Pradip Kumar Dutta

• Pradip Kumar Dutta at Motilal Nehru National Institute of Technology

Stand-alone microgrids, also known as remote area power supply systems, are crucial towards providing electricity access to off-the-grid locations/buildings and for communities trying to become 100% dependent on renewables. Design and development of efficient energy storage system remains a key challenge for the stand-alone microgrid technology. Me...

This paper investigates the performance of a canister module filled with phase change material (PCM) that is thermally coupled to an axially grooved heat pipe and designed for thermal management of unsteady or cyclic heat loads in spacecraft applications. The PCM canister stores heat from the electronic devices during brief transient peaks and slow...

Sorption-based thermal storage has drawn considerable attention for sustainable and cost-effective thermal management and energy storage. However, the low sorption capacity of sorbents is a long-standing challenge for achieving high-energy-density sorption-based thermal storage. Herein, we demonstrate an ultrahigh-energy/power-density sorption ther...

Heating and cooling systems based on hydrogen sorption in metallic alloys have attracted researchers due to their advantages such as environmental friendliness, ability to utilize low-grade waste or renewable energy, wide operating temperature ranges, and availability of a plethora of alloys to choose from. These heat-operated systems offer a viabl...

The present study reports development and application of a three dimensional phase field (PF) model, to investigate the microstructure evolution mechanism responsible for generation of spheroidal primary Al grains, associated with cooling slope processed semi solid slurry of A356 aluminium alloy. The cooling slope rheoprocessing technique involves...

The quest of automobile industries for weight reduction and enhancement of the mechanical strength of components has been a major incentive for new manufacturing technologies such as thixocasting. It is therefore important that the welded joints of such components exhibit adequate strength and formability. The present investigation is on optimizati...

Deprime in a loop heat pipe (LHP) is a phenomenon of drying out of capillary wick due to penetration of vapour into it. The vapour zone thickness increases with the LHP heat input due to the liquid-vapour interface recession into the wick away from the heating zone. An analytical model referred to as zero recession model is first presented to predi...

This chapter highlights the multiscale concentrated solar power thrust, which focused on developing new low-cost manufacturable technologies for both high- and moderate-temperature thermal cycles. In the high-temperature range, the focus was on the supercritical carbon dioxide (s-CO2) Brayton cycle. Research involved developing low-cost heliostats...

The cyclic performance of Mg2Ni alloy is analyzed in a thermal energy storage system at hydrogen supply and recovery pressures of 2 bar. Reaction rate equations for charging and discharging of Mg2Ni alloy are obtained by correlating the experimental data from literature. Simulation study is conducted on a 3D concentric tubular metal hydride reactor...

In this study, a computational fluid dynamics (CFD) model is developed to investigate die filling of semi solid slurry as part of rheo pressure die casting (RPDC) system. The die filling cavity corresponds to that of an automobile steering knuckle, and the slurry is made of A356 aluminium alloy. The rheological model used in the CFD simulation is d...

The goal of this paper is to experimentally study the thermal behavior of a miniature loop heat pipe (LHP) with flat evaporator and correlate the findings with visualization studies of the working fluid within the compensation chamber (CC). A miniature LHP with flat evaporator was fabricated and tested with four working fluids – acetone, methanol,...

Prior research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture...

In recent years with the advancement of nanotoxicology, the scientific communities drastically increased the investigation of the potential toxicity of nanominerals which are present in all atmospheres as well as are used in a variety of applications. In this study, we reported how Quartz Nanoparticles (QNPs) depending on concentration induces diff...

In the present paper, we present an experimentally validated 3D multiphase and multiscale solidification model to understand the transport processes involved during slurry generation with a cooling slope. In this process, superheated liquid alloy is poured at the top of the cooling slope and allowed to flow along the slope under the influence of gr...

This paper presents an in-depth numerical and thermodynamic study of a two-stage, 2-bed silica gel/water adsorption system for simultaneous generation of cooling power and potable water. The system is air cooled where the ambient temperature remains constant at 36 °C. The first part of this paper investigates the effect of cycle time, chilled water...

This paper presents a theoretical analysis of non-Newtonian (power-law obeying) fluid in a narrow confinement subjected to the combined consequences of interfacial electrokinetics, rheology, and superimposed magnetic field. We devote special attention on the exploitation of magnetic field and power-law exponent, in the development of induced stream...

Thermal energy storage at high temperature is a challenging research area with typical applications like regenerative heating in steel production plants and auxiliary energy source in solar thermal plants. Honeycomb structures made of ceramics are used as high temperature thermal energy storage units because of their large heat transfer surface are...

