Thermal Contact Conductance of Spherical Rough Metals

1997 ◽  
Vol 119 (4) ◽  
pp. 684-690 ◽  
Author(s):  
M. A. Lambert ◽  
L. S. Fletcher
Keyword(s):  
Nuclear Reactor ◽  
Combustion Engine ◽  
Fundamental Problem ◽  
Thermal Contact ◽  
Thermal Conductance ◽  
Thermal Control ◽  
Cryogenic Liquid ◽  
Thermal Contact Conductance ◽  
Thermomechanical Model ◽  
Contact Conductance

Junction thermal conductance is an important consideration in such applications as thermally induced stresses in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, gas turbine and internal combustion engine cooling, and cryogenic liquid storage. A fundamental problem in analyzing and predicting junction thermal conductance is determining thermal contact conductance of nonflat rough metals. Workable models have been previously derived for the limiting idealized cases of flat, rough, and spherical smooth surfaces. However, until now no tractable models have been advanced for nonflat rough “engineering” surfaces which are much more commonly dealt with in practice. The present investigation details the synthesis of previously derived models for macroscopically nonuniform thermal contact conductance and contact of nonflat rough spheres into a thermomechanical model, which is presented in an analytical/graphical format. The present model agrees well with representative experimental conductance results from the literature for stainless steel 303 and 304 with widely varying nonflatness (2 to 200 μm) and roughness (0.1 to 10 μm).

Thermal Contact Conductance of Non-Flat, Rough, Metallic Coated Metals

2002 ◽  
Vol 124 (3) ◽  
pp. 405-412 ◽  
Author(s):  
M. A. Lambert ◽  
L. S. Fletcher
Keyword(s):  
Empirical Model ◽  
Nuclear Reactor ◽  
Combustion Engine ◽  
Thermal Contact ◽  
Theoretical Models ◽  
Thermal Control ◽  
Experimental Results ◽  
Thermal Contact Conductance ◽  
Contact Conductance ◽  
Semi Empirical

Thermal contact conductance is an important consideration in such applications as nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling. In many instances, the highest possible thermal contact conductance is desired. For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance. O’Callaghan et al. (1981) as well as Antonetti and Yovanovich (1985, 1988) developed theoretical models for thermal contact conductance of metallic coated metals, both of which have proven accurate for flat, rough surfaces. However, these theories often substantially overpredict the conductance of non-flat, rough, metallic coated metals. In the present investigation, a semi-empirical model for flat and non-flat, rough, uncoated metals, previously developed by Lambert and Fletcher (1996), is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals. The models of Antonetti and Yovanovich (1985, 1988) and Lambert and Fletcher (1996) are compared to experimental data from a number of investigations in the literature. This entailed analyzing the results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness. Both models agree well with experimental results for flat, rough, metallic coated metals. However, the semi-empirical model by Lambert and Fletcher (1996) is more conservative than the theoretical model by Antonetti and Yovanovich (1985, 1988) when compared to the majority of experimental results for non-flat, rough, metallic coated metals.

Recent Developments in Contact Conductance Heat Transfer

1988 ◽  
Vol 110 (4b) ◽  
pp. 1059-1070 ◽  
Author(s):  
L. S. Fletcher
Keyword(s):  
Heat Transfer ◽  
Thermal Contact ◽  
Thermal Conductance ◽  
Thermal Contact Conductance ◽  
Contact Conductance ◽  
Thermal Rectification ◽  
Numerical Studies ◽  
Wide Range ◽  
Theoretical Investigations ◽  
Recent Developments

The characteristics of thermal contact conductance are increasingly important in a wide range of technologies. As a consequence, the number of experimental and theoretical investigations of contact conductance has increased. This paper reviews and categorizes recent developments in contact conductance heat transfer. Among the topics included are the theoretical/analytical/numerical studies of contact conductance for conforming surfaces and other surface geometries; the thermal conductance in such technological areas as advanced or modern materials, microelectronics, and biomedicine; and selected topics including thermal rectification, gas conductance, cylindrical contacts, periodic and sliding contacts, and conductance measurements. The paper concludes with recommendations for emerging and continuing areas of investigation.

A three-dimensional fractal theory based on thermal contact conductance model of rough surfaces

2017 ◽  
Vol 232 (5) ◽  
pp. 528-539 ◽  
Author(s):  
Yongsheng Zhao ◽  
Cui Fang ◽  
Ligang Cai ◽  
Zhifeng Liu
Keyword(s):  
Rough Surfaces ◽  
Fractal Theory ◽  
Thermal Contact ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Engineering Application ◽  
Thermal Contact Conductance ◽  
Real Contact Area ◽  
Contact Conductance ◽  
Elastic Plastic

