Convective heat transfer enhancement in low Reynolds number flows with wavy walls

The goal of this study is to evaluate the computational fluid dynamic (CFD) predictions of friction factor and Nusselt number from six different low Reynolds number k–ε (LRKE) models namely Chang–Hsieh–Chen (CHC), Launder–Sharma (LS), Abid, Lam–Bremhorst (LB), Yang–Shih (YS), and Abe–Kondoh–Nagano (AKN) for various heat transfer enhancement applications. Standard and realizable k–ε (RKE) models with enhanced wall treatment (EWT) were also studied. CFD predictions of Nusselt number, Stanton number, and friction factor were compared with experimental data from literature. Various parameters such as effect of type of mesh element and grid resolution were also studied. It is recommended that a model, which predicts reasonably accurate values for both friction factor and Nusselt number, should be chosen over disparate models, which may predict either of these quantities more accurately. This is based on the performance evaluation criterion developed by Webb and Kim (2006, Principles of Enhanced Heat Transfer, 2nd ed., Taylor and Francis Group, pp. 1–72) for heat transfer enhancement. It was found that all LRKE models failed to predict friction factor and Nusselt number accurately (within 30%) for transverse rectangular ribs, whereas standard and RKE with EWT predicted friction factor and Nusselt number within 25%. Conversely, for transverse grooves, AKN, AKN/CHC, and LS (with modified constants) models accurately predicted (within 30%) both friction factor and Nusselt number for rectangular, circular, and trapezoidal grooves, respectively. In these cases, standard and RKE predictions were inaccurate and inconsistent. For longitudinal fins, Standard/RKE model, AKN, LS and Abid LRKE models gave the friction factor and Nusselt number predictions within 25%, with the AKN model being the most accurate.

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Improved Modeling of Turbulent Forced Convective Heat Transfer in Straight Ducts

Journal of Heat Transfer ◽

10.1115/1.2826038 ◽

1999 ◽

Vol 121 (3) ◽

pp. 712-719 ◽

Cited By ~ 5

Author(s):

M. Rokni ◽

B. Sunden

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Convective Heat Transfer ◽

Convective Heat ◽

Low Reynolds Number ◽

Eddy Diffusivity ◽

Numerical Approach ◽

Generalized Gradient ◽

Forced Convective Heat Transfer ◽

Low Reynolds

This investigation concerns numerical calculation of turbulent forced convective heat transfer and fluid flow in their fully developed state at low Reynolds number. The authors have developed a low Reynolds number version of the nonlinear k-ε model combined with the heat flux models of simple eddy diffusivity (SED), low Reynolds number version of generalized gradient diffusion hypothesis (GGDH), and wealth ∝ earning × time (WET) in general three-dimensional geometries. The numerical approach is based on the finite volume technique with a nonstaggered grid arrangement and the SIMPLEC algorithm. Results have been obtained with the nonlinear k-ε model, combined with the Lam-Bremhorst and the Abe-Kondoh-Nagano damping functions for low Reynolds numbers.

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Heat and Mass Transfer Caused by a Laminar Channel Flow Equipped With a Synthetic Jet Array

2010 14th International Heat Transfer Conference, Volume 5 ◽

10.1115/ihtc14-22686 ◽

2010 ◽

Cited By ~ 2

Author(s):

Zdeneˇk Tra´vni´cˇek ◽

Petra Dancˇova´ ◽

Jozef Kordik ◽

Toma´sˇ Vit ◽

Miroslav Pavelka

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Reynolds Number ◽

Heat Transfer Enhancement ◽

Channel Flow ◽

Heat Mass Transfer ◽

Low Reynolds Number ◽

Transfer Enhancement ◽

Laminar Channel Flow ◽

Low Reynolds

Low-Reynolds-number laminar channel flow is used in various heat/mass transfer applications, such as cooling and mixing. A low Reynolds number implies a low intensity of heat/mass transfer processes, since they rely only on the gradient diffusion. To enhance these processes, an active flow control by means of synthetic (zero-net-mass-flux) jets is proposed. This arrangement can be promising foremost in microscale. The present study is experimental in which a Reynolds number range of 200–500 is investigated. Measurement was performed mainly in air as the working fluid by means of hot-wire anemometry and the naphthalene sublimation technique. PIV experiments in water are also discussed. The experiments were performed in macroscale at the channel cross-section (20×100)mm and (40×200)mm in air and water, respectively. The results show that the low Reynolds number channel flow can be actuated by an array of synthetic jets, operating near the resonance frequency. The control effect of actuation and the heat transfer enhancement was quantified. The stagnation Nusselt number was enhanced by 10–30 times in comparison with the non-actuated channel flow. The results indicate that the present arrangement can be a useful tool for heat transfer enhancement in various applications, e.g., cooling and mixing.

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