For concentrating solar power (CSP) plants to become cost competitive, it is necessary to design systems with significantly higher cycle efficiencies and to innovate cost-effective storage systems and materials. Higher cycle efficiency demands higher operating temperature, which implies that the optical system for the solar receiver needs to be des...

Adsorption systems can utilize low grade waste heat (temperature <100°C) or energy from renewable sources like solar for cogeneration i.e. cooling and desalination. The throughput and performance of such systems are sensitive to the available temperature difference between heat source and sink. This paper presents a modelling study of two-stage 2-b...

For the case of solidification of a bottom cooled binary alloy, the magnetohydrodynamic stationary and oscillatory convective stability in the mushy layer is investigated analytically using normal mode linear stability analysis. In the limit of large Stefan number (St), a near–eutectic approximation with large far field temperature is considered in...

Chitin-glucan complex (ChGC) was extracted from Agaricus bisporus (White Button Mushroom) biomass using a hot alkaline treatment for several times and washed with distilled water. The prepared material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Energy-dispersive...

Dynamic performance of a single-stage, two-bed, silica gel + water adsorption chiller operating in Bangalore, India is studied. Driving thermal energy is provided directly by an evacuated tube solar collector field. System dynamics are evaluated in the absence of thermal storage, which causes intra-day fluctuations in heat source and evaporator tem...

Elongated hydrogen porosity appears in aluminum based cast components and can lead to crack initiation. In this study, a comparison between the growth rates of hydrogen bubbles and the solidifying front during the process of engulfment is presented. Extending upon a previously developed order estimate for the ratio of growth rates of the two interf...

In this article, we investigate the combined consequences of magnetohydrodynamic forces and interfacial slip on the heat transfer characteristics of streaming potential mediated flow in narrow fluidic confinements by following a semianalytical formalism. Going beyond the celebrated Debye–Hückel linearization, we obtain a closed form analytical expr...

A phase field model is developed for simulation of microstructure evolution during semi solid slurry generation process of A356 aluminium alloy using a cooling slope. First, experiments are performed to evaluate the number of seeds required within the simulation domain to simulate near spherical microstructure formation, occurring during cooling sl...

A two-stage 4-bed/stage silica-gel + water adsorption system is developed for combined cooling and desalination, which adopts air cooled heat rejection obviating the disadvantages of cooling towers. Each stage has four adsorbers: three beds with identical design and one bed having a marginally different design. The present paper describes the desig...

The present work describes a silica gel+water adsorption-based desalination and chiller system, an emerging low cost process of integrating thermal desalination and cooling by utilizing low-grade heat. The cycle employs a combination of flash evaporation and thermal compression of steam in single/two stage to generate the dual effect. The current s...

A supercritical carbon dioxide (sCO2) Brayton cycle is an emerging high energy-density cycle undergoing extensive research due to the appealing thermo-physical properties of sCO2 and single phase operation. Development of a solar receiver capable of delivering sCO2 at 20 MPa and 700°C is required for implementation of the high efficiency (∼50%) sol...

Solar thermal power generation by and large uses Rankine cycles with organic working fluids or steam when highly concentrated solar source is used. Brayton cycle is seldom used because the work of compression forms a major fraction of turbine output. We investigate removal of this lacuna by adopting thermal compression using the adsorption route. H...

The present work explores the potential of semi-solid heat treatment technique by elucidating its effect on the plastic behavior of 304L SS in hot working domain. To accomplish this objective, hot isothermal compression tests on 304L SS specimens with semi-solid heat treatment and conventional annealing heat treatment have been carried out within a...

The supercritical carbon dioxide (S-CO2) based Brayton cycle is a good alternative to conventional power cycles because of high cycle efficiency, compact turbo machinery and compact heat exchangers. In this cycle, the majority of heat transfer (approximately 60-70% of total cycle heat transfer) occurs in the regenerator. For the regenerator, micro-...

A semi-solid processed steel with well arranged delta-ferrite layer around the austenite-solid globules is found to show different dynamic recrystallization (DRX) pattern compared to its conventionally processed counterpart with ferrite stringers across the austenite grains. Analysis of experimental results indicates that the presence of delta-ferr...

Brayton power cycles using high temperature, high pressure supercritical carbon dioxide (s-CO2) as the working fluid have been increasingly considered as attractive candidates for solar-thermal power plants. Several configurations of heat exchangers and solar receivers are under investigation, with predicted tube temperatures ∼1000 K. The inclusion...

