Cooling Performance of Using a Confined Slot Jet Impinging onto Heated Heat Sinks

2005 ◽  
Vol 128 (1) ◽  
pp. 82-91 ◽  
Author(s):  
Ta-Wei Lin ◽  
Ming-Chang Wu ◽  
Li-Kang Liu ◽  
Chun-Jen Fang ◽  
Ying-Huei Hung
Keyword(s):  
Steady State ◽  
Jet Impingement ◽  
Separation Distance ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Width Ratio ◽  
Cooling Performance ◽  
Nusselt Numbers ◽  
Data Regression ◽  
Good Agreement

A series of experimental investigations on the studies related to transient- and steady-state cooling performance from the horizontally heated heat sinks with a confined slot jet impingement have been conducted. The relevant parameters influencing the transient convective cooling performance include the steady-state Grashof number, ratio of jet separation distance to nozzle width, ratio of heat sink height to nozzle width, and jet Reynolds number. The transient heat transfer behaviors such as the temperature distribution, local and average Nusselt numbers on the heated heat sinks have been systematically explored. Two empirical correlations of steady-state local and average Nusselt numbers are presented. Furthermore, a complete composite correlation of steady-state average Nusselt number for mixed convection due to jet impingement and buoyancy is proposed. This empirical correlation obtained by data regression is in good agreement with the experimental data. The maximum and average regression errors are 7.46% and 2.87%, respectively.

Cooling Performance of Plain-Plate-Fin Heat Sinks With Slot Jet Impingement

2006 ◽  
Author(s):  
M. C. Wu ◽  
Y. C. Lee ◽  
C. H. Peng ◽  
C. J. Fang ◽  
Y. H. Hung
Keyword(s):  
Experimental Data ◽  
Thermal Performance ◽  
Heat Sink ◽  
Jet Impingement ◽  
Separation Distance ◽  
Heat Sinks ◽  
Cooling Performance ◽  
Nusselt Numbers ◽  
New Correlation ◽  
Generalized Correlation

An experimental investigation on the thermal performance of slot jet impinging onto fully-confined and partially-confined heat sinks with plain-plate fins (ppf) is presented. The relevant parameters influencing the convective cooling performance with slot jet impingement include the ratio of heat sink height to jet separation distance (Hs/H), ratio of heat sink height to nozzle width (Hs/Wj) and jet Reynolds number (Rej). The thermal performance of fully-confined ppf heat sinks (Hs/H=1) is experimentally investigated. Besides, an effective theoretical model based on a developing channel flow with an impinging effect is successfully proposed to predict the average Nusselt numbers of fully-confined ppf heat sinks. Furthermore, a new correlation of average Nusselt numbers in terms of Hs/Wj and Rej is proposed for the cases of fully-confined ppf heat sinks. For partially-confined cases, a normalized Nusselt number, [Equation]Nuj/[Equation]Nuj,Hs/H=1, is showed only dependent on Hs/H in the present study. A new correlation of [Equation]Nuj/[Equation]Nuj,Hs/H=1 in terms of Hs/H is proposed. This result manifests that the Nusselt numbers of partially-confined ppf heat sinks can properly be evaluated with the Nusselt numbers of fully-confined heat sinks and the normalized [Equation]Nuj/[Equation]Nuj,Hs/H=1 ratios. Finally, a generalized correlation of average Nusselt numbers in terms of Hs/H, Hs/Wj and Rej, which can be applied to both fully-confined and partially-confined heat sinks, is proposed. The maximum and average deviations between the correlations and the experimental data are 19.7% as well as 4.6%, respectively.

Convective Heat Transfer From a Stationary or Rotating MCM Disk With a Unconfined Round Jet Impingement

2005 ◽  
Author(s):  
Y. M. Kuo ◽  
C. J. Fang ◽  
M. C. Wu ◽  
C. H. Peng ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steady State ◽  
Mixed Convection ◽  
Jet Impingement ◽  
Disk Surface ◽  
Separation Distance ◽  
Heat Flux Distribution ◽  
Disk Rotation ◽  
Nusselt Numbers

