scholarly journals Open-Cell Aluminum Foams by the Sponge Replication Technique

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3840 ◽  
Author(s):  
Sutygina ◽  
Betke ◽  
Scheffler
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Thermal Processing ◽  
Total Porosity ◽  
Lower Amount ◽  
Processing Conditions ◽  
Aluminum Foams ◽  
Open Cell ◽  
Thermally Processed ◽  
Replication Technique

Open-cell aluminum foams were manufactured by a sponge replication technique having a total porosity of ~90%. The influence of the thermal processing conditions such as atmosphere and temperature on the cellular structure, phase composition porosity, thermal conductivity, and compressive strength of the foams was studied. It was found that the thermal processing of aluminum foams in Ar at temperatures up to 800 °C led to aluminum foams with a reduced strut porosity, a lower amount of aluminum oxide, a higher thermal conductivity, and a higher compression strength, compared to foams thermally processed in air. These results were explained by the lower amount of aluminum oxide after thermal processing of the foams.

Convective Heat Transfer Analysis of Open Cell Metal Foam for Solar Air Heaters

Solar Energy ◽  
2003 ◽  
Author(s):  
Nihad Dukhan ◽  
Pablo D. Quinones
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Metal Foam ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Aluminum Foams ◽  
Maximum Heat ◽  
Open Cell ◽  
Maximum Heat Transfer

A one-dimensional heat transfer model for open-cell metal foam is presented. Three aluminum foams having different areas, relative densities, ligament diameters, and number of pores per inch were analyzed. The effective thermal conductivity and the heat transfer increased with the number of pores per inch. The effective thermal conductivity of the foams can be up to four times higher than that of solid aluminum. The resulting improvement in heat transfer can be as high as 50 percent. The maximum heat transfer for the aluminum foams occurs at a pore Reynolds number of 52. The heat transfer, in addition, becomes insensitive to the flow regime for pore Reynolds numbers beyond 200.

Microstructural Modification of Laser-Bent Open-Cell Aluminum Foams

2012 ◽  
Vol 504-506 ◽  
pp. 1213-1218 ◽  
Author(s):  
Loredana Santo ◽  
Denise Bellisario ◽  
Ludovica Rovatti ◽  
Fabrizio Quadrini
Keyword(s):  
Laser Heating ◽  
Laser Power ◽  
Laser Forming ◽  
Processing Conditions ◽  
Aluminum Foams ◽  
Laser Bending ◽  
Bending Angle ◽  
Open Cell ◽  
Scan Rate ◽  
Alloy Microstructure

Laser forming tests have been performed on open-cell aluminum alloy foams with different pore size. Laser power was fixed at 150 W, a total of 150 laser scans led to a bending angle up to 60°, depending on the laser scan rate. At the end of the laser bending, the foams were left to cool and samples were extracted for analysis by means of an optic microscope. The alloy microstructure was investigated in different points of the samples and correlated with the processing conditions. Image analysis was also carried out to extract the percentage of melted area due to laser heating.

scholarly journals Open-Cellular Alumina Foams with Hierarchical Strut Porosity by Ice Templating: A Thickening Agent Study

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1060
Author(s):  
Kathleen Dammler ◽  
Katja Schelm ◽  
Ulf Betke ◽  
Tobias Fey ◽  
Michael Scheffler
Keyword(s):  
Thermal Processing ◽  
Freeze Drying ◽  
Volume Ratio ◽  
Total Porosity ◽  
Flow Properties ◽  
Ceramic Foams ◽  
Freeze Dried ◽  
Solid Load ◽  
Replication Technique ◽  
Ice Templating

Alumina replica foams were manufactured by the Schwartzwalder sponge replication technique and were provided with an additional strut porosity by a freeze-drying/ice-templating step prior to thermal processing. A variety of thickeners in combination with different alumina solid loads in the dispersion used for polyurethane foam template coating were studied. An additional strut porosity as generated by freeze-drying was found to be in the order of ~20%, and the spacings between the strut pores generated by ice-templating were in the range between 20 µm and 32 µm. In spite of the lamellar strut pore structure and a total porosity exceeding 90%, the compressive strength was found to be up to 1.3 MPa. Combining the replica process with freeze-drying proves to be a suitable method to enhance foams with respect to their surface area accessible for active coatings while preserving the advantageous flow properties of the cellular structure. A two-to-threefold object surface-to-object volume ratio of 55 to 77 mm−1 was achieved for samples with 30 vol% solid load compared to 26 mm−1 for non-freeze-dried samples. The freeze-drying technique allows the control of the proportion and properties of the introduced pores in an uncomplicated and predictable way by adjusting the process parameters. Nevertheless, the present article demonstrates that a suitable thickener in the dispersion used for the Schwartzwalder process is inevitable to obtain ceramic foams with sufficient mechanical strength due to the necessarily increased water content of the ceramic dispersion used for foam manufacturing.

