Experimental Investigation of the Heat Transfer Characteristics of Aluminum-Foam Heat Sinks With Restricted Flow Outlet

2007 ◽  
Vol 129 (11) ◽  
pp. 1554-1563 ◽  
Author(s):  
W. H. Shih ◽  
F. C. Chou ◽  
W. H. Hsieh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Generation ◽  
Aluminum Foam ◽  
Heat Sinks ◽  
Pore Density ◽  
Heat Transfer Characteristics ◽  
Measured Velocity ◽  
Transfer Characteristics ◽  
Convective Resistance

This study investigates the heat transfer characteristics of aluminum-foam heat sinks with restricted flow outlets under impinging-jet flow conditions. An annular flow-restricting mask is used to control the height of the flow outlet of the aluminum foam sink, forcing the cooling air to reach the heat-generation surface. The enhanced heat transfer characteristics of aluminum-foam heat sinks using these flow-restricting masks are measured experimentally in this work. The effects of porosity, pore density and length of sample, air velocity, and flow outlet height on the heat transfer characteristics of aluminum-foam heat sinks are investigated. Results show that the effect of the flow outlet height is stronger than that of the pore density, porosity, or height of the aluminum heat sinks studied in this work. A general correlation between the Nusselt number and the Reynolds number based on the equivalent spherical diameter of the aluminum foam is obtained for 32 samples of aluminum-foam heat sinks with different sample heights (20–40mm), pore densities (5–40ppi(pore∕inch)), porosities (0.87–0.96), and flow outlet heights (5–40mm). It should be noted that, based on the measured velocity profile, the increase of the Nusselt number of the aluminum-foam heat sink with the decrease in the flow outlet height is caused by the reduced convective resistance at the solid-gas interface through the increased velocity near the heat-generation surface. The reduction in flow outlet height increases the local thermal nonequilibrium condition near the heat-generation surface.

Thermal Optimal Design for Heat Sinks or Heat Sink/TEC Assemblies in a Ducted Flow

2007 ◽  
Author(s):  
T. Y. Wu ◽  
M. C. Wu ◽  
J. T. Horng ◽  
S. F. Chang ◽  
P. L. Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Optimal Design ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Heat Sinks ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Starting Point

A series of experimental studies on the heat transfer characteristics from heat sinks or Heat Sink/TEC assemblies in a ducted flow have been performed. Their effects on heat transfer characteristics in ducted flow have been systematically explored. From the results, new performance correlations of the temperature difference (ΔT) and terminal voltage (V) of the TEC modules are proposed. Besides, two new correlations of steady-state average Nusselt number and external thermal resistance in terms of relevant influencing parameters for confined ppf heat sinks in a ducted flow are also proposed, respectively. The statistical sensitivity analysis of ANOVA F-test is employed to estimate the contributions of relevant parameters. Furthermore, a series of RSM models for evaluating heat transfer characteristics including average Nusselt number, average external thermal resistance and Tc−Ta are established. A Sequential Quadratic Programming with multi-starting-point method is successfully employed to automatically and efficiently seek a globally optimal thermal performance. An optimal design of HS/TEC assemblies under both COP ≥ 2 and pumping power limitation larger than 30 W can be achieved with a reduction of 75% on thermal resistance.

Pressure Drop and Heat Transfer Characteristics for Partially-Confined Heat Sinks in Ducted Flow

2006 ◽  
Author(s):  
H. T. Chen ◽  
T. Y. Wu ◽  
P. L. Chen ◽  
S. F. Chang ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Sink ◽  
Average Nusselt Number ◽  
Heat Sinks ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Effective Friction

The pressure drop and heat transfer characteristics for partially-confined heat sinks with different fin types, including plain-plate fin, pin-fin array and strip-fin array, in ducted flow are investigated. The main focus of the experimental results is on pressure drop and heat transfer characteristics of generalized heat sink in ducted flow with considering the flow top- and side-bypass effects. The parameters controlled in the study are the heating load (Qt), inlet flow velocity (Ui), the ratio of heat sink height to duct height (Hs/Hc), and the ratio of heat sink width to duct width (Ws/Wc). The ranges of parameters studied are Ui=2~12m/s, Qt=10~30W, Ws/Wc = 0.6~1, and Hs/Hc = 0.5~1. In the present study, an effective friction factor related to the overall pressure drop is defined; and a new experimental correlation for the effective friction factor for generalized heat sinks in ducted flow with top- and side-bypass effects is presented. A satisfactory agreement between the experimental data and the theoretical predictions is achieved with the maximum and average deviations of 17.2% and 9.6%, respectively. As for convective heat transfer performance, the average Nusselt number is not significantly affected by Grashof number; while, it increases significantly with increasing Reynolds number. Furthermore, the thermal performance increases with increasing top or side confinement ratio (Hs/Hc or Ws/Wc). The best thermal performance occurred at the fully-confined condition, i.e., Hs/Hc=1, Ws/Wc = 1. Based on all the experimental data for three types of partially-confined heat sinks, a generalized correlation of average Nusselt number for partially-confined heat sinks in ducted flow in terms of Re, Hs/Hc and Ws/Wc is presented. The maximum and average deviations of the results obtained by the experimental data from the theoretical prediction are 12.4% and 7.5%, respectively.

scholarly journals Uncertainties Analysis on the Prediction of Flow and Heat Transfer of Liquid Sodium with CFD Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhanwei Liu ◽  
Xinyu Li ◽  
Tenglong Cong ◽  
Rui Zhang ◽  
Lingyun Zheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Liquid Sodium ◽  
Heat Transfer Characteristics ◽  
Backward Facing Step ◽  
Heating Wall ◽  
Transfer Characteristics ◽  
Cfd Models ◽  
Flow And Heat Transfer

The prediction of flow and heat transfer characteristics of liquid sodium with CFD technology is of significant importance for the design and safety analysis of sodium-cooled fast reactor. The accuracies and uncertainties of the CFD models should be evaluated to improve the confidence of the numerical results. In this work, the uncertainties from the turbulent model, boundary conditions, and physical properties for the flow and heat transfer of liquid sodium were evaluated against the experimental data. The results of uncertainty quantization show that the maximum uncertainties of the Nusselt number and friction coefficient occurred in the transition zone from the inlet to the fully developed region in the circular tube, while they occurred near the reattachment point in the backward-facing step. Furthermore, in backward-facing step flow, the maximum uncertainty of temperature migrated from the heating wall to the geometric center of the channel, while the maximum uncertainty of velocity occurred near the vortex zone. The results of sensitivity analysis illustrate that the Nusselt number was negatively correlated with the thermal conductivity and turbulent Prandtl number, while the friction coefficient was positively correlated with the density and Von Karman constant. This work can be a reference to evaluate the accuracy of the standard k-ε model in predicting the flow and heat transfer characteristics of liquid sodium.

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