Effects of jet-to-disk separation distance on the characteristics of mixed convective vortex flow in an impinging air jet confined in a cylindrical chamber

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.

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Heat-Transfer Optimization for Multichip Module Disks With an Unconfined Round Air Jet Impingement

Journal of Electronic Packaging ◽

10.1115/1.2804089 ◽

2007 ◽

Vol 129 (4) ◽

pp. 411-420

Author(s):

Y. C. Lee ◽

C. J. Fang ◽

M. C. Wu ◽

C. H. Peng ◽

Y. H. Hung

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Design Method ◽

Jet Impingement ◽

Separation Distance ◽

Multichip Module ◽

Programming Technique ◽

Grashof Number ◽

Round Jet ◽

Air Jet

An effective method for performing the thermal optimization of stationary and rotating multichip module (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, Grashof number, jet Reynolds number, and rotational Reynolds number. The total experimental cases for stationary and rotating MCM disks are statistically designed by the central composite design method. In addition, a sensitivity analysis, the so-called analysis of variance, for the design factors has been performed. Among the influencing parameters, the jet Reynolds number dominates the thermal performance, while the Grashof number is found to have the least effect on heat-transfer performance for both stationary and rotating cases. Furthermore, the comparisons between the predictions by using the quadratic response surface methodology and the experimental data for both stationary and rotating cases are made with a satisfactory agreement. Finally, with the sequential quadratic programming technique, a series of thermal optimizations under multiconstraints—such as space, jet Reynolds number, rotational Reynolds number, nozzle exit velocity, disk rotational speed, and various power consumptions—has been systematically explored and discussed.

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

Journal of Electronic Packaging ◽

10.1115/1.1649239 ◽

2004 ◽

Vol 126 (1) ◽

pp. 159-172 ◽

Cited By ~ 10

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.

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Evaporation at a Liquid Surface Due to Jet Impingement

Journal of Heat Transfer ◽

10.1115/1.3246939 ◽

1986 ◽

Vol 108 (2) ◽

pp. 411-417 ◽

Cited By ~ 3

Author(s):

E. M. Sparrow ◽

S. W. Celere ◽

L. F. A. Azevedo

Keyword(s):

Mass Transfer ◽

Transfer Coefficient ◽

Water Surface ◽

Liquid Surface ◽

Jet Impingement ◽

Separation Distance ◽

Operating Conditions ◽

Transfer Coefficients ◽

Mass Transfer Coefficients ◽

Air Jet

Experiments were performed to determine mass transfer coefficients for evaporation from a water surface on which an air jet impinged. During the course of the experiments, parametric variations were made of the jet velocity and diameter, the separation distance between the jet origin and the water surface, the diameter of the water surface, and the degree of insulation of the water containment pan. It was found that for all of the investigated operating conditions, the dimensionless mass transfer coefficient varied with the 0.8 power of the jet Reynolds number. Furthermore, the transfer coefficient decreased linearly as the separation distance between the jet origin and the water surface increased, with the most significant decreases occurring at relatively small values of the surface-to-jet diameter ratio. At larger diameter ratios, the transfer coefficient was relatively insensitive to the separation. In general, the larger the diameter of the water surface, the lower the transfer coefficient. Comparisons with the literature showed that the dimensionless mass transfer coefficients for impingement on a liquid surface are lower than those for impingement on a solid surface.

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QUANTITATIVE STUDY OF THE HILSCH HEAT SEPARATOR

Canadian Journal of Research ◽

10.1139/cjr47f-037 ◽

1947 ◽

Vol 25f (5) ◽

pp. 299-302 ◽

Cited By ~ 7

Author(s):

A. F. Johnson

Keyword(s):

Quantitative Study ◽

High Velocity ◽

Temperature Drop ◽

Simple Device ◽

Maximum Efficiency ◽

Adiabatic Expansion ◽

Total Flow ◽

Cylindrical Chamber ◽

Air Jet

The 'heat separator' is a very simple device for attaining a temperature drop of the order of 30 centigrade degrees by means of a stream of air. An air jet enters a long cylindrical chamber near one end, and is directed so as to maintain a high velocity vortex. Air drawn off from the centre of the vortex is cooled, while the remainder, flowing down the length of the chamber, is warmed. The present paper describes results of a quantitative study of the performance of the device. Although the maximum efficiency is only about 15%, as compared with an ideal adiabatic expansion of the total flow, it provides a practical means of cooling for many purposes.

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