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Technical Briefs

Natural Convection Heat Transfer Performance of Non-Newtonian Power-Law Fluids Enclosed in Cavity With Complex-Wavy Surfaces

[+] Author and Article Information
Ching-Chang Cho

Department of Greenergy,
National University of Tainan,
Tainan 700, Taiwan

Chieh-Li Chen

Department of Aeronautics and Astronautics,
National Cheng Kung University,
Tainan 70101, Taiwan

Jenn-Jiang Hwang

Department of Greenergy,
National University of Tainan,
Tainan 700, Taiwan

Cha'o-Kuang Chen

Department of Mechanical Engineering,
National Cheng Kung University,
Tainan 70101, Taiwan
e-mail: ckchen@mail.ncku.edu.tw

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received January 11, 2013; final manuscript received July 16, 2013; published online October 25, 2013. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 136(1), 014502 (Oct 25, 2013) (5 pages) Paper No: HT-13-1014; doi: 10.1115/1.4025134 History: Received January 11, 2013; Revised July 16, 2013

Numerical simulations are performed to investigate the natural convection heat transfer performance of non-Newtonian power-law fluids in a cavity bounded by wavy vertical walls with different temperatures and flat horizontal walls under adiabatic conditions. The results show that for Rayleigh numbers greater than 103, the mean Nusselt number has a significantly increase as the flow behavior index is decreased. Moreover, it is shown that in the convection-dominated regime, the mean Nusselt number increases with an increasing Rayleigh number, while in the conduction-dominated regime, the mean Nusselt number remains approximately constant. Finally, it is shown that for a given fluid, the heat transfer performance can be optimized via an appropriate tuning of the wavelength and amplitude of the wavy surface depending on the Rayleigh number.

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Figures

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Fig. 1

Schematic illustration of complex-wavy-wall cavity

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Fig. 2

Variation of mean Nusselt number with Rayleigh number as function of flow behavior index. Note that α1 = 0.5, α2 = 0.2, and λ = 2W.

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Fig. 3

Variation of local Nusselt number along hot-wavy-wall surface for different wavy surface wavelengths given Rayleigh numbers of (a) Ra = 1 × 103 and (b) Ra = 1 × 106. Note that n = 0.8, α1 = 0.5, and α2 = 0.2.

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Fig. 4

Variation of mean Nusselt number with wavy surface wavelength as a function of flow behavior index given Rayleigh numbers of (a) Ra = 1 × 103 and (b) Ra = 1 × 106. Note that α1 = 0.5 and α2 = 0.2.

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Fig. 5

Variation of local Nusselt number along hot-wavy-wall surface for different wavy surface amplitudes given Rayleigh numbers of (a) Ra = 1 × 103 and (b) Ra = 1 × 106. Note that n = 0.8 and λ = 4W.

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Fig. 6

Variation of mean Nusselt number with Rayleigh number as function of wavy surface amplitude given flow behavior indexes of (a) n = 0.8, (b) n = 1.0, and (c) n = 1.2. Note that λ = 4W in every case.

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