A Comparative Study of Performance of Low Reynolds Number Turbulence Models for Various Heat Transfer Enhancement Simulations

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Ankit Tiwari ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Transfer Enhancement ◽  
Low Reynolds

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.

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

2010 ◽  
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.

scholarly journals Effect of Pin Diameter Degressive Gradient on Heat Transfer in a Microreactor with Non-Uniform Pin-Fin Array under Low Reynolds Number Conditions

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2702
Author(s):  
Miao Qian ◽  
Jie Li ◽  
Zhong Xiang ◽  
Chao Yan ◽  
Xudong Hu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Low Reynolds Number ◽  
Hydrodynamic Characteristics ◽  
Pin Fin ◽  
Low Reynolds ◽  
Pin Fin Array

To improve the efficiency of hydrogen-producing microreactors with non-uniform pin-fin array, the influence of the pin diameter degressive gradient of the non-uniform pin-fin array (NPFA) on heat transfer and pressure drop characteristics is analyzed in this study via numerical simulation under low Reynolds number conditions. Because correlations in prior studies cannot be used to predict the Nusselt number and pressure drop in the NPFA, new heat transfer and friction factor correlations are developed in this paper to account for the effect of the pin diameter degressive gradient, providing a method for the optimized design of the pin diameter degressive gradient for a microreactor with NPFA. The results show that the Nusselt number and friction factor under a low Reynolds number are quite sensitive to the pin diameter degressive gradient. Based on the new correlations, the exponents of the pin diameter degressive gradient for the friction factor and Nusselt number were 6.9 and 2.1, respectively, indicating the significant influence of the pin diameter degressive gradient on the thermal and hydrodynamic characteristics in the NPFA structure.

Low-Reynolds number heat transfer enhancement in sinusoidal channels

2007 ◽  
Vol 62 (3) ◽  
pp. 694-702 ◽  
Author(s):  
Nathan R. Rosaguti ◽  
David F. Fletcher ◽  
Brian S. Haynes
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Low Reynolds Number ◽  
Transfer Enhancement ◽  
Low Reynolds

scholarly journals Effect of the angle of attack of a rectangular wing on the heat transfer enhancement in channel flow at low Reynolds number

2017 ◽  
Vol 54 (5) ◽  
pp. 1441-1452 ◽  
Author(s):  
Assadour Khanjian ◽  
Charbel Habchi ◽  
Serge Russeil ◽  
Daniel Bougeard ◽  
Thierry Lemenand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Channel Flow ◽  
Low Reynolds Number ◽  
Angle Of Attack ◽  
Transfer Enhancement ◽  
Low Reynolds

scholarly journals Rayeilgh number effect on the turbulent heat transfer within a parallelepiped cavity

2011 ◽  
Vol 15 (suppl. 2) ◽  
pp. 341-356 ◽  
Author(s):  
Mohamed Aksouh ◽  
Amina Mataoui ◽  
Nassim Seghouani ◽  
Zoubida Haddad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Natural Convection ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Practical Applications ◽  
Low Reynolds

This purpose is about a three dimensional study of natural convection within cavities. This problem is receiving more and more research interest due to its practical applications in the engineering and the astrophysical research The turbulent natural convection of air in an enclosed tall cavity with high aspect ratio (AR=H/W=28.6) is examined numerically. Two cases of differential temperature have been considered between the lateral cavity plates corresponding, respectively, to the low and high Rayleigh numbers: Ra=8.6?105 and Ra=1.43?106 [1]. For these two cases, the flow is characterized by a turbulent low Reynolds number. This led us to improve the flow characteristics using two one point closure low-Reynolds number turbulence models: RNG k-e model and SST k-w model, derived from standard k-e model and standard k-w model, respectively. Both turbulence models have provided an excellent agreement with the experimental data. In order to choose the best model, the average Nusselt number is compared to the experiment and other numerical results. The vorticity components surfaces confirm that the flow can be considered two-dimensional with stretched vortex in the cavity core. Finally, a correlation between Nusselt number and Rayleigh number is obtained to predict the heat transfer characteristics.

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