Enhancement of Thermal Contact Conductance by Metallic Coatings: Theory and Experiment

1985 ◽  
Vol 107 (3) ◽  
pp. 513-519 ◽  
Author(s):  
V. W. Antonetti ◽  
M. M. Yovanovich
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Glass Bead ◽  
Thermal Contact ◽  
The Other ◽  
Thermal Contact Conductance ◽  
Thermomechanical Model ◽  
Thermal Test ◽  
Test Points ◽  
Theory And Experiment

A thermomechanical model for nominally flat, rough contacting surfaces coated with a metallic layer is developed. The model is shown to agree quite well with thermal test data obtained using nickel specimens, with one side of the contact coated with silver and the other side glass-bead blasted. In addition, it is demonstrated that a coated joint can be reduced to an equivalent bare joint by employing an effective hardness and an effective thermal conductivity. Using this technique, 61 coated test points were correlated, with an RMS difference of ± 12.6 percent between the data and a correlation which had previously been used only for bare contacts.

Influence of Contact Mechanics in the Prediction of the Effective Thermal Conductivity of Spheroid Packed Beds

2003 ◽  
Author(s):  
G. Buonanno ◽  
A. Carotenuto ◽  
G. Giovinco ◽  
L. Vanoli
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Statistical Approach ◽  
Thermal Contact ◽  
Peak Height ◽  
Thermal Contact Conductance ◽  
Curvature Radius ◽  
Packed Beds ◽  
Wide Range ◽  
Thermal Phenomena

Thermal contact conductance is an important parameter in a wide range of thermal phenomena, and consequently a large number of experimental, numerical and statistical investigations have been carried out in literature. In the present paper an analysis of thermal contact resistance is carried out to predict heat transfer between spherical rough surfaces in contact, by means of a statistical approach. The micro-geometry of the surface is described through a probabilistic model based on the peak height variability and invariant asperity curvature radius. The numerical model has been applied to evaluate the effective thermal conductivity of packed beds of steel spheroids and validated through the comparison with the experimental data obtained by means of an apparatus designed and build up for this purpose.

Measurement of the Thermal Contact Conductance and Thermal Conductivity of Anodized Aluminum Coatings

1990 ◽  
Vol 112 (3) ◽  
pp. 579-585 ◽  
Author(s):  
G. P. Peterson ◽  
L. S. Fletcher
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Coating Thickness ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Aluminum Surface ◽  
Anodized Aluminum ◽  
Contact Conductance ◽  
Surface Measurements

An experimental investigation was conducted to determine the thermal contact conductance and effective thermal conductivity of anodized coatings. One chemically polished Aluminum 6061-T6 test specimen and seven specimens with anodized coatings varying in thickness from 60.9 μm to 163.8 μm were tested while in contact with a single unanodized aluminum surface. Measurements of the overall joint conductance, composed of the thermal contact conductance between the anodized coating and the bare aluminum surface and the bulk conductance of the coating material, indicated that the overall joint conductance decreased with increasing thickness of the anodized coating and increased with increasing interfacial load. Using the experimental data, a dimensionless expression was developed that related the overall joint conductance to the coating thickness, the surface roughness, the interfacial pressure, and the properties of the aluminum substrate. By subtracting the thermal contact conductance from the measured overall joint conductance, estimations of the effective thermal conductivity of the anodized coating as a function of pressure were obtained for each of the seven anodized specimens. At an extrapolated pressure of zero, the effective thermal conductivity was found to be approximately 0.02 W/m-K. In addition to this extrapolated value, a single expression for predicting the effective thermal conductivity as a function of both the interface pressure and the anodized coating thickness was developed and shown to be within ±5 percent of the experimental data over a pressure range of 0 to 14 MPa.

