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Heat and Mass Transfer

, Volume 54, Issue 8, pp 2295–2303 | Cite as

Enhancement of natural convection heat transfer in a square cavity using MWCNT/Water nanofluid: an experimental study

  • Pranit Satish Joshi
  • Arvind PattamattaEmail author
Original
  • 188 Downloads

Abstract

In recent times, convective heat transfer using nanofluids has been an active field of research. However experimental studies pertaining to buoyancy induced convective heat transfer using various nanofluid is relatively scarce. In the present study, a square enclosure of dimensions (40 × 40 × 200) mm is used as test section. Initially, Al2O3/Water nanofluid with volume percentage of 0.1%, 0.3%, 1% and 2% and Rayleigh numbers ranging from 7 × 105 to 1 × 107 are studied. These results are then compared with Ho et al. (Int J Therm Sci 49(8):1345–1353, 2010) experimental data. Nusselt number (Nu) is calculated based on the thermophysical properties that are measured in-house for the given conditions. Further, MWCNT/Water nanofluid with volume percentage 0.1%, 0.3% and 0.5% is formulated and are studied for various Rayleigh numbers. Comparison of Al2O3/Water and MWCNT/Water nanofluid have been made for different volume fractions and for various range of Rayleigh numbers. It is observed that MWCNT/Water nanofluid when compared with Al2O3/Water nanofluid yields higher values of the Nusselt number for a given volume fractions. All the existing experimental studies using particle based nanofluid concluded a deterioration in natural convective heat transfer. This study for the first time demonstrates an enhancement in natural convection using MWCNT/Water nanofluid. Such enhancement cannot be simply explained based only on the relative changes in the thermophysical properties. Factors such as percolation network in MWCNT/Water nanofluid which increases the heat transfer pathway between two walls and the role of slip mechanisms might be the possible reasons for the enhancement.

Nomenclature

A

Area of cross section of heater, m 2

cp

Specific heat, J/k g K

\(\overline h\)

Average convective heat transfer coefficient, W/m 2 K

I

Current, A

k

Thermal conductivity, W/m K

Nu

Nusselt number

\(\overline {Nu}\)

Average Nusselt number

Nunorm

Normalized Nusselt number (N u n o r m = N u n f /N u b f )

\(\overline {q^{\prime \prime }}\)

Average heat flux, W/m 2

Ra

Rayleigh number

T

Temperature, K

V

Voltage, V

W

Characteristic length of test cell, m

Greek letters

β

Coefficient of thermal expansion, 1/K

𝜖

Uncertainty in the measurement

μ

Dynamic viscosity, P a.s

ϕ

Volume fraction of nanoparticles

ρ

Density, k g/m 3

Subscripts

bf

Basefluid

c

Cold

corr

Correction in heat loss

h

Hot

loss

Heat loss

nf

Nanofluid

norm

Normalized

np

Nanoparticle

t

Total Heat loss

Notes

Acknowledgment

The Authors’ gratefully acknowledge Prof. Amitava Ghosh, Prof. S.K.Das and their students at the Mechanical engineering department, IIT Madras, Prof. Ramaprabhu and his students at the Department of Physics, IIT Madras and Prof. Abhijeet Deshpande and his students at the Department of Chemical engineering, IIT Madras, for allowing them to use the required facilities.

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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Heat Transfer and Thermal Power Laboratory, Department of Mechanical EngineeringIndian Institute of Technology MadrasChennaiIndia

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