Characterization Of The Heat TransferIn Open-cell Metal Foam (original) (raw)
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Experimental and numerical analysis of one dimensional heat transfer on open cell aluminum foams
Gazi University Journal of Science
In this study, one dimensional heat transfer of open cell aluminum metal foams is investigated both experimentally and by using numerical methods as well. Open cell aluminum foams with pore densities of 10, 20 and 30 (Number of Pores Per Inch) PPI were shaped into heat exchangers. The foams having sizes of 200 × 100 × 20 mm were insulated on their three faces. Steady heat flux was maintained on the base section of the foam by heating a plate shaped coil electrically. Temperature distributions on the vertical sections and mostly on locations near heaters were measured with the thermocouples located on the aluminum foams. With the help of the recorded temperatures from the tests the graphs of open cell aluminum foams with pore densities of 10, 20 and 30 were plotted. First of all, one dimensional heat transfer equations were derived for the numerical solution of the system. The governing equations obtained were then discretized by using the Central Difference Method and finally solved...
One-dimensional heat transfer analysis in open-cell 10-ppi metal foam
International Journal of Heat and Mass Transfer, 2005
A one-dimensional heat transfer model for open-cell metal foam is presented. The model combines the conduction in the ligaments and the convection to the coolant in the pores. The approach avoids a complete three-dimensional modeling of the complex flow and heat transfer inside the foam. The temperature along the foam decayed exponentially with the distance from the heated base. The model and the one-dimensional assumption were verified by direct experiment on a thin aluminum foam sample of ten pores per inch for a range of pore Reynolds number. Good agreement was found between the analytical and the experimental results.
Thermal behavior of open cell aluminum foams in forced air: Experimental analysis
This paper deals with the study of thermal and fluid dynamics properties of the open cell metal foams. A thermo-fluid dynamic analysis of three different types of aluminum alloy foams, 5, 10 and 20 pores per inch (PPI) was carried out by using a novel ad hoc built instrumentation. In particular, it has been investigated the Heat Transfer Coefficient (HTC * ) and the Pressure Drop (PD) under a flow of forced humid air. The influence of the main parameters, temperature of the metal foam and speed of humid air, both on the HTC * and on the PD was examined. Design of experiments (DOE) approach was used as support to interpret the experimental findings and the physical phenomena involved in HTC * and in PD, between foams and air. The analysis permitted to detect the effects of the operational parameters, foam pore size, air flux and temperature on the HTC * and on the PD.
Foam height effects on heat transfer performance of 20 ppi aluminum foams
Applied Thermal Engineering, 2012
This paper investigates the heat transfer performance of two 20 PPI (pores per linear inch) aluminum foams with constant porosity (around 0.93) and different foam core height (20 mm and 40 mm). The aluminum foams are cellular structure materials that present a stochastic interconnected pores distribution mostly uniform in size and shape. Most commercially available metal foams are based on aluminum, copper, nickel and metal alloys. Metal foams have considerable applications in multifunctional heat exchangers, cryogenics, combustion chambers, cladding on buildings, strain isolation, petroleum reservoirs, compact heat exchangers for airborne equipment, air cooled condensers and compact heat sinks for power electronics. The experimental measurements of the heat transfer coefficient and pressure drop have been carried out in a test apparatus built at Dipartimento di Fisica Tecnica of the Università di Padova. The foam core height effects on the heat transfer performance have been studied imposing three constant specific heat fluxes at the bottom of the samples: 25.0, 32.5 and 40.0 kW m À2 and varying the frontal air velocity between 2.0 and 5.0 m s À1 . The experimental heat transfer coefficients and pressure gradients have been compared against the predictions obtained from two models recently suggested by present authors.
Heat Transfer Engineering, 2015
Aluminum foams are favorable in modern thermal engineering applications because of the high thermal conductivity and the large specific surface area. The present study is to investigate an application of a porous aluminum foam by using local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) heat transfer models. Threedimensional simulations of laminar flow (for porous foam zone), turbulent flow (for open zone) and heat transfer are performed by a computational fluid dynamics (CFD) approach. Meanwhile, the Forchheimer extended Darcy's law is employed for evaluating the fluid characteristics. The simulation results are compared with the experimental data in the literature. By comparing and analyzing the local and average Nusselt number, it is found that the LTNE and LTE models can obtain the same Nusselt numbers inside the aluminum foam when the air velocity is high, meaning that the aluminum foam is in a thermal equilibrium state. Besides that, a low interfacial heat transfer coefficient is required for the aluminum foam to reach a thermal equilibrium state as the height of the aluminum foam is increased. This study suggests that the LTE model could be applied to predict the thermal performance for the high fluid velocity case or for the case with large height.
