Performance of a variety of low Reynolds number turbulence models applied to mixed convection heat transfer to air flowing upwards in a vertical tube

2004 ◽  
Vol 218 (11) ◽  
pp. 1361-1372 ◽  
Author(s):  
W S Kim ◽  
J D Jackson ◽  
S He ◽  
J Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Low Reynolds Number ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Convection Heat ◽  
Mixed Convection Heat Transfer ◽  
Low Reynolds

The study reported here is concerned with mixed convection heat transfer to air flowing upwards in a vertical tube. Computational simulations of experiments from a recent investigation have been performed using an ‘in-house’ code which was written specifically for variable-property, developing, buoyancy-influenced flow and heat transfer in a vertical passage. The code incorporates a selection of two-equation, low Reynolds number turbulence models. The objective of the study was to evaluate the models in terms of their capability of reproducing the effects on turbulent heat transfer of non-uniformity of fluid properties and buoyancy. Direct comparisons have been made between results from the experimental investigation and those obtained by computational modelling for a range of conditions. The trends of impairment and enhancement of heat transfer owing to the influence of buoyancy found in the experiments were captured to some extent in the simulations using each of the models. However, none reproduced observed behaviour correctly over the entire range of buoyancy influence.

Numerical Study of Deteriorated Convection Heat Transfer of Supercritical Fluid Flowing Through Vertical Mini Tube at Relatively Low Reynolds Numbers

2018 ◽  
Author(s):  
Chen-Ru Zhao ◽  
Zhen Zhang ◽  
Qian-Feng Liu ◽  
Han-Liang Bo ◽  
Pei-Xue Jiang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Convection Heat ◽  
Flow Acceleration ◽  
Heat Transfer Deterioration ◽  
Low Reynolds

Numerical investigations are performed on the convection heat transfer of supercritical pressure fluid flowing through vertical mini tube with inner diameter of 0.27 mm and inlet Reynolds number of 1900 under various heat fluxes conditions using low Reynolds number k-ε turbulence models due to LB (Lam and Bremhorst), LS (Launder and Sharma) and V2F (v2-f). The predictions are compared with the corresponding experimentally measured values. The prediction ability of various low Reynolds number k-ε turbulence models under deteriorated heat transfer conditions induced by combinations of buoyancy and flow acceleration effects are evaluated. Results show that all the three models give fairly good predictions of local wall temperature variations in conditions with relatively high inlet Reynolds number. For cases with relatively low inlet Reynolds number, V2F model is able to capture the general trends of deteriorated heat transfer when the heat flux is relatively low. However, the LS and V2F models exaggerate the flow acceleration effect when the heat flux increases, while the LB model produces qualitative predictions, but further improvements are still needed for quantitative prediction. Based on the detailed flow and heat transfer information generated by simulation, a better understanding of the mechanism of heat transfer deterioration is obtained. Results show that the redistribution of flow field induced by the buoyancy and flow acceleration effects are main factors leading to the heat transfer deterioration.

Investigation of Temperature Uniformity in an Open Cavity of Buoyancy Assisted Mixed Convection Heat Transfer With Multiple Discrete Inlet and Outlet Ports

2014 ◽  
Author(s):  
G. Yang ◽  
J. Y. Wu ◽  
Y. W. He ◽  
L. Yan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temperature Gradient ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Open Cavity ◽  
Temperature Uniformity ◽  
Convection Heat ◽  
Grashof Number ◽  
Mixed Convection Heat Transfer

Turbulent buoyancy assisted mixed convection heat transfer in an open cavity with multiple discrete inlet and outlet ports is investigated experimentally. The side walls of the rectangular cavity are symmetrically heated with constant and uniform temperature. The temperature distribution in the interior of the cavity is presented and discussed for the Reynolds numbers of 3919 ≤ Re ≤ 35405, the Grashof numbers of 1.56 × 107 ≤ Gr ≤ 3.45 × 107, the Prandtl number of Pr = 0.71 and for various quantities of inlet and outlet ports ranging from 1 × 1 to 5 × 5 with the same total opening area. Increasing Reynolds number and decreasing Grashof number can improve the temperature uniformity in the cavity. As the dispersion of the inlet ports increases, the maximum temperature gradient of the fluids in the cavity is decreased while the average temperature gradient is increased. The effect of inlet/outlet forms, Reynolds number and Grashof number on the Nusselt number is also investigated.

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