Heat Transfer and Fluid Flow in Metal Foam Subjected to Oscillating Flow

2005 ◽  
Author(s):  
K. C. Leong ◽  
L. W. Jin
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
High Speed ◽  
Metal Foam ◽  
Substrate Surface ◽  
Volume Ratio ◽  
Porous Channel ◽  
Oscillating Flow ◽  
Open Cell ◽  
Flow Through

The need for higher performance and an increased level of functional integration as well as die size optimization on the microprocessor leads to preferential clustering of higher power units on the processor. Conventional natural or forced convection cooling methods are not capable of removing such a high heat flux for maintaining a proper operational temperature. It is imperative to look for new methods of cooling the modern high-speed electronic components. The porous medium has emerged as an effective method of heat transfer enhancement due to its large surface area to volume ratio and intense mixing of fluid flow. Many researchers have studied heat transfer and fluid flow in a channel filled with metal particles or woven-screens. However, uni-directional flow through the porous channel yields a relatively high temperature difference along the flow direction on the substrate surface. For modern high-speed microprocessors, the reliability of transistors and operating speed are not only influenced by the average temperature but also by temperature uniformity on the substrate surface. Therefore, maintaining the uniformity of on-die temperature distribution below certain limits is imperative in thermal design. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution, due to the presence of two thermal entrance regions for oscillating flow. In the present investigation, a novel porous material of open-cell metal foam was employed to study heat transfer and fluid flow of oscillating flow through a porous channel. The metal foam with fully inter-connected structure, large surface area to volume ratio and high permeability lends itself to applications in electronics cooling. This paper describes an experimental study on heat transfer and pressure drop behavior of oscillating flow through a channel filled with open-cell aluminum foam. Both cycle-averaged and length-averaged local Nusselt numbers were calculated to evaluate heat transfer rate of oscillating flow in metal foam channel. The effects of the dimensionless flow amplitude and frequency of oscillating flow on heat transfer were analyzed. A correlation equation of maximum friction factor of oscillating flow in metal foam was obtained and compared with the results for wire-screens obtained by other investigators under the oscillating flow condition. The results revealed that heat transfer performance can be enhanced substantially by oscillating flow through metal foam with moderate pressure drop.

Heat Transfer Characteristics of Oscillating Flow Through Highly Porous Medium

2006 ◽  
Author(s):  
L. W. Jin ◽  
K. C. Leong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Metal Foam ◽  
Metal Foams ◽  
Porous Channel ◽  
Oscillating Flow ◽  
Transient Temperature ◽  
Heat Transfer Characteristics ◽  
Flow Through ◽  
Highly Porous

Heat transfer in porous media has been investigated extensively with the motivation of enhancing heat removal in electronics cooling applications. Many investigations have been conducted on heat transfer in a channel filled with porous media. However, steady flow through a porous channel still yield a higher temperature difference along the flow direction. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution due to the two thermal entrance regions of oscillating flow. As compared to a porous channel packed with metal particles, spheres or woven-screens, the highly porous open-cell metal foam possesses a different configuration. The polyhedral pore and reticulated ligament structures provide the extremely large fluid-to-solid contact surface area and tortuous coolant flow path inside the metal foam, which could increase dramatically the overall heat transfer rate. A survey of the literature shows that heat transfer in open-cell metal foam were mostly investigated under steady flow condition. Published literature on heat transfer in metal foams subjected to oscillating flow is scarce. This paper presents both experimental and numerical investigations on the heat transfer characteristics for oscillating flow through highly porous medium. Experiments were carried out to study the effect of the oscillatory frequency on the heat transfer in metal foams with various pore densities. The results show that the local Nusselt number increases with the kinetic Reynolds number. Higher total heat transfer rates for oscillating flow can be obtained by using high pore density metal foam. The numerical simulation is focused on the study of the variations of the transient temperature and Nusselt number at different locations in the porous channel during a complete cycle. The numerical results show that the profile of the transient temperature decreases with the increase of the distance along the vertical direction and the variation of the instantaneous Nusselt number at entrance region is more significant than that at the location close to the center of the porous channel. It is also found that the two-dimensional temperature distributions in the numerical domain are symmetric about the center of the channel at the cycle-steady state. The comparison shows that the results obtained by the simulation are in reasonably good agreement with the experimental data.

scholarly journals Microtomography-based numerical simulations of heat transfer and fluid flow through β -SiC open-cell foams for catalysis

2016 ◽  
Vol 278 ◽  
pp. 350-360 ◽  
Author(s):  
Xiaolei Fan ◽  
Xiaoxia Ou ◽  
Fei Xing ◽  
Glen A. Turley ◽  
Petr Denissenko ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Simulations ◽  
Open Cell ◽  
Flow Through ◽  
Open Cell Foams

Effects of Displacement and Frequency of Oscillating Flow on Heat Transfer in a Porous Channel

