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Effects of gravity and variable thermal properties on nanofluid convective heat transfer using connected and unconnected walls

Li, Qianqian; Wang, Jin LU ; Wang, Jiansheng; Baleta, Jakov; Min, Chunhua and Sundén, Bengt LU (2018) In Energy Conversion and Management 171. p.1440-1448
Abstract

In this paper, heat transfer characteristics of natural convection in an enclosure are investigated by considering variable thermal properties. The heated enclosure with an aspect ratio of unity is full of an alumina-water nanofluid. To analyze the effect of different thermal properties on the flow and temperature distributions, many comparisons are conducted for various cases at various Rayleigh numbers and volume fractions of nanoparticles (1–9.5%). The effect of low-gravity conditions on natural convection is investigated by using the gravity values of 0.25 g (2.45 m/s2), 0.5 g (4.9 m/s2), 0.75 g (7.35 m/s2) and 1.0 g (0.98 m/s2). It was found that larger temperature gradients near the... (More)

In this paper, heat transfer characteristics of natural convection in an enclosure are investigated by considering variable thermal properties. The heated enclosure with an aspect ratio of unity is full of an alumina-water nanofluid. To analyze the effect of different thermal properties on the flow and temperature distributions, many comparisons are conducted for various cases at various Rayleigh numbers and volume fractions of nanoparticles (1–9.5%). The effect of low-gravity conditions on natural convection is investigated by using the gravity values of 0.25 g (2.45 m/s2), 0.5 g (4.9 m/s2), 0.75 g (7.35 m/s2) and 1.0 g (0.98 m/s2). It was found that larger temperature gradients near the heated and cold walls can be obtained by increasing the Rayleigh number. By increasing the value of gravity, the flow velocity increased along the y direction. This indicated that gravity has great influence on enhancement of heat transfer. The investigation of the volume fraction of nanoparticles shows that the variation of the Nusselt number for high volume fraction presented a more flat profile than for low volume fraction. The Nusselt number decreased with an increase of the volume fraction. Results for cases with connected and unconnected heated walls are presented. The results showed that heat transfer for the case with the nanoparticle volume fraction of 1% at 1.0 g increased by 89.9% using an unconnected heated wall compared to the connected heated wall.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Enclosure, Gravity, Nanofluid, Natural convection, Thermal property
in
Energy Conversion and Management
volume
171
pages
9 pages
publisher
Elsevier
external identifiers
  • scopus:85049064824
ISSN
0196-8904
DOI
10.1016/j.enconman.2018.06.097
language
English
LU publication?
yes
id
47fa4c89-43ac-41ea-b2eb-3a3751d402d7
date added to LUP
2018-07-09 11:29:06
date last changed
2018-07-09 11:29:06
@article{47fa4c89-43ac-41ea-b2eb-3a3751d402d7,
  abstract     = {<p>In this paper, heat transfer characteristics of natural convection in an enclosure are investigated by considering variable thermal properties. The heated enclosure with an aspect ratio of unity is full of an alumina-water nanofluid. To analyze the effect of different thermal properties on the flow and temperature distributions, many comparisons are conducted for various cases at various Rayleigh numbers and volume fractions of nanoparticles (1–9.5%). The effect of low-gravity conditions on natural convection is investigated by using the gravity values of 0.25 g (2.45 m/s<sup>2</sup>), 0.5 g (4.9 m/s<sup>2</sup>), 0.75 g (7.35 m/s<sup>2</sup>) and 1.0 g (0.98 m/s<sup>2</sup>). It was found that larger temperature gradients near the heated and cold walls can be obtained by increasing the Rayleigh number. By increasing the value of gravity, the flow velocity increased along the y direction. This indicated that gravity has great influence on enhancement of heat transfer. The investigation of the volume fraction of nanoparticles shows that the variation of the Nusselt number for high volume fraction presented a more flat profile than for low volume fraction. The Nusselt number decreased with an increase of the volume fraction. Results for cases with connected and unconnected heated walls are presented. The results showed that heat transfer for the case with the nanoparticle volume fraction of 1% at 1.0 g increased by 89.9% using an unconnected heated wall compared to the connected heated wall.</p>},
  author       = {Li, Qianqian and Wang, Jin and Wang, Jiansheng and Baleta, Jakov and Min, Chunhua and Sundén, Bengt},
  issn         = {0196-8904},
  keyword      = {Enclosure,Gravity,Nanofluid,Natural convection,Thermal property},
  language     = {eng},
  month        = {09},
  pages        = {1440--1448},
  publisher    = {Elsevier},
  series       = {Energy Conversion and Management},
  title        = {Effects of gravity and variable thermal properties on nanofluid convective heat transfer using connected and unconnected walls},
  url          = {http://dx.doi.org/10.1016/j.enconman.2018.06.097},
  volume       = {171},
  year         = {2018},
}