Showing papers on "Thermal contact conductance published in 1983"
272 citations
TL;DR: In this paper, a simple equation enabling the prediction of the thermal conductivity of plastic foams, without the aid of adjustable parameters, is proposed, based on a recurrent method, previously developed, that showed reasonable agreement with experimental results.
Abstract: A simple equation enabling the prediction of the thermal conductivity of plastic foams, without the aid of adjustable parameters, is proposed. The equation is based on a recurrent method, previously developed, that showed reasonable agreement with experimental results. Ways of decreasing the thermal radiation contribution are shown. In particular, the influence of cell size, radiation transmission through solid membranes, and low-emissivity boundary surfaces are analyzed. Errors involved in steady techniques of measuring the thermal conductivity associated with radiation are discussed.
59 citations
TL;DR: In this paper, the authors show that the classical contact theory is inapplicable to small contact spots where the contact spots are small (typically < 0.05 µm in aluminum).
Abstract: The temperature of an electrical contact is usually evaluated from a measurement of the potential drop across the contact through the well-established relation f Tm V2 =8 ~ ~odT. · ' TO and p are, respectively, the thermal conductivity and the electrical resistivity of the junction material; To and Tm are, respectively, the temperature of the junction body and of the contact spot; and V is the potential drop. Experimental evidence is presented which indicates that this relation, and more generally classical Contact theory, is inapplicable to junctions where the contact spots are small (typically <0.05 µm in aluminum). The origin of this breakdown of the theory is explored.
47 citations
TL;DR: In this paper, the thermal conductivity of a two-dimensional lattice with 1000 particles on a triangular lattice interacting via the Lennard-Jones potential was investigated and it was shown that boundary scattering was the dominant resistive mechanism in this case.
Abstract: We have studied steady-state heat flow in a two-dimensional crystal by the method of molecular dynamics. The model system contains 1000 particles on a triangular lattice interacting via the Lennard-Jones potential. The system is 50 unit cells long and 10 unit cells wide. We find that the thermal conductivity $\ensuremath{\kappa}$ of this system is consistent with $\frac{1}{T}$ behavior as expected when phonon-phonon scattering is the dominant mechanism for thermal resistance. We have also carried out similar calculations for three-dimensional Lennard-Jones systems in both fluid and crystalline configurations. The results for the fluid were in good agreement with earlier calculations but for the fcc solid system, 16 unit cells in length, $\ensuremath{\kappa}$ was independent of temperature. We determined that boundary scattering was the dominant resistive mechanism in this case. To escape the boundary-limited regime, the length of the three-dimensional crystal needs to be increased by at least a factor of 3. It is feasible to simulate a system of this size with the use of modern computers.
37 citations
TL;DR: In this paper, a procedure theorique d'optimisation de l'epaisseur d'un materiau d'insertion for minimising the resistance thermique de contact entre des surfaces planes rugueuses is presented.
Abstract: Presentation et verification experimentale d'une procedure theorique d'optimisation de l'epaisseur d'un materiau d'insertion pour minimiser la resistance thermique de contact entre des surfaces planes rugueuses
33 citations
31 citations
10 Jan 1983
26 citations
01 Jul 1983
21 citations
Journal Article•
20 citations
TL;DR: In this article, a unit cell model is proposed to predict the effective thermal conductivity of a granular medium composed of sand particles, a thermal binder, and air, and the model is applied to the design of thermal backfill materials for increasing the heat transfer between the earth and underground heat sources.
TL;DR: In this article, the De Senarmont method is used to measure the anisotropy ratio k 1/k 2 of the thermal conductivity in different directions of an anisotropic solid at room temperature and above.
Abstract: Using the modern methods of radiative temperature measurements a refined De Senarmont method (1848) is developed. It allows the measurement of the anisotropy ratio k1/k2 of the thermal conductivity in different directions 1,2 of an anisotropic solid at room temperature and above. This transient method is especially suited for poor thermal conductors like polymers and does also provide an estimate of the absolute thermal diffusivity.
TL;DR: In this article, simple power-law correlations have been deduced to predict the dependence of non-dimensional thermal contact conductance on the nondimensional contact pressure for Zircaloy-2/uranium dioxide surfaces in contact.
Abstract: Simple power-law correlations have been deduced to predict the dependence of nondimensional thermal contact conductance on the nondimensional contact pressure for Zircaloy-2/uranium dioxide surfaces in contact. These correlations are based on the experimental results of several workers. These results indicate that further experimental work is needed to cover a broader range of pressures and temperatures and to ascertain the effect of mean junction temperature on the thermal contact conductance.
01 Jan 1983
TL;DR: In this article, a thermal conductivity cell is described which can be used to measure the bulk thermal conductivities and the thermal contact resistance of paper and other thin-film materials.
Abstract: A new thermal conductivity cell is described which can be used to measure the bulk thermal conductivity and the thermal contact resistance of paper and other thin‐film materials. The cell incorporates a hydraulic piston which can apply pressures up to 1700 psi to the sample which is situated between the optically flat end faces of two brass columns. By measuring the thermal resistance of paper samples of various thicknesses, it is demonstrated that a pressure of 1700 psi effectively eliminates the thermal contact resistance. By comparing measurements at zero and maximum applied pressure, both the bulk conductivity and the contact resistance can be calculated. This is illustrated with several types of paper. In all cases, there is a qualitative correlation between the measured contact resistance and the surface roughness of the sheet. The technique can also be used for thin polymer films, and for layered structures such as the ink donor films used in thermal transfer printing.
TL;DR: In this article, the effect of ionising radiation on the specific heat, thermal conductivity, thermal diffusivity, and density of partially crystalline (polyethylene, polypropylene, polytetrafluoro-ethylene) and amorphous polymers (polystyrene, poly(methyl methacrylate)) is discussed.
