scholarly journals A Review of Thermo-Hydraulic Performance of Metal Foam and its Application as Heat Sinks for Electronics Cooling

2020 ◽  
Author(s):  
Yongtong Li ◽  
Liang Gong ◽  
Minghai Xu ◽  
Yogendra Joshi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Metal Foam ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Metal Foams ◽  
Hydraulic Performance ◽  
Heat Sinks ◽  
Research Progress ◽  
High Porosity

Abstract High porosity metal foams offer large surface area per unit volume and have been considered as effective candidates for convection heat transfer enhancement, with applications as heat sinks in electronics cooling. In this paper, the research progress in thermo-hydraulic performance characterization of metal foams and their application as heat sinks for electronics cooling are reviewed. We focus on natural convection, forced convection, flow boiling, and solid/liquid phase change using phase change materials (PCMs). Under these heat transfer conditions, the effects of various parameters influencing the performance of metal foam heat sink are discussed. It is concluded that metal foams demonstrate promising capability for heat transfer augmentation, but some key issues still need to be investigated regarding the fundamental mechanisms of heat transfer to enable the development of more efficient and compact heat sinks.

Geometric Mean of Fin Efficiency and Effectiveness: A Parameter to Determine Optimum Length of Open-Cell Metal Foam Used as Extended Heat Transfer Surface

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Tisha Dixit ◽  
Indranil Ghosh
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Geometric Mean ◽  
Fluid Velocity ◽  
High Surface ◽  
Metal Foams ◽  
Heat Sinks ◽  
High Porosity ◽  
Open Cell ◽  
Fin Efficiency

High porosity open-cell metal foams have captured the interest of thermal industry due to their high surface area density, low weight, and ability to create tortuous mixing of fluid. In this work, application of metal foams as heat sinks has been explored. The foam has been represented as a simple cubic structure and heat transfer from a heated base has been treated analogous to that of solid fins. Based on this model, three performance parameters namely, foam efficiency, overall foam efficiency, and foam effectiveness have been evaluated for metal foam heat sinks. Parametric studies with varying foam length, porosity, pore density, material, and fluid velocity have been conducted. It has been observed that geometric mean of foam efficiency and foam effectiveness can be a useful parameter to exactly determine the optimum foam length. Additionally, the variation in temperature profile of different foams heated from one end has been determined experimentally by cooling these with atmospheric air. The experimental results have been presented for open-cell metal foams (10 and 30 PPI) made of copper/aluminium/Fe–Ni–Cr alloy with porosity in the range of 0.908–0.964.

Jet Impingement Heat Transfer Enhancement by Packing High-Porosity Thin Metal Foams Between Jet Exit Plane and Target Surface

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Metal Foam ◽  
Jet Impingement ◽  
Target Surface ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pumping Power ◽  
Transfer Enhancement

High-porosity metal foams are known for providing high heat transfer rates, as they provide a significant increase in wetted surface area as well as highly tortuous flow paths resulting in enhanced mixing. Further, jet impingement offers high convective cooling, particularly at the jet footprint areas on the target surface due to flow stagnation. In this study, high-porosity thin metal foams were subjected to array jet impingement, for a special crossflow scheme. High porosity (92.65%), high pore density (40 pores per inch (ppi)), and thin foams (3 mm) have been used. In order to reduce the pumping power requirements imposed by full metal foam design, two striped metal foam configurations were also investigated. For that, the jets were arranged in 3 × 6 array (x/dj = 3.42, y/dj = 2), such that the crossflow is dominantly sideways. Steady-state heat transfer experiments have been conducted for varying jet-to-target plate distance z/dj = 0.75, 2, and 4 for Reynolds numbers ranging from 3000 to 12,000. The baseline case was jet impingement onto a smooth target surface. Enhancement in heat transfer due to impingement onto thin metal foams has been evaluated against the pumping power penalty. For the case of z/dj = 0.75 with the base surface fully covered with metal foam, an average heat transfer enhancement of 2.42 times was observed for a concomitant pressure drop penalty of 1.67 times over the flow range tested.

