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Article
Publication date: 26 February 2021

Subhasree Dutta, Somnath Bhattacharyya and Ioan Pop

The purpose of this study is to analyze the heat transfer and flow enhancement of an Al2O3-water nanofluid filling an inclined channel whose lower wall is embedded with…

Abstract

Purpose

The purpose of this study is to analyze the heat transfer and flow enhancement of an Al2O3-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch.

Design/methodology/approach

The mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number ( 103Gr5×104), nanoparticle bulk volume fraction ( 0.01φb0.05), nanoparticle diameter ( 30dp60) and the angle of inclination ( 60°σ60°).

Findings

The presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case.

Originality/value

This paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 14 July 2020

Subhasree Dutta, Somnath Bhattacharyya and Ioan Pop

This study aims to numerically analyse the impact of an inclined magnetic field and Joule heating on the conjugate heat transfer because of the mixed convection of an Al2O3

Abstract

Purpose

This study aims to numerically analyse the impact of an inclined magnetic field and Joule heating on the conjugate heat transfer because of the mixed convection of an Al2O3–water nanofluid in a thick wall enclosure.

Design/methodology/approach

A horizontal temperature gradient together with the shear-driven Flow creates the mixed convection inside the enclosure. The nonhomogeneous model, in which the nanoparticles have a slip velocity because of thermophoresis and Brownian diffusion, is adopted in the present study. The thermal performance is evaluated by determining the entropy generation, which includes the contribution because of magnetic field. A control volume method over a staggered grid arrangement is adopted to compute the governing equations.

Findings

The Lorentz force created by the applied magnetic field has an adverse effect on the flow and thermal field, and consequently, the heat transfer and entropy generation attenuate because of the presence of magnetic force. The Joule heating enhances the fluid temperature but attenuates the heat transfer. The impact of the magnetic field diminishes as the angle of inclination of the magnetic field is increased, and it manifests as the volume fraction of nanoparticles is increased. Addition of nanoparticles enhances both the heat transfer and entropy generation compared to the clear fluid with enhancement in entropy generation higher than the rate by which the heat transfer augments. The average Bejan number and mixing-cup temperature are evaluated to analyse the thermodynamic characteristics of the nanofluid.

Originality/value

This literature survey suggests that the impact of an inclined magnetic field and Joule heating on conjugate heat transfer based on a two-phase model has not been addressed before. The impact of the relative slip velocity of nanoparticles diminishes as the magnetic field becomes stronger.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 31 October 2018

Adrielle Borges de Almeida, Anna Karoline Carmo Silva, Ariadne Ribeiro Lodete, Mariana Buranelo Egea, Mayra Conceição Peixoto Martins Lima and Fabiano Guimarães Silva

The purpose of this study was to evaluate six different fruits from the Cerrado as to their chemical and bioactive properties.

Abstract

Purpose

The purpose of this study was to evaluate six different fruits from the Cerrado as to their chemical and bioactive properties.

Design/methodology/approach

Six different fruits from the Cerrado (araticum, baru, jatoba-do-cerrado, lobeira, macauba and pequi) were characterized regarding moisture, ash, lipids, proteins, carbohydrates, carotenoids, chlorophyll, ascorbic acid, flavonoids, phenolic compounds and their antioxidant activities.

Findings

The highest flavonoid content, which was found in araticum pulp, was significantly different from the ones of other fruit pulps. The carotenoid content of pequi pulp was 12-fold the one of lobeira pulp. The vitamin C content of baru pulp was five-fold the Reference Daily Intake (RDI). In relation to the antioxidant activity, araticum (5.7 µM/g) and jatoba (5.2 µM/g) pulps exhibited the highest values (p < 0.01). Both baru and araticum pulps were capable of capturing the radical with mean percentage of discoloration of 68.7 and 67.4%, respectively (p < 0.01).

Originality/value

Native fruits of the Cerrado have been poorly described in the literature, even though they are highly consumed in the region. Publicizing their nutritional characteristics can increase the commercial value of these fruits, which have been traditionally devalued. In addition, knowledge of new sources of nutrients contributes to their use by pharmaceutical and food industries.

Details

Nutrition & Food Science, vol. 49 no. 3
Type: Research Article
ISSN: 0034-6659

Keywords

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