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Proceedings ArticleDOI

Exergy Analysis of Nanofluids in Microchannel

TL;DR: In this paper, an exergy analysis for nanofluids in microchannels was carried out, where three concentrations of 0.25 vol, 0.5 vol, and 1vol% are chosen to observe the volume fraction effect.
Abstract: Present study carries out an exergy analysis for nanofluids in microchannels. For this, two microchannels with diameter of 218 μm and 303 μm are chosen due to availability of experimental data.. The alumina nanoparticles with 45 nm average size are dispersed in DI water. The stability of these nanofluids is controlled by their pH. Three concentrations of 0.25 vol%, 0.5 vol% and 1vol% are chosen to observe the volume fraction effect. For the entropy generation analysis Bejan equations for internal flow are used. The order of magnitude method was used to simplify the equations. Initially, the analysis is carried out with the standard correlations (Dittus-Boelter and Blasius equations) for tube flow for laminar region. Frictional and thermal entropy generation rate ratios were found comparable and neither of them can be neglected. The entropy generation rate ratio was above unity for 218 μm channel while, it was below unity for 303 μm channel. The prediction of entropy generation rate ratio was higher for experimental correlations compared to that of theoretical correlations. The entropy generation number was higher for 303 μm channel and more prone to change with concentration. The thermal part of entropy generation was the major part of total entropy generation for 303 μm channel. Also, the absolute entropy generation was higher for 303 μm channel compared to 218 μm channel.Copyright © 2011 by ASME
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Journal ArticleDOI
TL;DR: In this article, a critical review of thermodynamic optimum of microchannels based on entropy generation analysis is presented, using entropy generation as evaluation parameter of micro-channels, which is used in this paper.
Abstract: In this study, a critical review of thermodynamic optimum of microchannels based on entropy generation analysis is presented. Using entropy generation analysis as evaluation parameter of microchann...

56 citations


Cites background from "Exergy Analysis of Nanofluids in Mi..."

  • ...Entropy generation in microchannels in the presence of nanofluids Singh et al.12 provided a theoretical investigation of the entropy generation analysis due to flow and heat transfer in nanofluids....

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  • ...Employing certain nanofluids as coolants might further benefit the minimization of entropy generation in MCHSs. Singh et al.63 carried out an exergy analysis for nanofluids in microchannels....

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  • ...These four studies were done by Singh et al.,12 Li and Kleinstreuer,13 Mah et al.,14 and Shalchi-Tabrizi and Seyf.15 This article includes many studies on entropy generation in microchannels....

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  • ...Singh et al.(63) carried out an exergy analysis for nanofluids in microchannels....

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Journal ArticleDOI
TL;DR: A detailed review of the entropy generation due to the heat transfer and the fluid flow through different channels is presented in this paper, with or without the use of nanofluids.
Abstract: This work presents a detailed review of the entropy generation due to the heat transfer and the fluid flow through different channels. The earlier contribution of the researchers in the form of theoretical, numerical and experimental studies on the entropy generation in the conventional or microchannels, with or without disruption in the flow and with or without the use of nanofluids is reviewed. The brief discussion on the microchannels, disrupted microchannels, nanofluids and entropy generation is presented. Studies performed on the channel cross-sectional shapes and rib shapes for thermal performance optimisation are discussed in the paper. Nanoparticles such as Al2O3, Cu, CuO, Ag, SiO2, etc. have been used for preparing the nanofluids along with water, ethylene glycol, etc. as base fluids. Additionally, the effect of disruption in flow field on the entropy generation is also discussed. The disruptions in the form of ribs, cavities, vortex generators, etc. have been taken into account. It is hoped that this review article can provide a basis for further research on the irreversibility analysis of the nanofluid flowing through disrupted microchannels to improve the hydrodynamic and thermal performance of the system.

15 citations

Journal ArticleDOI
02 Apr 2018-Entropy
TL;DR: In this article, heat transfer and entropy generation characteristics of flows of multi-walled carbon nanotube-based nanofluids were investigated in horizontal minitubes with outer and inner diameters of ~1067 and ~889 µm, respectively.
Abstract: During the last decade, second law analysis via entropy generation has become important in terms of entropy generation minimization (EGM), thermal engineering system design, irreversibility, and energy saving. In this study, heat transfer and entropy generation characteristics of flows of multi-walled carbon nanotube-based nanofluids were investigated in horizontal minitubes with outer and inner diameters of ~1067 and ~889 µm, respectively. Carbon nanotubes (CNTs) with outer diameter of 10–20 nm and length of 1–2 µm were used for nanofluid preparation, and water was considered as the base fluid. The entropy generation based on the experimental data, a significant parameter in thermal design system, was examined for CNTs/water nanofluids. The change in the entropy generation was only seen at low mass fractions (0.25 wt.% and 0.5 wt.%). Moreover, to have more insight on the entropy generation of nanofluids based on the experimental data, a further analysis was performed on Al2O3 and TiO2 nanoparticles/water nanofluids from the experimental database of the previous study of the authors. The corresponding results disclosed a remarkable increase in the entropy generation rate when Al2O3 and TiO2 nanoparticles were added to the base fluid.

10 citations


Cites background from "Exergy Analysis of Nanofluids in Mi..."

  • ...[43] study is one of few scarce entropy generation studies based on experimental data for Al2O3 nanoparticles with the diameter of 45 nm dispersed in water and with volume fractions of 0....

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