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.

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.

The Effect of Metal Foam Thickness on Jet Array Impingement Heat Transfer in High-Porosity Aluminum Foams

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Prashant Singh ◽  
Karthik Nithyanandam ◽  
Mingyang Zhang ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Heated Surface ◽  
Jet Impingement ◽  
High Porosity ◽  
Pore Density ◽  
Aluminum Foams ◽  
Power Requirement ◽  
Foam Thickness ◽  
Jet Array

Abstract High-porosity metal foam (MF) is a popular option for high-performance heat exchangers as it offers significantly higher heat transfer participation area per unit volume compared to other convection enhancement cooling methods. Further, metal foams provide highly tortuous flow paths resulting in thermal dispersion assisted by enhanced mixing. This paper presents experimental and numerical studies and the detailed underlying physics of jet array impingement onto high-porosity (ε∼0.95) thin aluminum foams. The jet and foam configurations were designed for the maximum utilization of the foam area for heat transfer and reduced penalty on the pumping power requirement. Three different pore density foams were tested with three different array-jet impingement configurations. The minimum possible thickness for each pore density was tested, viz., 5 pores-per-inch (PPI): 19 mm, 10 PPI: 12.7 mm, and 20 PPI: 6.35 mm. The baseline case for these foam-based jet impingement configurations was the corresponding configuration of orthogonal jet impingement onto a smooth heated surface, where the distance between the jet-issuing plane and the heated surface was maintained at the foam thickness level. In general, thinner foams facilitated greater jet penetration and increased foam volume usage, resulting in higher heat transfer rates for a given pore density, especially when combined with jet configurations with larger open areas. Finally, we evaluated the thermal hydraulic performance for different foam configurations and the optimum value of a given PPI was found to be at an intermediate rather than the lowest foam thickness.

High Porosity and High Pore Density Thin Copper Foams for Compact Electronics Cooling

2018 ◽  
Author(s):  
Sanskar S. Panse ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Metal Foam ◽  
Electronics Cooling ◽  
High Heat ◽  
High Porosity ◽  
Heat Transfer Area ◽  
Pore Density ◽  
Base Surface ◽  
High Heat Transfer

Porous media like open celled metal foams inherently provide a high heat transfer area per unit volume due to their interconnected cellular structure and are lightweight. High pore density metal foam because of its small overall dimensions and micro feature size shows promise in thermal packaging of compact electronics. An experimental study was carried out to evaluate thermal performance of high porosity (95%) and high pore density (90 PPI) copper foam of size 20 mm × 20 mm × 3 mm in buoyancy induced flow conditions and compared with a baseline smooth surface. The enhanced surface showed about 15% enhancement in average heat transfer coefficient over the baseline case. To optimize the performance further, the foam sample was cut into strips of 20 mm × 5 mm × 3 mm and attached symmetrically on the central 20 mm2 base surface area with inter-spacing of 2.5 mm. This new configuration led to further 15% enhancement in heat transfer even with 25% lesser heat transfer area. This is significant as heat transfer is seen as a strong function of permeability to flow through the structure over heat conduction through it. To test this hypothesis, a third configuration was tested in which the strips were further cut into blocks of 4 mm × 4 mm × 3 mm and attached in a 3 × 3 array on to the base surface. Here, only 36% of the central 20 mm2 base surface area was covered with foam. The heat transfer performance was found to be within ± 10% of the initial metal foam configuration, thereby, supporting the hypothesis. Performance was seen to decrease with increase in inclination from 0° to 30° to 90° with respect to the vertical.

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.

scholarly journals Array Jet Impingement On High Porosity Thin Metal Foams: Effect of Foam Height, Pore-Density and Spent Air Crossflow Scheme On Flow Distribution and Heat Transfer

2020 ◽  
Author(s):  
Vivek Subramaniam Sambamurthy ◽  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Flow Distribution ◽  
Jet Impingement ◽  
Metal Foams ◽  
Thin Metal ◽  
High Porosity ◽  
Pore Density ◽  
Pumping Power ◽  
Local Flow ◽  
Target Spacing