Single phase performance and appealing thermo-physical properties make supercritical carbon dioxide (s-CO2) a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ∼973 K is required in order to merge CSP and s-CO2 Brayton cycle tec...

Thermal energy storage systems based on metal/hydrides usually are closed systems composed of two beds of metal/alloy – one meant for energy storage and the other for hydrogen storage. It can be shown that a feasible operating cycle for such a system using a pair of metals/alloys operating between specified temperature values can be ensured if the...

In the present work, microstructure evolution during semi-solid slurry generation of Al-Si-Cu-Fe alloy, using a cooling slope, was studied and the effect of microstructural morphology of the slurry on its rheological behavior was investigated. Microstructure evolution during melt flow along the slope was studied by extracting samples from various l...

This paper presents the instrumentation and control architecture for a laboratory based two-stage 4-bed silica gel + water adsorption system. The system consists of primarily two fluids: refrigerant (water vapour) and heat transfer fluid (water) flowing through various components. Heat input to the system is simulated using multiple heaters and amb...

The present study describes about the preparation of semisolid metal (SSM) slurry by using an oblique plate. In this process, A356 aluminum alloy melt partially solidifies while flowing over a bottom cooled oblique plate. Melt flow inertia shears columnar dendrites formed on plate wall into equiaxed/fragmented grains by resulting semisolid slurry a...

In this work, we present a numerical study of flow of shear thinning viscoelastic fluids in rectangular lid driven cavities for a wide range of aspect ratios (depth to width ratio) varying from 1/16 to 4. In particular, the effect of elasticity, inertia, model parameters and polymer concentration on flow features in rectangular driven cavity has be...

The compatibility of Beauveria bassiana (Bals.-Criv.) Vuill. with Chromolaena odorata (L.) King & H. Rob. (Asteraceae) was evaluated in vitro. Aqueous and solvent extracts of leaves of C. odorata at concentrations of 0.1, 0.5 and 1% were evaluated on the growth, conidial density and germination of B. bassiana by using the poisoned food technique. T...

In vitro compatibility of Nomuraea rileyi (farlow) was studied with six commonly used pesticides in vegetable ecosystem by poison food technique at recommended dose (rd) and half of recommended dose (1/2RD). The results were expressed in percent mycelial growth inhibition of N. rileyi colony on the insecticide treated medium. At field recommended d...

In vitro compatibility of Nomuraea rileyi (farlow) was studied with six commonly used pesticides in vegetable ecosystem by poison food technique at recommended dose (RD) and half of recommended dose (1/2RD). The results were expressed in percent mycelial growth inhibition of N. rileyi colony on the insecticide treated medium. At field recommended d...

The present work discusses the findings obtained from simulations of semi solid die filling of a steering knuckle, prior to actual component development using in-house developed rheo pressure die casting system. Die filling capability of A356 Al alloy at semi-solid state has been investigated using commercial software Flow-3Dcast to optimise the po...

The present work highlights the role of globular microstructure on the workability of A356 aluminum alloy at elevated temperature. The hot deformation behavior was studied by isothermal hot compression tests in the temperature range 573 K to 773 K (300 °C to 500 °C) and strain rate range of 0.001 to 10 s−1. The flow stress data obtained from the te...

The first objective of this paper is to show that a single-stage adsorption based cooling-cum-desalination system cannot be used if air cooled heat rejection is used under tropical conditions. This objective is achieved by operating a silica gel + water adsorption chiller first in a single-stage mode and then in a 2-stage mode with 2 beds/stage in...

In recent years, semisolid manufacturing has emerged as an attractive option for near net shape forming of components with aluminum alloys. In this class of processes, the key to success lies mainly in the understanding of rheological behavior of the semi-solid slurry in the temperature range between liquidus and solidus. The present study focuses...

Molten A356 aluminum alloy flowing on an oblique plate is water cooled from underneath. The melt partially solidifies on plate wall with continuous formation of columnar dendrites. These dendrites are continuously sheared off into equiaxed/fragmented grains and carried away with the melt by producing semisolid slurry collected at plate exit. Melt p...

Phase-change cooling technique is a suitable method for thermal management of electronic equipment subjected to transient or cyclic heat loads. The thermal performance of a phase-change based heat sink under cyclic heat load depends on several design parameters, namely, applied heat flux, cooling heat transfer coefficient, thermophysical properties...

