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Arvind Pattamatta
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Arvind Pattamatta
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Arvind Pattamatta
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Pattamatta, Arvind
Pattamattaa, Arvind
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17 results
Now showing 1 - 10 of 17
- PublicationScaling analysis for the investigation of slip mechanisms in nanofluids(01-12-2011)
;Savithiri, S.; The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it. © 2011 Fang et al. - PublicationEffect of flow maldistribution on the thermal performance of parallel microchannel cooling systems(01-01-2014)
;Manoj Siva, V.; This paper brings out the phenomenon of the influence of flow maldistribution on temperature distribution in parallel microchannel system that is supposed to have an adverse effect on hot spot formation in microelectronic devices. An extensive experimental study is carried out where in the parameters affecting the flow maldistribution such as channel hydraulic diameter, channel flow configurations (U, Z, I type) and chip power are varied to study their effect on the pressure drop and temperature distribution across the parallel channels designed for liquid cooling of a CPU using distilled water. It is observed that the flow distribution among the channels improves significantly with a decrease in the channel hydraulic diameter due to higher pressure drop offered by each individual channels simultaneously. This results in a considerable reduction in both the peak temperature and the average temperature of the device with decrease in channel diameter and better temperature distribution. It is observed that a higher pressure drop in d = 88 μm induces more uniform distribution compared to d = 176 μm resulting in a 3 C improvement in the standard deviation of temperature on the chip surface and a reduction in maximum surface temperature. Higher heat fluxes induce a reduction in viscosity of the fluid resulting in higher flow maldistribution. © 2014 Elsevier Ltd. All rights reserved. - PublicationA single-component nonhomogeneous lattice boltzmann model for natural convection in Al2O3/water nanofluid(17-11-2015)
;Savithiri, S.; Natural convection heat transfer in Al2O3/water nanofluid is analyzed using the single-component nonhomogeneous lattice Boltzmann method (SCNHLBM). There exists a contradictory observation between the numerical and experimental works in the literature with respect to the heat transfer of nanofluids in natural convection. Nanofluid is treated as a single component with nonhomogeneous particle distribution introduced by a concentration transport equation of nanoparticles by considering the Brownian and thermophoretic diffusions. The average Nusselt number is found to deteriorate with increasing nanoparticle volume fraction; thus the trend of the experimental results is captured using SCNHLBM. Addition of Brownian and thermophoretic diffusion results in additional thermal diffusion and hence reduces the convective transport of heat. The contribution of Brownian and thermophoretic diffusions in heat transfer deterioration is revealed. - PublicationPercolation network dynamicity and sheet dynamics governed viscous behavior of polydispersed graphene nanosheet suspensions(01-01-2013)
;Dhar, Purbarun ;Ansari, Mohammad Hasan Dad ;Gupta, Soujit Sen ;Siva, V. Manoj; ; The viscosity of polydispersed graphene nanosheet (5 nm-1.5 μm) suspensions (GNS) and its behavior with temperature and concentration have been experimentally determined. A physical mechanism for the enhanced viscosity over the base fluids has been proposed for the polydispersed GNSs. Experimental data reveal that enhancement of viscosity for GNSs lies in between those of carbon nanotube suspensions (CNTSs) and nano-alumina suspensions, indicating the hybrid mechanism of percolation (like CNTs) and Brownian motion-assisted sheet dynamics (like alumina particles). Sheet dynamics and percolation, along with a proposed percolation network dynamicity factor, have been used to determine a dimensionally consistent analytic model to accurately determine and explain the viscosity of polydispersed GNSs. The model also provides insight into the mechanisms of viscous behavior of different dilute nanoparticle suspensions. The model has been found to be in agreement with the GNS experimental data, and even for CNT (diameter 20 nm, length 10 lm) and nano-alumina (45 nm) suspensions. © Springer Science+Business Media 2013. - PublicationExperimental Assessment of the Thermo-Hydraulic Performance of Automobile Radiator with Metallic and Nonmetallic Nanofluids(04-02-2020)
;Akash, A. R. ;Abraham, Satyanand; The overall heat transfer of a cross flow heat exchanger can be enhanced by using the nanofluids as coolant, which finds application in reducing the size and weight of automobile radiator. However, improving the heat transfer using nanofluids can be accompanied by simultaneous variations in the required pumping power. This study experimentally evaluates the thermo-hydraulic performance of three nanofluids—metallic (copper, aluminum) and nonmetallic (multiwalled carbon nanotube (MWCNT))—as coolant for an automobile radiator by utilizing an in-house test rig. An enhancement in overall heat transfer coefficient can be observed with nanocoolants (nanofluid as coolant), compared to the de-ionized water at the same Reynolds number. The maximum enhancement in the overall heat transfer coefficient was observed to be 40, 29, and 25% for MWCNT, copper, and aluminum nanofluids, respectively. The thermal performance of coolants was also compared with the same pumping power criterion. The overall heat transfer coefficient of nanofluids were higher than basefluid at low pumping power range and the trend changes with increase in the pumping power. The present study shows that the heat transfer characteristics at the same Reynolds number as well as at the same pumping power needs to be considered for the selection of appropriate nanocoolant for automobile radiator application. - PublicationA numerical study of flow and temperature maldistribution in a parallel microchannel system for heat removal in microelectronic devices(03-10-2013)