2004 ◽  
Author(s):  
L. W. Jin ◽  
K. C. Leong
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Correlation Equation ◽  
Porous Channel ◽  
Oscillating Flow ◽  
Electronic Components ◽  
Flow Displacement ◽  
Dimensionless Amplitude ◽  
Flow Through ◽  
Plate Channel

The development in modern electronics has resulted in rapid increases in power densities for electronic packages. Traditional cooling methods are not capable of removing such high heat fluxes. It is imperative to find new methods to cool high-speed electronic components. One of these methods is to implement a channel filled with a high conductivity porous medium. Many investigations have been conducted on the heat transfer of a channel filled with porous media. However, steady flow through a porous channel still yield a higher temperature difference along the flow direction. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution due to the two thermal entrance regions of oscillating flow. Some researchers have investigated forced convective heat transfer in porous channels in oscillating flow with different kinds of porous media. Their results showed that the operating temperatures of electronic components can be reduced significantly when an oscillatory flow device is employed. However, research into the two critical factors of displacement and frequency for oscillating flow in a porous channel is very sparse. This paper presents the experimental results of an investigation into the effects of varying flow displacement and frequency on heat transfer enhancement in a porous channel subject to oscillating flow. A comparison was made between the heat transfer performance of oscillating flow through a plate channel without a porous medium and a channel filled with sintered metal foam. The maximum displacements of oscillating flow were varied from 52 to 68 mm and frequencies of oscillation ranged from 1 to 10 Hz. The characteristics of pressure drop, the effects of the dimensionless amplitude of displacement and dimensionless frequency of oscillating flow on heat transfer in porous channel were analyzed. The results revealed that heat transfer in oscillating flow is significantly enhanced by employing porous media in a plate channel. The cycle-averaged local Nusselt number increases with both kinetic Reynolds number Reω and the dimensionless amplitude of flow displacement A0. Based on the experimental data, a correlation equation of the length-averaged Nusselt number with the dimensionless parameters of Reω and A0 is obtained for a porous channel with L/Dh = 3. This correlation equation will be useful to determine heat transfer rates in oscillating flow through a porous channel for applications in electronics cooling.

An Experimental Study of Heat Transfer of a Porous Channel Subjected to Oscillating Flow

2000 ◽  
Vol 123 (1) ◽  
pp. 162-170 ◽  
Author(s):  
H. L. Fu ◽  
K. C. Leong ◽  
X. Y. Huang ◽  
C. Y. Liu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Surface Temperature ◽  
Steady Flow ◽  
High Speed ◽  
Flow Direction ◽  
Porous Channel ◽  
Oscillating Flow ◽  
Oscillating Flows ◽  
Nusselt Numbers

Experiments have been conducted to study the heat transfer of a porous channel subjected to oscillating flow. The surface temperature distributions for both steady and oscillating flows were measured. The local and length-averaged Nusselt numbers were analyzed. The experimental results revealed that the surface temperature distribution for oscillating flow is more uniform than that for steady flow. Due to the reversing flow direction, there are two thermal entrance regions for oscillating flow. The length-averaged Nusselt number for oscillating flow is higher than that for steady flow. The length-averaged Nusselt number for both steady and oscillating flows increase linearly with a dimensionless grouping parameter k*/kfDe/L1/2Pe*1/2. The porous channel heat sink subjected to oscillating flow can be considered as an effective method for cooling high-speed electronic devices.

scholarly journals Review and a Theoretical Approach on Pressure Drop Correlations of Flow through Open-Cell Metal Foam

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3153
Author(s):  
Huizhu Yang ◽  
Yongyao Li ◽  
Binjian Ma ◽  
Yonggang Zhu
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Metal Foams ◽  
High Porosity ◽  
Open Cell ◽  
Wide Range ◽  
Flow Through

Due to their high porosity, high stiffness, light weight, large surface area-to-volume ratio, and excellent thermal properties, open-cell metal foams have been applied in a wide range of sectors and industries, including the energy, transportation, aviation, biomedical, and defense industries. Understanding the flow characteristics and pressure drop of the fluid flow in open-cell metal foams is critical for applying such materials in these scenarios. However, the state-of-the-art pressure drop correlations for open-cell foams show large deviations from experimental data. In this paper, the fundamental governing equations of fluid flow through open-cell metal foams and the determination of different foam geometry structures are first presented. A variety of published models for predicting the pressure drop through open-cell metal foams are then summarized and validated against experimental data. Finally, two empirical correlations of permeability are developed and recommended based on the model of Calmidi. Moreover, Calmidi’s model is proposed to calculate the Forchheimer coefficient. These three equations together allow calculating the pressure drop through open-cell metal foam as a function of porosity and pore diameter (or strut diameter) in a wide range of porosities ε = 85.7–97.8% and pore densities of 10–100 PPI. The findings of this study greatly advance our understanding of the flow characteristics through open-cell metal foam and provide important guidance for the design of open-cell metal foam materials for different engineering applications.

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