Abstract An experimental investigation was carried out to study heat transfer and fluid flow in high porosity (93%) thin metal foams subjected to array jet impingement, under maximum and intermediate crossflow exit schemes. Separate effects of pore-density and jet-to-target spacing (z/d) have been studied. To this end, for a fixed pore-density of 40PPI foams, three different jet-to-target spacing (z/d=1, 2, 6) were investigated, and for a fixed z/d of 6, three different pore-density of 5, 20 and 40PPI were investigated. The jet diameter-based Reynolds number was varied between 3,000-12,000. Experiments were carried out to characterize local flow distribution and Nusselt numbers for different jet impingement configurations. The heat transfer results were obtained through steady-state experiments. Local flow measurements show that, as z/d decreases, the mass flux distributions are increasingly skewed with higher mass flow rates near the exits. Heat transfer enhancement has been calculated and the optimum foam configuration has been deduced from the pumping power. It was observed that Nusselt number increases with increasing pore density at a fixed z/d and reduces with increase in z/d at constant pore density. Intermediate crossflow had higher heat transfer than maximum crossflow with significantly lower pumping power. Under a constant pumping power condition, z/d = 2, 40ppi foam provided an average enhancement of 35% over the corresponding baseline configuration for intermediate crossflow scheme and was found to be the most optimum configuration.

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.

Experimental Investigation of Heat Transfer Enhancement Through Array Jet Impingement on Various Configurations of High Porosity Thin Metal Foams

2018 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Stresses ◽  
Metal Foam ◽  
Jet Impingement ◽  
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 significant increase in wetted surface area as well as highly tortuous flow paths to coolant flowing over fibers. Further, jet impingement is also known to offer high convective cooling, particularly on the footprints of the jets on the target to be cooled. Jet impingement, however, leads to large special gradients in heat transfer coefficient, leading to increased thermal stresses. In this study, we have tried to use high porosity thin metal foams subjected to array jet impingement, for a special crossflow scheme. One aim of using metal foams is to achieve cooling uniformity also, which is tough to achieve for impingement cooling. High porosity (92.65%) and high pore density (40 pores per inch, 3 mm thick) foams have been used as heat transfer enhancement agents. In order to reduce the pumping power requirements imposed by full metal foam design, we developed two striped metal foam configurations. For that, the jets were arranged in 3 × 6 array (x/d = 3.42, y/d = 2), such that the crossflow is dominantly sideways. This crossflow scheme allowed usage of thin stripes, where in one configuration we studied direct impingement onto stripes of metal foam and in the other, we studied impingement onto metal and crossflow interacted with metal foams. Steady state heat transfer experiments have been conducted for a jet plate configuration with varying jet-to-target plate distance z/d = 0.75, 2 and 4. The baseline case was jet impingement onto a smooth target surface. Jet diameter-based Reynolds number was varied between 3000 to 11000. Enhancement in heat transfer due to impingement onto thin metal foams has been evaluated against the enhancement in pumping power requirements. For a specific case of z/d = 0.75 with the base surface fully covered with metal foam, metal foams have enhanced heat transfer by 2.42 times 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.

Numerical Study of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite at Pore Scale

2016 ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Pore Size ◽  
Metal Foam ◽  
Foam Cell ◽  
High Porosity ◽  
Pore Scale ◽  
Thermal Equilibrium State ◽  
Foam Structure ◽  
Open Cell

In this paper, a numerical model employing 3D foam structure represented by Weaire-Phelan foam cell is developed to study the steady heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. Two conduction problems are considered in the cubic representative computation unit of the composite material: one with constant temperature difference between opposite sides of the cubic unit (that can be used to determine the effective thermal conductivity (ETC)) and the second with constant heat flux at the interface between metal foam and paraffin (that can be used to determine the interstitial conduction heat transfer coefficient (ICHTC)). The effects of foam pore structure parameters (pore size and porosity) on heat conduction are investigated for the above two problems. Results show that for the first conduction problem, the effect of foam structure on heat conduction (i.e. the ETC) is related to porosity rather than pore size. The essential reason is due to the thermal equilibrium state between metal foam and paraffin indicated by the negligible interstitial heat transfer. While for the second conduction problem with inherent thermal non-equilibrium effect, it shows that both porosity and pore size significantly influence the interstitial heat conduction (i.e. the ICHTC). Furthermore, the present ETC and ICHTC data are compared to the results in the published literature. It shows that our ETC data agree well with the reported experimental results, and are more accurate than the numerical predications based on body-centered-cubic foam cell in literature. And our ICHTC data are in qualitative agreement with the published numerical results, but the present results are based on a more realistic foam structure.

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