High temperature, high pressure transcritical condensing CO2 cycle (TC-CO2) is compared with transcritical steam (TC-steam) cycle. Performance indicators such as thermal efficiency, volumetric flow rates and entropy generation are used to analyze the power cycle wherein, irreversibilities in turbo-machinery and heat exchangers are taken into accoun...

Desalination is one of the most traditional processes to generate potable water. With the rise in demand for potable water and paucity of fresh water resources, this process has gained special importance. Conventional thermal desalination processes involves evaporative methods such as multi-stage flash and solar distils, which are found to be energ...

RF MEMS devices like switches are made up of movable fragile structures that need to be encapsulated in microcavities to protect them from contamination or damage during the subsequent wafer dicing and packaging process steps. This packaging method is referred to as wafer-level or zero- level packaging and enables the whole MEMS wafer to be package...

This paper presents a theoretical model for studying the effects of shrinkage induced flow on the growth rate of binary alloy dendrites. An equivalent undercooling of the melt is defined in terms of ratio of the phase densities to represent the change in dendrite growth rate due to variation in solutal and thermal transport resulting from shrinkage...

The removal efficiencies of fluoride by nano and bulk material of activated charcoal, silica gel and rice husk were studied with four different fluoride concentrations viz 5.8, 6.5, 7.7 and 8.6 ppm. It has been observed that the removal efficiency of fluoride by bulk activated charcoal after 1h was found to be 55.1, 50.7, 46.7 and 40.5 percent for...

The present work presents the results of experimental investigation of semi-solid rheocasting of A356 Al alloy using a cooling slope. The experiments have been carried out following Taguchi method of parameter design (orthogonal array of L-9 experiments). Four key process variables (slope angle, pouring temperature, wall temperature, and length of...

A phase field modelling approach is implemented in the present study towards simulation of microstructure evolution during cooling slope semi solid slurry generation process of A380 Aluminium alloy. First, experiments are performed to evaluate the number of seeds required within the simulation domain to simulate near spherical microstructure format...

The microstructure of an austenitic SS 304L rapidly quenched from its semi-solid state shows a unique annular austenitic ring in between the core of each globule and its ferritic outer layer. On the basis of experimental results and microstructural analysis, it is proposed that the ring is formed as a result of preferential austenitic phase nucleat...

This paper highlights the role of globular microstructure on the weldability of semi-solid processed aluminum alloys via high temperature flow behavior. The investigation was carried out on the joining of thixocast A356 aluminum alloy components by friction welding. A thermomechanical model was developed to predict the temperature and stress distri...

This study is aimed toward obtaining near spherical microstructural features of Rheocast A380 aluminum alloy. Cooling slope (CS) technique has been used to generate semisolid slurry from the superheated alloy melt. Spherodization of primary grains is the heart of semisolid processing which improves mechanical properties significantly in the parts c...

This paper presents a new micro-scale model for solidification of eutectic alloys. The model is based on the enthalpy method and simulates the growth of adjacent α and β phases from a melt of eutectic composition in a two-dimensional Eulerian framework. The evolution of the two phases is obtained from the solution of volume averaged energy and spec...

This work presents an experimental investigation on the rheology of A356 alloy in semisolid state using a high temperature Couette type viscometer. The molten liquid, resides in the annular space between the cylinders, is stirred and cooled continuously during experiments. The stirring results in fragmentation of dendrites which are transported int...

While organic Rankine cycles have been widely used for power generation using low grade thermal energy, Brayton cycles have not been considered feasible because the work required to compress the gas nearly compensates the turbine work output. However, if the low grade energy can be used for thermal compression of the working fluid, it may be possib...

The paper presents a simulation study of loose cylindrically shaped particles packed within a copper plate and aluminum fins. The model presented solves coupled heat and mass transfer equations using the finite volume method based on ANSY S FLUENT medium. Three different arrangements of cylindrical particles are considered. The model is validated w...

Biocontrol offers solutions to many serious problems of modern agriculture and is one of the essential components of sustainable agriculture. Biocontrol agents are sensitive to the agrochemicals and gives erratic field results. Tolerance to agrochemical in the biocontrol agents can be enhanced through genetic manipulation. In the present study thre...

A theoretical analysis is carried out to observe the influence of important flow parameters such as Nusselt number and Sherwood number on the tip speed of an equiaxed dendrite growing in a convecting alloy melt. The effect of thermal and solutal transfer at the interface due to convection is equated to an undercooling of the melt, and an expression...