A series of experimental investigations with stringent measurement methods on the studies related to fluid flow and transient mixed convection from a horizontally unconfined stationary or rotating ceramic-based MCM disk with unconfined jet impingement have been successfully conducted. The relevant parameters influencing fluid flow and heat transfer performance are (1) mixed convection due to jet impingement and buoyancy: steady-state Grashof number, jet Reynolds number, and ratio of jet separation distance to nozzle diameter; and (2) mixed convection due to jet impingement, disk rotation and buoyancy: steady-state Grashof number, jet Reynolds number (Rej), rotational Reynolds number (Rer), ratio of jet separation distance to nozzle diameter (H/d). The thermal behavior explored includes the transient temperature distribution on the MCM disk surface, transient heat flux distribution of input power, transient convective heat flux distribution of chips, and transient chip and average heat transfer characteristics on the MCM disk surface. Besides, two new correlations of transient stagnation and average Nusselt numbers in terms of Rej, H/d and t are presented for the cases of stationary MCM disk. For the cases of rotating MCM disk, a new empirical correlation to classify two regimes of heat transfer modes such as disk rotation mode and jet impingement mode is presented; and a complete composite correlation of steady-state average Nusselt number for mixed convection due to jet impingement, disk rotation and buoyancy is proposed. As compared with the steady-state results, if the transient chip and average heat transfer behaviors may be considered as a superposition of a series of quasi-steady states, the transient chip and average Nusselt numbers in all the present transient experiments can be properly predicted by the existing steady-state correlations when t > 6 min in the power-on transient period.

Transient Convective Heat Transfer of Air Jet Impinging Onto a Confined Ceramic-Based MCM Disk

2001 ◽  
Author(s):  
W. S. Su ◽  
L. K. Liu ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Jet Impingement ◽  
Disk Surface ◽  
Separation Distance ◽  
Transient Time ◽  
Nusselt Numbers ◽  
Air Jet ◽  
Transient Experiments ◽  
Transfer Behavior

Abstract Transient heat transfer behavior from a horizontally confined ceramic-based MCM disk with jet impingement has been systematically explored. The relevant parameters influencing heat transfer performance are the steady-state Grashof number, jet Reynolds number, and ratio of jet separation distance to nozzle diameter. In addition, an effective time, ton, representing a certain transient time when the mixed convection effect due to jet impingement and buoyancy becomes significant relative to heat conduction, is introduced. Both the transient chip and average Nusselt numbers on the MCM disk surface decrease with time in a very beginning period of 0 ≤ t < ton, whereas it gradually increases or keeps constant with time and finally approaches the steady-state value in the period of ton ≤ t < ts. As compared with the steady-state results, if the transient chip and average heat transfer behaviors may be considered as a superposition of a series of quasi-steady states, the transient chip and average Nusselt numbers in all the present transient experiments can be properly predicted by the existing steady-state correlations when t ≥ 4 min in the power-on transient period.

Transient Convective Heat Transfer of Air Jet Impinging Onto a Confined Ceramic-Based MCM Disk

2004 ◽  
Vol 126 (1) ◽  
pp. 159-172 ◽  
Author(s):  
Li-Kang Liu ◽  
Wen-Shien Su ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Jet Impingement ◽  
Disk Surface ◽  
Separation Distance ◽  
Transient Time ◽  
Nusselt Numbers ◽  
Air Jet ◽  
Transient Experiments ◽  
Transfer Behavior

Transient heat transfer behavior from a horizontally confined ceramic-based MCM disk with jet impingement has been systematically explored. The relevant parameters influencing heat transfer performance are the steady-state Grashof number, jet Reynolds number, and ratio of jet separation distance to nozzle diameter. In addition, an effective time, ton, representing a certain transient time when the mixed convection effect due to jet impingement and buoyancy becomes significant relative to heat conduction, is introduced. Both the transient chip and average Nusselt numbers on the MCM disk surface decrease with time in a very beginning period of 0⩽t<ton, whereas it gradually increases or keeps constant with time and finally approaches the steady-state value in the period of ton⩽t<ts. As compared with the steady-state results, if the transient chip and average heat transfer behaviors may be considered as a superposition of a series of quasi-steady states, the transient chip and average Nusselt numbers in all the present transient experiments can be properly predicted by the existing steady-state correlations when t⩾4min in the power-on transient period.