Thermal and Mechanical Modeling of Metal Foams for Thermal Interface Application

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Ninad Trifale ◽  
Eric Nauman ◽  
Kazuaki Yazawa
Keyword(s):  
Thermal Resistance ◽  
Metal Foam ◽  
Electronics Cooling ◽  
Cost Effective ◽  
Metal Foams ◽  
High Porosity ◽  
Pore Density ◽  
Thermal Interface ◽  
Interface Thermal Resistance ◽  
Thermally Conductive

We present a study on the apparent thermal resistance of metal foams as a thermal interface in electronics cooling applications. Metal foams are considered beneficial for several applications due to its significantly large surface area for a given volume. Porous heat sinks made of aluminum foam have been well studied in the past. It is not only cost effective due to the unique production process but also appealing for the theoretical modeling study to determine the performance. Instead of allowing the refrigerant flow through the open cell porous medium, we instead consider the foam as a thermal conductive network for thermal interfaces. The porous structure of metal foams is moderately compliant providing a good contact and a lower thermal resistance. We consider foam filled with stagnant air. The major heat transport is through the metal struts connecting the two interfaces with high thermally conductive paths. We study the effect of both porosity and pore density on the observed thermal resistance. Lower porosity and lower pore density yield smaller bulk thermal resistance but also make the metal foam stiffer. To understand this tradeoff and find the optimum, we developed analytic models to predict intrinsic thermal resistance as well as the contact thermal resistance based on microdeformation at the contact surfaces. The variants of these geometries are also analyzed to achieve an optimum design corresponding to maximum compliance. Experiments are carried out in accordance with ASTM D5470 standard. A thermal resistance between the range 17 and 5 K cm2/W is observed for a 0.125 in. thick foam sample tested over a pressure range of 1–3 MPa. The results verify the calculation based on the model consisting the intrinsic thermal conductivity and the correlation of constriction resistance to the actual area of contact. The area of contact is evaluated analytically as a function of pore size (5–40 PPI), porosity (0.88–0.95), orientation of struts, and the cut plane location of idealized tetrakaidecahedron (TKDH) structure. The model is developed based on assumptions of elastic deformations and TKDH structures which are applicable in the high porosity range of 0.85–0.95. An optimum value of porosity for minimizing the overall interface thermal resistance was determined with the model and experimentally validated.

Melting of Phase Change Materials With Volume Change in Metal Foams

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Zhen Yang ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Phase Change ◽  
Volume Change ◽  
Phase Change Materials ◽  
Metal Foam ◽  
Melting Process ◽  
Metal Foams ◽  
Volume Shrinkage ◽  
Two Temperature

Melting of phase change materials (PCMs) embedded in metal foams is investigated. The two-temperature model developed accounts for volume change in the PCM upon melting. Volume-averaged mass and momentum equations are solved, with the Brinkman–Forchheimer extension to Darcy’s law employed to model the porous-medium resistance. Local thermal equilibrium does not hold due to the large difference in thermal diffusivity between the metal foam and the PCM. Therefore, a two-temperature approach is adopted, with the heat transfer between the metal foam and the PCM being coupled by means of an interstitial Nusselt number. The enthalpy method is applied to account for phase change. The governing equations are solved using a finite-volume approach. Effects of volume shrinkage/expansion are considered for different interstitial heat transfer rates between the foam and PCM. The detailed behavior of the melting region as a function of buoyancy-driven convection and interstitial Nusselt number is analyzed. For strong interstitial heat transfer, the melting region is significantly reduced in extent and the melting process is greatly enhanced as is heat transfer from the wall; the converse applies for weak interstitial heat transfer. The melting process at a low interstitial Nusselt number is significantly influenced by melt convection, while the behavior is dominated by conduction at high interstitial Nusselt numbers. Volume shrinkage/expansion due to phase change induces an added flow, which affects the PCM melting rate.

Effect of Metal Foam Thickness and Pore Density on Array Jet Impingement Heat Transfer

2019 ◽  
Author(s):  
Prashant Singh ◽  
Mingyang Zhang ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Heated Surface ◽  
Jet Impingement ◽  
Hydraulic Performance ◽  
Convective Transport ◽  
High Porosity ◽  
Pore Density ◽  
Foam Thickness ◽  
Jet Array