Abstract: The effect of ionising radiation on the specific heat, thermal conductivity, thermal diffusivity, and density of partially crystalline (polyethylene, polypropylene, polytetrafluoro-ethylene) and of amorphous polymers (polystyrene, poly(methyl methacrylate)) is discussed. Analytical models of the mechanism of heat conduction, and the development of anisotropic thermal conductivity in amorphous polymers, are examined. The influence of ionising radiation on the thermophysical properties of composite materials is analysed. 79 references.
01 Jan 1983
TL;DR: In this article, the effects of contact pressure, surface roughness, and surface error-of-form on the contact conductance between depleted uranium dioxide and Zircaloy-4 were investigated using a modified longitudinal design apparatus.
Abstract: A scoping study was performed using a modified longitudinal design apparatus to investigate the effects of contact pressure (0 to 14.68 MN/m2), surface roughness, and surface error-of-form on the contact conductance between depleted uranium dioxide and Zircaloy-4. The results are compared to four existing contact conductance models which assume that the contact conductance depends on the surface roughness and elastic/plastic deformation of surface asperities. The model by Mikic-Todreas was found to best fit the data. It was also found that the pressure exponent depends on the contact pressure, surface roughness, and surface error-of-form rather than being independent of these parameters as assumed by the models. The data is also found to qualitatively fit the model by Dundurs and Panek which thereby suggests that the surface error-of-form may be the predominant factor in predicting the contact conductance, rather than the surface roughness. It is also observed that the fluid (i.e., gas) conductance rather than the contact conductance constituted the major contribution to the total interface conductance in the contact pressure range studied.
10 Jan 1983
11 Jul 1983
01 Jan 1983
TL;DR: In this article, a scaled fundamental equation for the thermodynamic properties in the critical region and a relationship between the equation of state and the scale factor of the correlation length is presented.
Abstract: A progress report towards formulating an accurate description of the critical thermal conductivity enhancement of fluids is presented. The improved formulation presented in this paper is based on a scaled fundamental equation for the thermodynamic properties in the critical region and a relationship between the equation of state and the scale factor of the correlation length which characterizes the range of the critical fluctuations. As an example, we consider carbon dioxide for which a considerable amount of experimental evidence is available.
01 May 1983
TL;DR: In this paper, the thermal contact conductance of a 0.4 micrometer surface finish OFHC copper sample pair has been investigated from 1.6 to 3.8 K for a range of applied contact forces up to 670 N.
Abstract: The thermal contact conductance of a 0.4 micrometer surface finish OFHC copper sample pair has been investigated from 1.6 to 3.8 K for a range of applied contact forces up to 670 N. Experimental data have been fitted to the relation Q = the integral alpha T to the nth power dt by assuming that the thermal contact conductance is a simple power function of the sample temperature. It has been found that the conductance is proportional to T squared and that conductance increases with an increase in applied contact force. These results confirm earlier work.
TL;DR: In this article, it was shown that the thermal transport in a thin solid specimen under ballistic phonon propagation is as well dictated by the thermal boundary resistances of the relevant interfaces, resulting in an effective thermal conductivity proportional to the thickness of the specimen.
Abstract: The effective thermal conductivity of a rarefied gas bounded by two solid surfaces is shown to be dominated by the two surface thermal resistances. Using an analogous picture, it is demonstrated that the thermal transport in a thin solid specimen under ballistic phonon propagation is as well dictated by the thermal boundary resistances of the relevant interfaces, resulting in an effective thermal conductivity proportional to the thickness of the specimen. The implications of the results are discussed.
TL;DR: In this article, the effect of thermal radiation on measurements of the thermal conductivity of small samples below room temperature was studied and the importance of these effects for temperatures greater than about 100K was measured.
Abstract: The authors have studied the effect of thermal radiation on measurements of the thermal conductivity of small samples below room temperature. By using the different thermal conductivity technique they were able to measure the importance of these effects for temperatures greater than about 100K and to determine the principal source of error of the double flux correction, i.e. the different heater temperature with each different heat flux. They thus propose a better configuration for performing such measurements.
01 Jan 1983
TL;DR: In this article, the authors show that the scheme of equivalent wall for a contact between two solids in a transient thermal state is entirely equivalent to the mode of thermal contact resistance for the usual frequencies.
Abstract: We show that the scheme of «equivalent wall» for a contact between two solids in a transient thermal state is entirely equivalent to the scheme of «thermal contact resistance» for the usual frequencies On montre, pour les frequences realisables en pratique, que le modele du «milieu equivalent» associe a un contact solide-solide en regime variable est totalement equivalent au modele de «resistance de contact»
TL;DR: In this paper, the low-temperature thermal conductivity of two antiferromagnets: CoCO 3 and MnCO 3 has been measured, and it is shown that the scattering of phonons by magnons makes an appreciable contribution to thermal resistance.
01 May 1983
TL;DR: In this paper, the thermal contact conductance of a 0.4 micrometer surface finish OFHC copper sample pair has been investigated from 1.6 to 3.8 K for a range of applied contact forces up to 670 N.
Abstract: The thermal contact conductance of a 0.4 micrometer surface finish OFHC copper sample pair has been investigated from 1.6 to 3.8 K for a range of applied contact forces up to 670 N. Experimental data have been fitted to the relation Q = the integral alpha T to the nth power dt by assuming that the thermal contact conductance is a simple power function of the sample temperature. It has been found that the conductance is proportional to T squared and that conductance increases with an increase in applied contact force. These results confirm earlier work.
01 Jul 1983