Influence of pore density on thermal development in open-cell metal foam
Experimental Thermal and Fluid Science, 2017
Herein heat transfer measurements due to water flow in commercial open-cell aluminum foam confined by a cylindrical shell, which was heated by a constant heat flux, are described. Two kinds of commercial foam were tested: 10 and 40 pores per inch (ppi). Measurements included wall temperature along flow direction as well as average inlet and outlet temperatures of water. Flow rates ranged from Darcy to Forchheimer regimes. The wall temperature along the foam, as well as the local Nusselt number lucidly displayed thermal entry effects leading to thermal fully-developed ρ density (kg.m-3) Subscripts f fluid b bulk (mean) value e effective w wall Highlights • Nusselt numbers were obtained for Darcy and Forchheimer flows • Thermal entry length was determined and was significant for 10, 20 and 40 ppi • Thermal entry length differs from analytical predictions • Thermal entry length in metal foam is weak function of pore density
The Development of Aluminium Foams for Enhanced Heat Transfer
2017
A novel replication technique for the production of open-celled aluminium foam has recently been devised and is undergoing commercial development by the company Constellium. The technique allows close control over the pore size and shape; a feature that is uncharacteristic of metal foam production methods in general and control to such an extent is unprecedented. The method provides an excellent pathway for the exploration of pore geometry/heat transfer behaviour relations, which is the objective of this study. This also aligns with the commercial goals of Constellium as heat transfer applications have been identified as a key market for their foams. Based on the technique; the focus of this work was the development of a laboratory protocol to allow the production of aluminium foam samples with a range of different mesostructures. The heat transfer behaviour, including permeability, of foams with differing matrix metal, pore size, pore aspect ratio and pore shape were examined under forced convection conditions. Decreasing pore size was found to provide enhanced heat transfer, although for pores <3mm the benefit was outweighed by a large decrease in permeability. Small changes in pore shape as a result of preform compaction during processing may be exploited to provide improved heat transfer without reducing permeability. Elongation of pores provided no enhancement of heat transfer or permeability.
Review of Performance Analysis of Aluminum Foams for Heat Transfer Augmentation
Performance analysis has been carried out to investigate the heat transfer characteristics from aluminium foam sample. The samples will be compared with the parallel plate fin heat transfer augmentation. The samples placed in a forced convection arrangement using a plate heater as a heat source and ambient air as the sink. A constant heat flux will be applied throughout the experiment with specific air velocity as a control parameter. The pore density of aluminium foam is varied in the range of the parameters 10, 20 & 40 pores per inches (PPI). Thermal performance of aluminium foam is evaluated in terms of the Nusselt number and thermal resistance of heat sinks. Further, the performance of each aluminium foam will be evaluated based on a compactness factor and power density.
Thermal development in open-cell metal foam: An experiment with constant wall heat flux
International Journal of Heat and Mass Transfer, 2015
Experimental heat transfer results for a commercial open-cell aluminum foam cylinder heated at the wall by a constant heat flux and cooled by water flow, are presented. The results cover thermal-entry and fully-developed regions. Measurements include wall temperature along flow direction as well as average inlet and outlet temperatures of the water. Flow rates are in the Darcy and non-Darcy (transitional and Forchheimer) regimes. The wall temperature along the foam clearly shows two distinct behaviors related to thermally-developing and fully-developed conditions, which is confirmed by the behavior of local Nusselt number. The thermal entry length is determined and discussed in detail; it is also compared to its analytical counterpart for Darcy flow. The thermal entry region in metal foam is found to be significant and much longer than its analytically-predicted value. A method for estimating the bulk fluid temperature is envisioned for calculating the local Nusselt number. Previously undiscussed phenomenon is captured in the behavior of Nusselt number for non-Darcy regimes, which suggests periodic thermal development along the foam. The fully-developed data for the Darcy flow cases is compared to its analytical counterpart, and a correlation for the Nusselt number as a function of Reynolds number is proposed for non-Darcy flows.
Thermal Convection Measurements inside Aluminum Foam and Comparison to Existing Analytical Solutions
Procedia Materials Science, 2014
Metal foams have high thermal conductivity and large surface area per unit volume. The internal structure of the foams promotes vigorous mixing of a moving fluid inside the foams. As such, metal foams are very suited for convection heat transfer designs. Clear models for forced convection heat transfer inside the foam, as well as reliable thermal measurements are indispensable for convection-based thermal system designs. This paper present direct experiment for Darcy airflow and fluid's temperature inside a heated aluminum cylinder filled with aluminum foam. The experimental fluid temperature is compared to the available analytical solutions for the two-equation model for fully-developed forced convection. Peculiar, physically-unexplainable behavior is displayed when plotting the existing analytical solution in the literature. An error was discovered and corrected. Good agreement is obtained with the correct solution.