Thermal Contact Conductance of a Bone-Dry Paper Handsheet/Metal Interface

1992 ◽  
Vol 114 (2) ◽  
pp. 326-330 ◽  
Author(s):  
J. Seyed-Yagoobi ◽  
K. H. Ng ◽  
L. S. Fletcher
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Water Retention ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Metal Interface ◽  
Contact Conductance ◽  
Interface Contact ◽  
Sheet Density

An apparatus was constructed for determination of the thermal contact conductance for a paper handsheet/metal interface and for measurement of the effective thermal conductivity of handsheet samples. Bone-dry Bleached Southern Mixed Kraft hand-sheets with a water retention value of 1.832 were used to study the effect of pressure on thermal contact conductance and to measure the effective thermal conductivity of samples at various sheet density levels. A regression model describing the interface thermal contact conductance as a function of pressure and basis weight was derived. The contact conductance increases with increasing pressure or with decreasing basis weight. At a pressure of 2.3 kPa, the value of the interface contact conductance for the bone-dry samples considered ranges from approximately 97 W/m2K for a sheet of 348.7 g/m2 basis weight to 200 W/m2K for a sheet of 68.0 g/m2 basis weight. For pressures near 300 kPa, these values increase to 146 and 452 W/m2K, respectively. The effective thermal conductivity of the handsheet samples was derived from measured values of overall joint conductance and interface contact conductance. The results indicate that the thermal conductivity of the bone-dry samples increases with increasing sheet density, ranging from 0.14 W/mK to 0.70 W/mK for sheet densities of 90 kg/m3 to 500 kg/m3, respectively, for the samples considered.

scholarly journals Microstructure Dependence of Effective Thermal Conductivity of EB-PVD TBCs

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1838
Author(s):  
Shi-Yi Qiu ◽  
Chen-Wu Wu ◽  
Chen-Guang Huang ◽  
Yue Ma ◽  
Hong-Bo Guo
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Stress ◽  
Effective Thermal Conductivity ◽  
Thermal Insulation ◽  
Inclination Angle ◽  
Physical Vapor Deposition ◽  
Thermal Contact ◽  
Mathematic Model ◽  
Columnar Structure ◽  
Structural Parameter

Microstructure dependence of effective thermal conductivity of the coating was investigated to optimize the thermal insulation of columnar structure electron beam physical vapor deposition (EB-PVD coating), considering constraints by mechanical stress. First, a three-dimensional finite element model of multiple columnar structure was established to involve thermal contact resistance across the interfaces between the adjacent columnar structures. Then, the mathematical formula of each structural parameter was derived to demonstrate the numerical outcome and predict the effective thermal conductivity. After that, the heat conduction characteristics of the columnar structured coating was analyzed to reveal the dependence of the effective thermal conductivity of the thermal barrier coatings (TBCs) on its microstructure characteristics, including the column diameter, the thickness of coating, the ratio of the height of fine column to coarse column and the inclination angle of columns. Finally, the influence of each microstructural parameter on the mechanical stress of the TBCs was studied by a mathematic model, and the optimization of the inclination angle was proposed, considering the thermal insulation and mechanical stress of the coating.

Effective Thermal Conductivity of Composites Reinforced with Curvilinearly Anisotropic Inclusions with Kapitza Contact Resistance

2006 ◽  
Vol 306-308 ◽  
pp. 775-780
Author(s):  
Tung Yang Chen
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Closed Form ◽  
Effective Thermal Conductivity ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Transversely Isotropic ◽  
Closed Form Expression ◽  
Form Expression ◽  
Micromechanical Models

Effective thermal conductivities of composites consisting of curvilinearly anisotropic inclusions with Kapitza thermal contact resistance between the constituents are considered. We show that the effect of these curvilinearly anisotropic inclusions can be exactly simulated by certain equivalent isotropic or transversely isotropic inclusions. Three different micromechanical models are employed to estimate the effective thermal conductivity of the composite. Interestingly, all these methods result in the same simple, closed-form expression.

