Research Papers: Natural and Mixed Convection

Experimental and Numerical Investigation on Natural Convection Heat Transfer of TiO2–Water Nanofluids in a Square Enclosure

[+] Author and Article Information
Yanwei Hu

e-mail: hywhit@foxmail.com

Yurong He

e-mail: rong@hit.edu.cn
School of Energy Science and Engineering,
Harbin Institute of Technology,
Harbin 150001, China

Shufu Wang

China Gas Turbine Establishment,
Sichuan 621703, China
School of Energy Science and Engineering,
Harbin Institute of Technology,
Harbin 150001, China
e-mail: wsf@our234.cn

Qizhi Wang

School of Energy and Power Engineering,
Xi'An JiaoTong University,
Xi'An 710049, China
School of Energy Science and Engineering,
Harbin Institute of Technology,
Harbin 150001, China
e-mail: qizhiwang1987@163.com

H. Inaki Schlaberg

North China Electric Power University,
Beijing 102206, China
e-mail: h.i.schlaberg@ieee.org

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 6, 2012; final manuscript received August 28, 2013; published online November 12, 2013. Assoc. Editor: Sujoy Kumar Saha.

J. Heat Transfer 136(2), 022502 (Nov 12, 2013) (8 pages) Paper No: HT-12-1485; doi: 10.1115/1.4025499 History: Received September 06, 2012; Revised August 28, 2013

An experimental and numerical investigation on natural convection heat transfer of TiO2–water nanofluids in a square enclosure was carried out for the present work. TiO2–water nanofluids with different nanoparticle mass fractions were prepared for the experiment and physical properties of the nanofluids including thermal conductivity and viscosity were measured. Results show that both thermal conductivity and viscosity increase when increasing the mass fraction of TiO2 nanoparticles. In addition, the thermal conductivity of nanofluids increases, while the viscosity of nanofluids decreases with increasing the temperature. Nusselt numbers under different Rayleigh numbers were obtained from experimental data. Experimental results show that natural convection heat transfer of nanofluids is no better than water and even worse when the Rayleigh number is low. Numerical studies are carried out by a Lattice Boltzmann model (LBM) coupling the density and the temperature distribution functions to simulate the convection heat transfer in the enclosure. The experimental and numerical results are compared with each other finding a good match in this investigation, and the results indicate that natural convection heat transfer of TiO2–water nanofluids is more sensitive to viscosity than to thermal conductivity.

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Fig. 1

TiO2–water nanofluids: (a) Initial samples and (b) 24 h later

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Fig. 2

Schematic diagram of the enclosure, side view

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Fig. 3

Experimental setup

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Fig. 4

Discrete velocity of the D2Q9 model

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Fig. 7

Thermal conductivities of TiO2–water nanofluids

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Fig. 8

Comparison of thermal conductivities between experiment and prediction

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Fig. 9

Shear stress changes of the nanofluid and water at 20 °C.

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Fig. 10

Viscosity changes with temperature (3.85 wt. % of TiO2)

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Fig. 11

Viscosity changes with mass fraction of TiO2 at 20 °C

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Fig. 12

Temperature contours and velocity vectors under different heat powers (3.85 wt. % of TiO2): (a) 14 W, (b) 20 W, (c) 30 W, and (d) 40 W

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Fig. 13

Temperature and velocities at Y/H = 0.5: (a) temperature and (b) velocity

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Fig. 14

Comparison between simulation and experiment

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Fig. 6

Physical model of the enclosure, side view

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Fig. 5

Nonequilibrium extrapolation scheme




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