Purpose – In the present work, a numerical method, based on the well established enthalpy technique, is developed to simulate the growth of binary alloy equiaxed dendrites in presence of melt convection. The paper aims to discuss these issues. Design/methodology/approach – The principle of volume-averaging is used to formulate the governing equati...

In this article, we study the thermal performance of phase-change material (PCM)-based heat sinks under cyclic heat load and subjected to melt convection. Plate fin type heat sinks made of aluminum and filled with PCM are considered in this study. The heat sink is heated from the bottom. For a prescribed value of heat flux, design of such a heat si...

In this study, we present a new computational approach for studying the effect of melt convection on solidification at the micro-scale level. Models for den-dritic and eutectic growth are developed on the basis of the enthalpy technique and incorporate the pres-ence of flow in the domain. Simulation results show the growth and motion of dendrites a...

Lifetime measurements have been carried out for high spin states in 123Cs and 124Ba using the Doppler shift attenuation method. The transition quadrupole moments Qt measured in the present work show a loss of collectivity after the alignment of neutron h11/2 orbitals. The experimental results are compared with the existing theoretical calculations...

Formation of freckles during directional solidification of hypereutectic aqueous ammonium-chloride in a bottom cooled cavity is studied numerically. The system studied is thermally stable but solutally unstable, which causes plume type convection and formation of channels in the growing solid mush. Solidification of hypereutectic solutions is usual...

The main theme of this paper is to study the flammability suppression of hydrocarbons by blending with carbon dioxide, and to evaluate these mixtures as possible working fluids in organic Rankine cycle for medium temperature concentrated solar power applications. The analysis takes into account inevitable irreversibilities in the turbine, the pump,...

The adverse effects of HIV/AIDS not only impacts the infected or affected clients, but also affects the self-efficacy of HIV/AIDS counsellors. The study based on the experiences of 330 HIV/AIDS counsellors of western India (Maharashtra, Gujarat and Goa) finds that counsellors are comparatively much comfortable in dealing with clients from the gener...

Low grade thermal energy from sources such as solar, geothermal and industrial waste heat in the temperature range of 380–425 K can be converted to electrical energy with reasonable efficiency using isopentane and R-245fa. While the former is flammable and the latter has considerable global warming potential, their mixture in 0.7/0.3 mole fraction...

The paper discusses the effect of semi-solid processing on the microstructural evolution and mechanical property of 304L stainless steel. For the study, steel specimens were part ially melted and cooled to room temperatures in different cooling mediu m. The effect of temperature, t ime and cooling mediu m on microstructural evolution was studied by...

The three indicators of isentropic lines, namely, the isentropic index, the ratio of pressure and density p/ρ and the derivative (∂p/∂ρ)s are investigated for all of the fluids in the RefProp 9.0 program. The behaviour of these three entities is evaluated along the saturated vapour line as well as in the superheated vapour region. There is a distin...

In the present work, a cooling channel is employed to produce semi-solid A356 alloy slurry. To understand the transport process involved, a 3D non-isothermal, multiphase volume averaging model has been developed for simulation of the semi-solid slurry generation process in the cooling channel. For simulation purpose, the three phases considered are...

Rheological behavior of semi-solid slurries forms the backbone of semi-solid processing of metallic alloys. In particular, the effects of several process and metallurgical parameters such as shear rate, shear time, temperature, rest time and size, distribution and morphology of the primary phase on the viscosity of the slurry needs in-depth charact...

A new coupled approach is presented for modeling the hydrogen bubble evolution and engulfment during an aluminum alloy solidification process in a micro-scale domain. An explicit enthalpy scheme is used to model the solidification process which is coupled with a level-set method for tracking the hydrogen bubble evolution. The volume averaging techn...

Among all methods of metal alloy slurry preparation, the cooling slope method is the simplest in terms of design and process control. The method involves pouring of the melt from top, down an oblique and channel shaped plate cooled from bottom by counter flowing water. The melt, while flowing down, partially solidifies and forms columnar dendrites...

In the present work, the evolution of microstructure during solidification of A356 alloy under stirring is performed experimentally in a high temperature concentric viscometer. The stirring during solidification results a semisolid slurry in the annular space between the cylinders. This slurry is removed periodically during processing using a vacuu...

Present trend of semi-solid processing is directed towards rheocasting route which allows manufacturing of near-net-shape cast components directly from the prepared semi-solid slurry. Generation of globular equi-axed grains during solidification of rheocast components, compared to the columnar dendritic structure of conventional casting routes, fac...