;Siva, V. Manoj; A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However, in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a "U" type parallel microchannel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a response surface based surrogate approximation and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n=7, Ac/Ap=0.69, and Re=100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system. © 2013 by ASME. - PublicationBridging Thermal and Electrical Transport in Dielectric Nanostructure-Based Polar Colloids(01-09-2015)
;Dhar, Purbarun ;Sengupta, Soujit; Heat and charge transport characteristics of nanocolloids have been bridged from fundamental analysis. The relationship between the two transport phenomena in dielectric nanostructure-based polar colloids has been quantitatively presented. An extensional intuitive analogy to the Wiedemann-Franz law has been drawn. Derived from the fact that mobile electrons transport both heat and charge within metallic crystal structure, the analogy can be extended to nanocolloids, wherein the dispersed population act as the major transporter. The analogy allows modeling of the relationship between the two phenomena, and sheds more insight and conclusive evidence that nanoparticle traversal within the fluid domain is the main source of augmented transport phenomena exhibit by nanocolloids. Important factors, such as the thermal and dielectric responses of the nanocolloid can be quantified and bridged through the semianalytical formalism. The theoretical analysis has been validated against experimental data and variant scientific literature, and good accuracy has been observed. - PublicationThe role of percolation and sheet dynamics during heat conduction in poly-dispersed graphene nanofluids(22-04-2013)
;Dhar, Purbarun ;Sen Gupta, Soujit ;Chakraborty, Saikat; A thermal transport mechanism leading to the enhanced thermal conductivity of graphene nanofluids has been proposed. The graphene sheet size is postulated to be the key to the underlying mechanism. Based on a critical sheet size derived from Stokes-Einstein equation for the poly-dispersed nanofluid, sheet percolation and Brownian motion assisted sheet collisions are used to explain the heat conduction. A collision dependant dynamic conductivity considering Debye approximated volumetric specific heat due to phonon transport in graphene has been incorporated. The model has been found to be in good agreement with experimental data. © 2013 AIP Publishing LLC. - PublicationParticle–fluid interactivity reduces buoyancy-driven thermal transport in nanosuspensions: A multi-component Lattice Boltzmann approach(02-08-2016)
;Savithiri, S. ;Dhar, Purbarun; ABSTRACT: Severe contradictions exist between experimental observations and computational predictions regarding natural convective thermal transport in nanosuspensions. The approach treating nanosuspensions as homogeneous fluids in computations has been pinpointed as the major contributor to such contradictions. To fill the void, inter-particle and particle–fluid interactivities (slip mechanisms), in addition to effective thermophysical properties, have been incorporated within the present formulation. Through thorough scaling analysis, the dominant slip mechanisms have been identified. A Multi-Component Lattice Boltzmann Model (MCLBM) approach is proposed, wherein the suspension has been treated as a non-homogeneous twin component mixture with the governing slip mechanisms incorporated. The computations based on the mathematical model can accurately predict and quantify natural convection thermal transport in nanosuspensions. The role of slip mechanisms such as Brownian diffusion, thermophoresis, drag, Saffman lift, Magnus effect, particle rotation, and gravitational effects has been accurately described. A comprehensive study on the effects of Rayleigh number, particle size, and concentration revealed that the drag force experienced by the particles is primarily responsible for the reduction of natural convective thermal transport. In essence, the dominance of Stokesian mechanics in such thermofluidic systems is established in the present study. For the first time, as revealed though a thorough survey of the literature, a numerical formulation explains the contradictions observed, rectifies the approach, predicts accurately, and reveals the crucial mechanisms and physics of buoyancy-driven thermal transport in nanosuspensions. - PublicationTrimodal charge transport in polar liquid-based dilute nanoparticulate colloidal dispersions(01-10-2014)
;Dhar, Purbarun; Abstract: The dominant modes of charge transport in variant polar liquid-based nanoparticulate colloidal dispersions (dilute) have been theorized. Theories formulating electrical characteristics of colloids have often been found to over- or under-predict charge transport in dilute suspensions of nanoparticles in polar fluids owing to grossly different mechanistic behaviors of concentrated systems. Three major interacting modes with independent yet simultaneous existence have been proposed and found to be consistent with analyses of experimental data. Electric double layer (EDL) formation at nanoparticle–fluid interface-conjugated electrophoresis under the influence of the electric field has been determined as one important mode of charge transport. Nanoparticle polarization due to short-range field non-uniformity caused by the EDL with consequent particle motion due to inter-particle electrostatic interactions acts as another mode of transport. Coupled electro-thermal diffusion arising out of Brownian randomization in the presence of the electric field has been determined as the third dominant mode. An analytical model based on discrete interactions of the charged particle–fluid domains explains the various behavioral aspects of such dispersions, as observed and validated from detailed experimental analysis. The analysis is also predictive of the dominance and behavior of the three modes with important nanocolloidal parameters such as temperature and concentration.