Convective Heat Transfer From Confined Heated Surfaces With Slot Jet Impingement

2005 ◽  
Author(s):  
L. K. Liu ◽  
C. J. Fang ◽  
M. C. Wu ◽  
C. H. Peng ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Steady State ◽  
Convective Heat ◽  
Local Nusselt Number ◽  
Jet Impingement ◽  
Experimental Investigations ◽  
Surface Center ◽  
Nusselt Numbers ◽  
Extended Surface

A series of experimental investigations with a stringent measurement method on the transient-/steady-state heat transfer behavior for confined smooth surfaces with slot jet impingement have been successfully conducted. From the results, a generalized correlation is proposed to represent the distributions of normalized transient convective heat flux. The highest heat transfer during the transient period occurs at the surface center of confined heated smooth or extended surface. The transient local Nusselt number decreases along the distance from the surface center toward the surface edge. The transient-/steady-state local and average Nusselt numbers are almost independent of Grs, and they are more significantly affected by ReD as compared with H/W. They will increase with increasing ReD. Maximum local and average Nusselt numbers can be found between H/W = 3 and H/W = 5. The effects of Grs and H/W on the dimensionless local Nusselt number distribution are insignificant; and the distribution can be expressed as a generalized bell-shaped profile, which is only dependent of ReD. Finally, a new composite correlation of steady-state average Nusselt number for mixed convection from confined smooth due to slot jet impingement and buoyancy are presented.

Heat Transfer Experiments in a Confined Jet Impingement Configuration Using Transient Techniques

2010 ◽  
Author(s):  
Florian Hoefler ◽  
Nils Dietrich ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Direction ◽  
Jet Impingement ◽  
Thermochromic Liquid Crystal ◽  
Transient Techniques ◽  
Nusselt Numbers ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

A confined jet impingement configuration has been investigated in which the matter of interest is the convective heat transfer from the airflow to the passage walls. The geometry is similar to gas turbine applications. The setup is distinct from usual cooling passages by the fact that no crossflow and no bulk flow direction are present. The flow exhausts through two staggered rows of holes opposing the impingement wall. Hence, a complex 3-D vortex system arises, which entails a complex heat transfer situation. The transient Thermochromic Liquid Crystal (TLC) method was used to measure the heat transfer on the passage walls. Due to the nature of the experiment, the fluid as well as the wall temperature vary with location and time. As a prerequisite of the transient TLC technique, the heat transfer coefficient is assumed to be constant over the transient experiment. Therefore, additional measures were taken to qualify this assumption. The linear relation between heat flux and temperature difference could be verified for all measurement sites. This validates the assumption of a constant heat transfer coefficient which was made for the transient TLC experiments. Nusselt number evaluations from all techniques show a good agreement, considering the respective uncertainty ranges. For all sites the Nusselt numbers range within ±9% of the values gained from the TLC measurement.

Convective Heat Transfer From Heated Extended Surfaces With a Confined Slot Jet Impingement

2004 ◽  
Author(s):  
L. K. Liu ◽  
M. C. Wu ◽  
C. J. Fang ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Separation Distance ◽  
Nusselt Numbers ◽  
Transfer Behavior ◽  
Extended Surfaces

A series of experimental investigations with stringent measurement methods on the studies related to mixed convection from the horizontally confined extended surfaces with a slot jet impingement have been successfully conducted. The relevant parameters influencing mixed convection performance due to jet impingement and buoyancy include the Grashof number, ratio of jet separation distance to nozzle width, ratio of extended surfaces height to nozzle width and jet Reynolds number. The range of these parameters studied are Grs = 3.77 × 105 – 1.84 × 106, H/W = 1–10, Hs/W = 0.74–3.40 and Re = 63–1383. In the study, the heat transfer behavior on the extended surfaces with confined slot jet impingement such as the temperature distribution, local and average Nusselt numbers on the extended surfaces has been systematically explored. The results manifest that the effect of steady-state Grashof number on heat transfer behavior such as stagnation, local and average Nusselt number is not significant; while the heat transfer performance increases with decreasing jet separation distance or with increasing extended surface height and jet Reynolds number. Besides, two new correlations of local and average Nusselt numbers in terms of H/W, Hs/W and Re are proposed for the cases of extended surfaces. A satisfactory agreement is achieved between the results predicted by these correlations and the experimental data. Finally, a complete composite correlation of steady-state average Nusselt number for mixed convection due to jet impingement and buoyancy is proposed. The comparison of the predictions evaluated by this correlation with all the present experimental data is made. The maximum and average deviations of the predictions from the experimental data are 7.46% and 2.87%, respectively.

