingham plastic fluids for the same configuration as in Part I over the ranges: Reynolds number ( 5 − 200 ) , Prandtl number ( 1 − 100 ) , and Bingham number ( 0 . 01 − 100 ) and the gap ratio ( 0 . 3 − 0 . 7 ) . At small Bingham numbers, the results deviate a little from that in Newt...

In many situations, heat transfer occurs primarily by free convection, such as that in confined and restricted spaces and/or where it is not possible to induce fluid motion by using a pump or impeller. In this work, natural convection from an isothermal cone in power law and Bingham plastic fluids has been investigated numerically by solving the co...

We investigate the existence and stability of bulk nanobubbles in various aqueous organic solvent mixtures. Bulk nanobubble suspensions generated via acoustic cavitation are characterised in terms of their bubble size distribution, bubble number density and their zeta potential. We show that bulk nanobubbles exist in pure water, but do not exist in...

This paper elucidates parts of the mystery behind the interfacial and colloidal stability of the novel bubble system of bulk nanobubbles. Stable bulk nanobubble suspensions have been generated in pure water using hydrodynamic cavitation in a high-pressure microfluidic device. The effects of pH adjustment, addition of different types of surfactant m...

Bulk nanobubbles are a novel type of nanoscale bubble system. Because of their extraordinary behavior, however, their existence is not widely accepted. In this paper, we shed light on the hypothesis that bulk nanobubbles do exist, they are filled with gas, and they survive for long periods of time, challenging present theories. An acoustic cavitati...

A systematic numerical investigation on heat transfer from a heated sphere settling in aqueous nanofluids has been carried out to elucidate the effect of confinement and the other pertinent dimensionless numbers on heat transfer. In this work, four types of nanoparticles (NPs) have been considered, namely, Al2O3, CuO, SiO2 and ZnO, each of two diff...

In this work, the governing field equations describing the momentum and forced convection heat transfer from heated spheroids, including the limiting case of a sphere, in water based nanofluids have been solved numerically in the steady and axisymmetric flow regime over the following ranges of conditions: Reynolds number, ; nanoparticle volume frac...

In this work, the momentum and heat transfer characteristics of a heated sphere in tubes filled with Bingham plastic fluids have been studied. The governing differential equations (continuity, momentum and thermal energy) have been solved numerically over wide ranges of conditions as: Reynolds number, 1 ≤ Re ≤ 100; Prandtl number, 1 ≤ Pr ≤ 100; Bin...

Laminar natural convection from an isothermal sphere immersed in cold Bingham plastic media has been investigated numerically over wide ranges of the pertinent dimensionless parameters (Rayleigh number, 102 ≤ Ra ≤ 106; Prandtl number, 10 ≤ Pr ≤ 100; and Bingham number, 0 ≤ Bn ≤ 104). Extensive results on the flow and heat-transfer aspects are prese...

Most multiphase systems (emulsions, foams, suspensions, filled polymeric systems, for instance) encountered in wide ranging industrial applications often exhibit viscoplastic fluid behaviour in steady shear. Consequently, over the years, a voluminous body of knowledge has accrued on the fluid mechanical aspects of such viscoplastic fluids, albeit t...

In this work, the steady and laminar mixed-convection heat transfer from an isothermal sphere immersed in Bingham plastic fluids has been investigated in the aiding-buoyancy configuration. The pertinent coupled equations of motion and thermal energy have been solved numerically over the following ranges of conditions: Richardson number, 0 <= Ri <=...

The momentum and forced convection heat transfer characteristics of a heated equilateral triangular cylinder immersed in a Bingham plastic fluid have been studied numerically. The governing equations (continuity, momentum, and thermal energy) are solved for both vertex-upstream and vertex-downstream orientations, over wide ranges of the pertinent p...

In this work, mixed convective heat transfer from a heated square bar at an incidence of 45° in power-law fluids has been investigated numerically in the so-called aiding buoyancy configuration. The governing differential equations have been solved over the following ranges of conditions: Richardson number, 0 ≤ Ri ≤ 2, power-law index, 0.2 ≤ n ≤ 1,...

The present study deals with the prediction of drag and forced convection heat transfer behavior of a heated sphere in shear-thinning yield-stress fluids over wide ranges of conditions: plastic Reynolds number, 1 ≤ Re ≤ 100; Prandtl number, 1 ≤ Pr ≤ 100; Bingham number, 10–3 ≤ Bn ≤ 10; and shear-thinning index, 0.2 ≤ n ≤ 1. The momentum and energy...

In this work, momentum and heat transfer characteristics of a heated sphere immersed in visco-plastic media have been studied over a wide range of conditions: plastic Reynolds number, 1 ≤ Re ≤ 100, Prandtl number, 1 ≤ Pr ≤ 100, and Bingham number, 0 ≤ Bn ≤ 104. The equations of motion and energy have been solved numerically to elucidate the influen...

Heat transfer by laminar natural convection to Bingham plastic fluids from a heated horizontal circular cylinder in a square cavity has been investigated numerically. The governing partial differential equations describing the fluid flow and heat transfer have been solved (using the finite-element based COMSOL solver) over wide ranges of the pertin...

In this work, the steady, laminar, mixed convection heat transfer from a heated sphere immersed in power-law fluids has been investigated in the so-called aiding-buoyancy configuration. The momentum and thermal energy equations have been solved numerically over the following ranges of conditions: Richardson number, 0≤Ri≤20≤Ri≤2, power-law index, 0....

In this work, the momentum and heat transfer characteristics of a heated cylinder of square cross-section immersed in a streaming Bingham plastic medium have been studied. The governing differential equations (continuity, momentum and thermal energy) have been solved numerically over wide ranges of conditions as: plastic Reynolds number, 0.1⩽Re⩽400...

In this work, the influence of asymmetric confinement on momentum and heat transfer characteristics from a heated circular cylinder submerged in power-law liquids has been investigated numerically. The detailed flow and temperature fields are visualized in terms of the streamline and isotherm contours. Due to the asymmetry of the flow field, in add...