Numerical assessment of thermal characteristics of metal foams of orderly varied pore density and porosity under different convection regimes

2022 ◽  
Vol 172 ◽  
pp. 107288
Author(s):  
Trilok G ◽  
K. Kiran Kumar ◽  
N. Gnanasekaran ◽  
Moghtada Mobedi
Author(s):  
M. Oliviero ◽  
S. Cunsolo ◽  
W. M. Harris ◽  
M. Iasiello ◽  
W. K. S. Chiu ◽  
...  

Their light weight, open porosity, high surface area per unit volume and thermal characteristics make metal foams a promising material for many industrial applications involving fluid flow and heat transfer. Pressure drop and heat transfer of porous media have inspired a number of experimental and numerical studies. Many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models. Most studies are based on idealized periodic cell structures. In this study, the true 3-D micro-structure of the metal foam is obtained by employing x-ray computed microtomography (XCT). For comparison, ideal Kelvin foam structures are developed in the free-to-use software “Surface Evolver” surface energy minimization program. Pressure drop and heat transfer are then investigated using the CFD Module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out.


2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Ninad Trifale ◽  
Eric Nauman ◽  
Kazuaki Yazawa

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.


Author(s):  
Han Shen ◽  
Xueting Liu ◽  
Hongbin Yan ◽  
Gongnan Xie ◽  
Bengt Sunden

Internal Y-shaped bifurcation has been proved to be an advantageous way on improving thermal performance of microchannel heat sinks according to the previous research. Metal foams are known due to their predominate performance such as low-density, large surface area, and high thermal conductivity. In this paper, different parameters of metal foams in Y-shaped bifurcation microchannel heat sinks are designed and investigated numerically. The effects of Reynolds number, porosity of metal foam, and the pore density (PPI) of the metal foam on the microchannel heat sinks are analyzed in detail. It is found that the internal Y-shaped bifurcation microchannel heat sinks with metal foam exhibit better heat transfer enhancement and overall thermal performance. This research provides broad application prospects for heat sinks with metal foam in the thermal management of high power density electronic devices.


Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8343
Author(s):  
Trilok G ◽  
N Gnanasekaran ◽  
Moghtada Mobedi

The long standing issue of increased heat transfer, always accompanied by increased pressure drop using metal foams, is addressed in the present work. Heat transfer and pressure drop, both of various magnitudes, can be observed in respect to various flow and heat transfer influencing aspects of considered metal foams. In this regard, for the first time, orderly varying pore density (characterized by visible pores per inch, i.e., PPI) and porosity (characterized by ratio of void volume to total volume) along with varied thickness are considered to comprehensively analyze variation in the trade-off scenario between flow resistance minimization and heat transfer augmentation behavior of metal foams with the help of numerical simulations and TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) which is a multi-criteria decision-making tool to address the considered multi-objective problem. A numerical domain of vertical channel is modelled with zone of metal foam porous media at the channel center by invoking LTNE and Darcy–Forchheimer models. Metal foams of four thickness ratios are considered (1, 0.75, 0.5 and 0.25), along with varied pore density (5, 10, 15, 20 and 25 PPI), each at various porosity conditions of 0.8, 0.85, 0.9 and 0.95 porosity. Numerically obtained pressure and temperature field data are critically analyzed for various trade-off scenarios exhibited under the abovementioned variable conditions. A type of metal foam based on its morphological (pore density and porosity) and configurational (thickness) aspects, which can participate in a desired trade-off scenario between flow resistance and heat transfer, is illustrated.


2020 ◽  
Author(s):  
Vivek Subramaniam Sambamurthy ◽  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad

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.


Author(s):  
Srivatsan Madhavan ◽  
Vivek Subramaniam Sambamurthy ◽  
Prashant Singh ◽  
Srinath Ekkad

Abstract Array jet impingement heat transfer onto thin metal foams of different pore densities has been experimentally investigated in the current study. Aluminum foams with high porosity (93%) and different pore densities of 5, 20 and 40 ppi are subjected to array jet impingement under an intermediate crossflow exit scheme. The jets are arranged such that the streamwise jet-to-jet spacing is x/dj = 8 and spanwise jet-to-jet spacing is y/dj = 4. Jet to target plate spacing was maintained at z/dj = 6 where ‘z’ is the distance between the jet plate and the target surface on which metal foams were installed. A steady state heat transfer technique has been used to obtain local heat transfer coefficients along the streamwise direction. It is observed that heat transfer enhancement levels increase as pore density increases. An enhancement of 50–100% over the baseline case of impingement onto smooth surface is obtained over the flow range tested (3000 < Redj < 12000). At a constant pumping power of 40 W, an enhancement of 26–33% is obtained for the different pore densities tested.


2013 ◽  
Vol 37 (3) ◽  
pp. 841-850 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Sheng-Chung Tzeng ◽  
Zhi-Ting Yeh

This study experimentally investigated the free convection heat transfer characteristics of the annular metal-foam heat sinks. The results showed that the heat transfer coefficient (h) decreased as the pore density of metal foams increased when the thickness (tc) of the annular metal foams equaled 5 mm, but the (h) increased as the pore density increased when tc = 11 and 14.5 mm. Besides, the (h) increased firstly and then decreased as (tc) increased. There was better heat transfer effect when tc = 11 mm in the present study.


Author(s):  
Han Shen ◽  
Xueting Liu ◽  
Bengt Sunden ◽  
Gongnan Xie

Internal Y-shaped bifurcation has been proved to be an advantageous way on improving thermal performance of microchannel heat sinks according to the previous research. Metal foams are known due to their predominate performance such as low-density, large surface area and high thermal conductivity. In this paper, different parameters of metal foams in Y-shaped bifurcation microchannel heat sinks are designed and investigated numerically. The effects of Reynolds number, porosity of metal foam, and the pore density (PPI) of the metal foam on the microchannel heat sinks are analyzed in detail. It is found that the internal Y-shaped bifurcation microchannel heat sinks with metal foam exhibit better heat transfer enhancement and overall thermal performance. This research provides broad application prospects for heat sinks with metal foam in the thermal management of high power density electronic devices.


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