Numerical Simulations of Thermal Transport in Random Porous Materials and Powder Systems Using the Smoothed Particle Hydrodynamics Method

2017 ◽  
Author(s):  
Deepak Shah ◽  
Alexey N. Volkov
Keyword(s):  
Thermal Conductivity ◽  
Porous Materials ◽  
Effective Thermal Conductivity ◽  
Smoothed Particle Hydrodynamics ◽  
Thermal Transport ◽  
Thermal Contact Conductance ◽  
Powder Bed ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Powder Particles

A numerical method to solve thermal transport problems in powder bed systems and porous materials with finite thermal contact conductance at interfaces between individual powder particles or grains is developed based on the Smoothed Particle Hydrodynamics approach. The developed method is applied to study the effective thermal conductivity of two-dimensional random powder bed systems with binary distribution of powder particles radii. The effects of particle size distribution parameters, density parameter, and effective interface area between particles on the effective thermal conductivity are studied. It is found that at finite Biot number, which characterizes the ratio of the interfacial conductance to the conductance of the bulk powder material, the effective thermal conductivity of porous samples increases with increasing fraction of particles of larger size.

Thermal Contact Resistance at a Metal Foam-Solid Surface Interface

2011 ◽  
Author(s):  
Ehsan Sadeghi ◽  
Scott Hsieh ◽  
Majid Bahrami
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Contact Area ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Metal Foams ◽  
Real Contact Area ◽  
The Real ◽  
Real Contact

Accurate information on heat transfer and temperature distribution in metal foams is necessary for design and modeling of thermal-hydraulic systems incorporating metal foams. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the metal foams and adjacent surfaces/layers. In the present study, a test bed that allows the separation of effective thermal conductivity and thermal contact resistance in metal foams is described. Measurements are performed in a vacuum under varying compressive loads using ERG Duocel aluminum foam samples with different porosities and pore densities. Also, a graphical method associated with a computer code is developed to demonstrate the distribution of contact spots and estimate the real contact area at the interface. Our results show that the porosity and the effective thermal conductivity remain unchanged with the variation of compression in the range of 0 to 2 MPa; but TCR decreases significantly with pressure due to an increase in the real contact area at the interface. Moreover, the ratio of real to nominal contact area varies between 0 to 0.013, depending upon the compressive force, porosity, and surface characteristics.

scholarly journals Measurement of the Thermophysical Properties of Anisotropic Insulation Materials with Consideration of the Effect of Thermal Contact Resistance

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1353 ◽  
Author(s):  
Dongxu Han ◽  
Kai Yue ◽  
Liang Cheng ◽  
Xuri Yang ◽  
Xinxin Zhang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Maximum Deviation ◽  
Insulation Materials ◽  
Steady State Method ◽  
Different Temperatures

A novel method involving the effect of thermal contact resistance (TCR) was proposed using a plane heat source smaller than the measured samples for improving measurement accuracy of the simultaneous determination of in-plane and cross-plane thermal conductivities and the volumetric heat capacity of anisotropic materials. The heat transfer during the measurement process was mathematically modeled in a 3D Cartesian coordinate system. The temperature distribution inside the sample was analytically derived by applying Laplace transform and the variables separation method. A multiparameter estimation algorithm was developed on the basis of the sensitivity analysis of the parameters to simultaneously estimate the measured parameters. The correctness of the algorithm was verified by performing simulation experiments. The thermophysical parameters of insulating materials were experimentally measured using the proposed method at different temperatures and pressures. Fiber glass and ceramic insulation materials were tested at room temperature. The measured results showed that the relative error was 1.6% less than the standard value and proved the accuracy of the proposed method. The TCRs measured at different pressures were compared with those obtained using the steady-state method, and the maximum deviation was 8.5%. The thermal conductivity obtained with the contact thermal resistance was smaller than that without the thermal resistance. The measurement results for the anisotropic silica aerogels at different temperatures and pressures revealed that the thermal conductivity and thermal contact conductance increased as temperature and pressure increased.

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