scholarly journals Effective Thermal Conductivity of Open Cell Polyurethane Foam Based on the Fractal Theory

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Kan Ankang ◽  
Han Houde
Keyword(s):  
Thermal Conductivity ◽  
Fractal Dimension ◽  
Effective Thermal Conductivity ◽  
Polyurethane Foam ◽  
Solid Phase ◽  
Fractal Theory ◽  
Heat Radiation ◽  
Total Thermal Conductivity ◽  
Equivalent Thermal Conductivity ◽  
Open Cell

Based on the fractal theory, the geometric structure inside an open cell polyurethane foam, which is widely used as adiabatic material, is illustrated. A simplified cell fractal model is created. In the model, the method of calculating the equivalent thermal conductivity of the porous foam is described and the fractal dimension is calculated. The mathematical formulas for the fractal equivalent thermal conductivity combined with gas and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity, are deduced. However, the total effective heat flux is the summation of the heat conduction by the solid phase and the gas in pores, the radiation, and the convection between gas and solid phase. Fractal mathematical equation of effective thermal conductivity is derived with fractal dimension and vacancy porosity in the cell body. The calculated results have good agreement with the experimental data, and the difference is less than 5%. The main influencing factors are summarized. The research work is useful for the enhancement of adiabatic performance of foam materials and development of new materials.

Evaluation of the Temperature Oscillation Technique to Calculate Thermal Conductivity of Water and Systematic Measurement of the Thermal Conductivity of Aluminum Oxide – Water Nanofluid

2004 ◽  
Author(s):  
P. Bhattacharya ◽  
S. Nara ◽  
P. Vijayan ◽  
T. Tang ◽  
W. Lai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Effective Thermal Conductivity ◽  
Base Fluid ◽  
Suspended Solid ◽  
Temperature Oscillation ◽  
Solid Particles ◽  
Systematic Measurement ◽  
Experimental Setup ◽  
Suspended Solid Particles

A nanofluid is a fluid containing suspended solid particles, with sizes of the order of nanometers. The nanofluids are better conductors of heat than the base fluid itself. Therefore it is of interest to measure the effective thermal conductivity of such a nanofluid. We use temperature oscillation technique to measure the thermal conductivity of the nanofluid. However, first we evaluate the temperature oscillation technique as a tool to measure thermal conductivity of water. Then we validate our experimental setup by measuring the thermal conductivity of the aluminum oxide-water nanofluid and comparing our results with previously published work. Finally, we do a systematic series of measurements of the thermal conductivities of aluminum oxide-water nanofluids at various temperatures and explain the reasons behind the dependence of the enhancement in thermal conductivity of the nanofluid on temperature.

scholarly journals Estimation of thermal conductivity of short pastry biscuit at different baking stages

2014 ◽  
Vol 45 (2) ◽  
pp. 64 ◽  
Author(s):  
Chiara Cevoli ◽  
Angelo Fabbri ◽  
Simone Virginio Marai ◽  
Enrico Ferrari ◽  
Adriano Guarnieri
Keyword(s):  
Thermal Conductivity ◽  
Thermal Processing ◽  
Physical Property ◽  
Physical Models ◽  
Hot Wire ◽  
Line Heat Source ◽  
Food Material ◽  
Wire Method ◽  
Thermal Conductivity Probe

Thermal conductivity of a food material is an essential physical property in mathematical modelling and computer simulation of thermal processing. Effective thermal conductivity of non-homogeneous materials, such as food matrices, can be determined experimentally or mathematically. The aim of the following research was to compare the thermal conductivity of short pastry biscuits, at different baking stages (60-160 min), measured by a line heat source thermal conductivity probe and estimated through the use of thermo-physical models. The measures were carried out on whole biscuits and on powdered biscuits compressed into cylindrical cases. Thermal conductivity of the compacted material, at different baking times (and, consequently at different moisture content), was then used to feed parallel, series, Krischer and Maxwell-Eucken models. The results showed that the application of the hot wire method for the determination of thermal conductivity is not fully feasible if applied directly to whole materials due to mechanical changes applied to the structure and the high presence of fats. The method works best if applied to the biscuit component phases separately. The best model is the Krischer one for its adaptability. In this case the value of biscuit thermal conductivity, for high baking time, varies from 0.15 to 0.19 Wm<sup>–1</sup> K<sup>–1</sup>, while the minimum, for low baking time, varies from 0.11 to 0.12 Wm<sup>–1</sup> K<sup>–1</sup>. These values are close to that reported in literature for similar products.

Influence of Thermal Processing Conditions on Acrylamide Generation and Browning in a Potato Model System

2006 ◽  
Vol 54 (16) ◽  
pp. 5910-5916 ◽  
Author(s):  
Thomas M. Amrein ◽  
Anita Limacher ◽  
Béatrice Conde-Petit ◽  
Renato Amadò ◽  
Felix Escher
Keyword(s):  
Thermal Processing ◽  
Model System ◽  
Processing Conditions
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