Abstract High porosity metal foam is a popular option for high performance heat exchangers as it offers significantly larger area per unit volume for heat dissipation as compared to other cooling techniques by convection. Further, metal foams provide highly tortuous flow paths resulting in thermal dispersion assisted by enhanced mixing. This paper reports an experimental study on jet array impingement onto high-porosity (ε∼0.95) thin aluminum foams. Our goal was to study the effect of foam thickness on convective transport and determine the optimum combination of foam thickness and pore density for maximum gain in thermal-hydraulic performance. To this end, three different pore-density foams (5, 10 and 20 pores per inch, ppi) were tested with three different jet array (5 × 5) impingement configurations (x/dj = 2,3 and 5), where “x” is the distance between any two adjacent jets and “dj” is the jet diameter. For the three pore densities selected, six values of foam thickness — 6.35 mm, 12.7 mm and 19.05 mm for the 20 ppi foam, 12.7 mm and 19.05 mm for the 10 ppi foam, and 12.7 mm for the 5 ppi foam — were deployed. The minimum thickness for each of the ppi value was dictated by the vendor’s manufacturing constraint. The thermal performance of these foams was compared against the orthogonal jet impingement onto a smooth heated surface, for which the distance between the jet exit plane and the heated surface was maintained at the foam thickness level. The data indicates that for a given pore density, thin foams have higher heat transfer rates compared to those for thicker foams, especially with jet configurations with larger open area ratios. The gain is due to the increased jet penetration and foam volume usage in thin foams compared to those for thick foams. Of the different pore density and foam thickness combinations, a 12.70 mm/20 ppi combination was found to have the highest thermal hydraulic performance.

Buoyancy-Induced Convection in Metal Foam and Finned Metal Foam Heat Sinks©

2000 ◽  
Author(s):  
A. Bhattacharya ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Metal Foam ◽  
Metal Foams ◽  
Experimental Results ◽  
Heat Sinks ◽  
Normal Metal ◽  
Optimum Number

Abstract In this paper, we present our recent experimental results on buoyancy induced convection in metal foams of different pore densities (corresponding to 5, 10, 20 and 40 pores per inch) and porosities (0.89–0.96). The results show that compared to a hot surface facing up, the heat transfer coefficients in these heat sinks are 5 to 6 times higher. However, when compared to commercially available heat sinks of similar dimensions, the enhancement is found to be marginal. The experimental results also show that for a given pore size, the heat transfer rate increases with porosity suggesting the dominant role played by conduction in enhancing heat transfer. On the other hand, if the porosity is held constant, the heat transfer rate is found to be lower at higher pore densities. This can be attributed to the higher permeability with the larger pores, which allows higher entrainment of air through the porous medium. An empirical correlation, developed for the estimation of Nusselt number in terms of Rayleigh and Darcy numbers, is found to be in good agreement with the experimental data with a maximum error of 10%. We also report our results on novel finned metal foam heat sinks© in natural convection. Experiments were conducted on aluminum foams of 90% porosity with 5 and 20 PPI (pores per inch) with one, two, and four aluminum fins inserted in the foam. All these heat sinks were fabricated in-house. The results show that the finned metal foam heat sinks© are superior in thermal performance compared to the normal metal foam and conventional finned heat sinks. The heat transfer increases with increase in the number of fins. However, the relative enhancement is found to decrease with each additional fin. The indication is that there exists an optimum number of fins beyond which the enhancement in heat transfer due to increased surface area is offset by the retarding effect of overlapping thermal boundary layers. Similar to normal metal foams, the 5 PPI samples are found to give higher values of the heat transfer coefficient compared to the 20 PPI samples due to higher permeability of the porous medium. Future work is planned to arrive at the optimal heat sink configuration for even larger enhancement in heat transfer.

Heat Transfer Enhancement Through Array Jet Impingement on Strategically Placed High Porosity High Pore-Density Thin Copper Foams

2020 ◽  
Author(s):  
Varun Prasanna Rajamuthu ◽  
Sanskar Panse ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Hydraulic Performance ◽  
High Porosity ◽  
Heat Transfer Area ◽  
Pore Density ◽  
Pumping Power ◽  
Foam Volume ◽  
Copper Foam ◽  
Jet Array