The thermal contact conductance is an important problem in the field of heat transfer. In this research, a three-dimensional fractal theory based on the thermal contact conductance model is presented. The topography of the contact surfaces was fractal featured and determined by fractal parameters. The asperities in the microscale were considered as elastic, elastic-plastic, or plastic deformations. The real contact area of the asperities could be obtained based on the Hertz contact theory. It was assumed that the rough contact surface was composed of numerous discrete and parallel microcontact cylinders. Consequently, the thermal contact conductance of the surface roughness was composed of the thermal constriction conductance of microcontacts and the air medium thermal conductance of microgaps. The thermal contact conductance of rough surfaces could be calculated by the microasperities integration. An experimental set-up with annular interface was designed to verify the presented thermal contact conductance model. Three materials were used for the thermal contact conductance analysis with different fractal dimensions D and fractal roughness parameters G. The numerical results demonstrated that the thermal contact conductance could be affected by the elastic-plastic deformation of the asperities and the gap thermal conductance should not be ignored under the lower contact load. The presented model would provide a theoretical basis for thermal transfer engineering application.

Thermal and Electrical Conductance of Pressure Tube/Calandria Tube Interface

2020 ◽  
Author(s):  
Chukwudi Azih ◽  
Reilly MacCoy ◽  
Hazem Mazhar ◽  
Chris Fraser
Keyword(s):  
Heat Transfer ◽  
Thermal Contact ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Pressure Tube ◽  
Thermal Contact Conductance ◽  
Interface Pressure ◽  
Contact Conductance ◽  
Engineered Systems ◽  
Interface Thermal Conductance

Abstract In some engineered systems, the interface thermal conductance is a key parameter that governs the heat transfer behaviour of components in solid-solid contact. For example, in certain postulated accident scenarios for CANDU reactors, the pressure tube (PT) may deform into contact with the calandria tube (CT) to form a more direct path for heat transfer from the fuel to the moderator. There have been no direct measurements of interface thermal conductance in integrated “Contact boiling” experiments designed to mimic this Loss-of-coolant accident (LOCA) scenario due to the geometrical limits of the test components and the cumbersome nature of the instrumentation required to extract contact conductance data. It has been noted that the modelling of the contact conductance is one of the main sources of uncertainty in predicting the outcome of the contact boiling experiments that mimic LOCA scenarios. The present study demonstrated an analogy between the electrical and thermal contact conductance for PT/CT interfaces. The range of interface pressure and interface temperatures studies are selected to match the expected range of conditions during a CANDU LOCA scenario. The experiment setup consists of two sets of specimen representing PT and CT material. The specimen are instrumented with four K-type thermocouples in sequence to capture the temperature gradient imposed via a three-chamber oven. Within a range of interface pressures from 2 to 7 MPa and a temperature range from 510 to 720°C, the analogy is independent of the interface pressure or the load applied. This demonstrates the measurement of the electrical conductance between the PT and CT in contact boiling as a promising technique for obtaining in-situ information on the thermal contact conductance during integrated experiments.

Influence of Contact Pressure on the Thermal Contact Conductance of Layered AA3003 Aluminium

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Contact Pressure ◽  
Thermal Contact ◽  
Thermal Conductance ◽  
Thermal Contact Conductance ◽  
Contact Conductance ◽  
Interface Thermal Resistance ◽  
Measurement Results ◽  
Semi Empirical ◽  
The Relationship

For the optimization of the annealing process of aluminium coils, simulation of the process is often performed. To simulate the process with higher accuracy, reliable input parameters are required and the thermal conductivity (thermal contact conductance) is one of them. In the present study, the thermal conductivity and thermal contact conductance of AA3003 alloy sheets were measured by a steady state comparative longitudinal heat flow method at different contact pressure. To evaluate the thermal conductance at the interface, thermal resistance network model' was applied. In addition, the surface roughness of the sheets was also investigated. Based on the measurement results, the semi-empirical equation for the relationship between thermal contact conductance and contact pressure was obtained

Thermal Contact Resistance Modeling of Non-Flat, Roughened Surfaces With Non-Metallic Coatings

2000 ◽  
Vol 123 (1) ◽  
pp. 11-23 ◽  
Author(s):  
E. E. Marotta ◽  
L. S. Fletcher ◽  
Thomas A. Dietz
Keyword(s):  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Metallic Coatings ◽  
Thermomechanical Model ◽  
Contact Conductance ◽  
Flat Surfaces ◽  
Resistance Modeling ◽  
Aluminum Substrates

Essentially all models for prediction of thermal contact conductance or thermal contact resistance have assumed optically flat surfaces for simplification. A few thermal constriction models have been developed which incorporate uncoated, optically non-flat surfaces based on the bulk mechanical properties of the material. Investigations have also been conducted which incorporate the thermophysical properties of metallic coatings and their effective surface microhardness to predict the overall thermal contact conductance. However, these studies and subsequent models have also assumed optically flat surfaces; thus, the application of these models to optically non-flat, coated surface conditions is not feasible without modifications. The present investigation develops a thermomechanical model that combines both microscopic and macroscopic thermal resistances for non-flat, roughened, surfaces with non-metallic coatings. The thermomechanical model developed as a result of this study predicts the thermal contact resistance of several non-metallic coatings deposited on metallic aluminum substrates quite well.

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