Thermal Optimal Design for Multichip Module Disks With an Unconfined Round-Jet Impingement

2005 ◽  
Author(s):  
C. J. Fang ◽  
M. C. Wu ◽  
C. H. Peng ◽  
Y. C. Lee ◽  
Y. H. Hung
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Steady State ◽  
Thermal Performance ◽  
Jet Impingement ◽  
Separation Distance ◽  
Grashof Number ◽  
Round Jet ◽  
Space Limitation

An effective method for performing the thermal optimization of stationary and rotating MCM disks with an unconfined round-jet impingement under space limitation constraint has been successfully developed. The design variables of stationary and rotating MCM disks with an unconfined round-jet impingement include: the ratio of jet separation distance to nozzle diameter (H/d), steady-state Grashof number (Grs), jet Reynolds number (Rej), rotational Reynolds number (Rer). The total experimental cases for stationary and rotating MCM disks are statistically designed by the Central Composite Design (CCD) method. In addition, a sensitivity analysis, the so-called ANOVA, for the design factors has been performed. In the stationary MCM disk with an unconfined round-jet impingement, the contribution percentage of jet Reynolds number on the thermal performance is 95.86%. The effect of jet Reynolds numbers on chip temperature distribution is more significant than that of the H/d ratio and steady-state Grashof number. In rotating MCM disk with an unconfined round-jet impingement, the effect of jet Reynolds number, which has the contribution percentage of 91.81%, dominates the thermal performance. Furthermore, the comparisons between the predictions by using the quadratic Response Surface Methodology (RSM) and the experimental data are made. The maximum deviations for transient stagnation Nusselt number and transient average Nusselt number for the cases of stationary MCM disk are 10.05% and 11.82%, respectively; and 9.41% and 12.44% for the cases of rotating MCM disk, respectively. Finally, with the Sequential Quadratic Programming (SQP) technique, a series of thermal optimal designs under space limitation constraint H/d≤12 has been efficiently performed. Comparisons between the numerical optimization results and the experimental data are made with a satisfactory agreement.

Heat Transfer Characteristics for a Confined Rotating MCM Disk With Round Jet Array Impingement

2007 ◽  
Author(s):  
C. Y. Lee ◽  
C. J. Fang ◽  
C. H. Peng ◽  
T. W. Lin ◽  
Y. H. Hung
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steady State ◽  
Jet Impingement ◽  
Separation Distance ◽  
Heat Transfer Characteristics ◽  
Round Jet ◽  
Transfer Characteristics ◽  
Disk Rotation ◽  
Jet Array

An effective method of design of experiments combined with Central Composite Design for exploring the heat transfer characteristics for a confined rotating Multi-Chip Module (MCM) disk with round jet array impingement has been successfully developed. The relevant parameters influencing heat transfer performance include the steady-state Grashof number (Grs), ratio of jet separation distance to nozzle diameter (H/d), jet Reynolds number (Rej) and rotational Reynolds number (Rer). Their effects on heat transfer characteristics have been systematically explored. An axisymmetrical temperature distribution is ensured for various Grs, Rej, Rer and H/d ratios. As compared with the mutual effects of jet array impingement and disk rotation cause a more non-uniform distribution of chip temperatures. For heat transfer behavior, a new correlation of stagnation Nusselt number for jet array impingement at r/R = 0 in terms of Rej and H/d is presented. As compared with the experimental steady-state data of single round jet impingement, the average heat transfer enhancement at stagnation point r/R = 0 of jet array impingement is 607%. For the rotating MCM disk cases, the highest chip heat transfer occurs at the MCM disk rim, and decreases sharply along the distance from the surface edge toward the surface center.

scholarly journals Vibration and cooling performances of piezoelectric cooling fan: numerical and experimental investigations

2020 ◽  
Vol 306 ◽  
pp. 04002
Author(s):  
Thomas Jin-Chee Liu ◽  
Yu-Shen Chen ◽  
Hsi-Yang Ho ◽  
Jyun-Ting Liu
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Experimental Methods ◽  
Experimental Investigations ◽  
Experimental Measurements ◽  
Cooling Performance ◽  
Optimal Geometry ◽  
Cooling Fan ◽  
Fan Blade ◽  
Good Agreement

In this paper, the vibration and cooling performances of the piezoelectric cooling fan are studied. The finite element and experimental methods are adopted for the analyses. The natural frequency, mode shape, flapping amplitude, and cooling performance are discussed for the primary design. The numerical results have good agreement with the experimental measurements. For the cooling purpose, the piezoelectric cooling fan has to work under the natural frequency. The aspect ratio 2:3 is the optimal geometry of the fan blade.

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