Abstract High porosity, high pore-density (pores per inch: PPI) metal foams are a popular choice in high heat flux cooling applications as they offer large heat transfer area over a given volume, however, accompanied by a concomitant increase in pumping power requirements. Present experimental study aims towards developing a novel metal-foam based cooling configuration featuring thin copper foams (3 mm) subjected to orthogonal air jet array impingement. The foam configurations allowed strategic and selective placement of high pore-density (90 PPI) and high porosity (~ 96%) copper foam on the heated surface with respect to the jet array in the form of foam stripes aiming to enhance heat transfer and reduce pressure drop penalty. The thermal-hydraulic performance was evaluated over range of Reynolds numbers, jet-to-jet (x/dj ,y/dj) and jet-to-target (z/dj) spacings and compared with a baseline smooth surface. The effect of pore-density was further analyzed by studying 40 PPI copper foam and compared with corresponding 90 PPI foam arrangement. The thermal-hydraulic performance was found to be governed by combinational interaction of three major factors: heat transfer area, ease of jet penetration and foam volume usage. Strategic placement of metal foam stripes allowed better utilization of the foam heat transfer area and available foam volume by aiding penetration of coolant fluid through available foam thickness. Thus, performing better than the case where entire heat transfer area was covered with foam. For a fixed pumping power of 10 W, the optimal metal foam-jet configuration showed ~50% higher heat transfer with negligible increase in pumping power requirements.

Direct Simulation of Interstitial Heat Transfer Coefficient Between Paraffin and High Porosity Open-Cell Metal Foam

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Change Process ◽  
Energy Equation ◽  
Metal Foam ◽  
Equation Model ◽  
High Porosity ◽  
Direct Simulation ◽  
Open Cell ◽  
Transfer Region

The interstitial heat transfer coefficient (IHTC) is a key parameter in the two-energy equation model usually employed to investigate the thermal performance of high porosity open-cell metal foam/paraffin composite phase change material. Due to the existence of weak convection of liquid paraffin through metal foam during phase change process, the IHTC should be carefully determined for a low Reynolds number range (Re = 0–1), which however has been rarely addressed in the literature. In this paper, a direct simulation at foam pore scale is carried out to determine the IHTC between paraffin and metal foam at Re = 0–1. For this purpose, the cell structures reflecting realistic metal foams are first constructed based on the three-dimensional (3D) Weaire–Phelan foam cell to serve as the representative elementary volume (REV) of metal foam for direct simulation. Then, by solving the Navier–Stokes equations and energy equation for the REV, the influences of Reynolds number (Re), Prandtl number (Pr), foam porosity (ε), and pore density (PPI) on the dimensionless IHTC, i.e., the Nusselt number Nuv, are investigated. According to the numerical results, a correlation of Nuv at Re = 0–1 is proposed for metal foam/paraffin composite material, which covers both diffusion-dominated interstitial heat transfer region (Re ≤ 0.1) and convection-dominated interstitial heat transfer region (0.1 < Re ≤ 1). Finally, the applicability of this correlation in the two-energy equation model for solid–liquid phase change of paraffin in metal foam is validated by comparing the model predicted melting front with that of experimental observations made in this study. It is found that the IHTC correlation proposed in this study can be used in the two-energy equation model for well predicting the phase change process of paraffin in metal foam.

Metal-Foam-Enhanced PCM Storage System: The Cylindrical Shell Geometry

2011 ◽  
Author(s):  
Nihad Dukhan
Keyword(s):  
Heat Transfer ◽  
Cylindrical Shell ◽  
Phase Change ◽  
Change Process ◽  
Metal Foam ◽  
Storage System ◽  
Open Loop ◽  
High Porosity ◽  
Phase Change Process ◽  
Thermal Conductivities

Phase-change systems remain to be widely used for storage of thermal energy such as the energy harnessed by solar collectors. The major disadvantage of phase change materials (PCMs) is their low thermal conductivities, which drastically slows the phase change process and causes wide temperature variations within PCMs, while requiring heat transfer area. Metal foams are one class of porous media that possess thermal conductivities that are an order of magnitude higher than PCMs. When embedded in PCMs, the random internal structure and high porosity of metal foam enhance and accelerate the phase change process without significantly reducing PCMs’ heat storage capacity. Unlike traditional PCM systems, the distribution of the foam ligaments in PCMs makes the melting and solidification processes uniform and less dependent on location inside PCMs. This also leads to shorter charging and discharging times. The design, fabrication and characterization of a small PCM-metal-foam thermal storage system are described in this paper. The core of the system is a cylindrical shell composed of 90%-porous open-cell aluminum foam filled with Paraffin-based PCM. The foam occupies only 10% of the total volume. The shell walls were fabricated from copper. The system was tested in an open loop wind tunnel. Results for the convection heat transfer coefficient and the effect of volumetric flow rate on the system’s performance were obtained. The heat transfer rate from the system was computed and discussed.

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