Thermal Contact Conductance of Nominally Flat, Rough Surfaces in a Vacuum Environment

1966 ◽  
pp. 773-794
Keyword(s):  
Rough Surfaces ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Contact Conductance

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.

Elastoplastic Contact Conductance Model for Isotropic Conforming Rough Surfaces and Comparison With Experiments

1996 ◽  
Vol 118 (1) ◽  
pp. 3-9 ◽  
Author(s):  
M. R. Sridhar ◽  
M. M. Yovanovich
Keyword(s):  
Rough Surfaces ◽  
Thermal Contact ◽  
Material Behavior ◽  
Thermal Contact Conductance ◽  
Elastic Model ◽  
Time Data ◽  
Contact Conductance ◽  
Plastic Model ◽  
Elastoplastic Contact ◽  
Wide Range

A New thermal elastoplastic contact conductance model for isotropic conforming rough surfaces is proposed. This model is based on surface and thermal models used in the Cooper, Mikic, and Yovanovich plastic model, but it differs in the deformation aspects of the thermal contact conductance model. The model incorporates the recently developed simple elastoplastic model for sphere-flat contacts, and it covers the entire range of material behavior, i.e., elastic, elastoplastic, and fully plastic deformation. Previously data were either compared with the elastic model or the plastic model assuming a type of deformation a priori. The model is used to reduce previously obtained isotropic contact conductance data, which cover a wide range of surface characteristics and material properties. For the first time data can be compared with both the elastic and plastic models on the same plot. This model explains the observed discrepancies noted by previous workers between data and the predictions of the elastic or plastic models.

Fractal Model for Thermal Contact Conductance

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
Mingqing Zou ◽  
Boming Yu ◽  
Jianchao Cai ◽  
Peng Xu
Keyword(s):  
Random Number ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Fractal Model ◽  
Thermal Contact Conductance ◽  
Bulk Resistance ◽  
Contact Conductance ◽  
Proposed Model ◽  
Fractal Parameters ◽  
Good Agreement

A random number model based on fractal geometry theory is developed to calculate the thermal contact conductance (TCC) of two rough surfaces in contact. This study is carried out by geometrical and mechanical investigations. The present study reveals that the fractal parameters D and G have important effects on TCC. The predictions by the proposed model are compared with existing experimental data, and good agreement is observed by fitting parameters D and G. The results show that the effect of the bulk resistance on TCC, which is often neglected in existing models, should not be neglected for the relatively larger G and D. The main advantage of this model is the randomization of roughness distributions on rough surfaces. The present results also show a better agreement with the practical situation than the results of other models. The proposed technique may have the potential in prediction of other phenomena such as friction, radiation, wear and lubrication on rough surfaces.

Modeling of Thermal Contact Conductance

2010 ◽  
Author(s):  
Mikhail V. Murashov ◽  
Sergey D. Panin
Keyword(s):  
Heat Transfer ◽  
Plastic Material ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Material Behavior ◽  
Thermal Contact Conductance ◽  
Nonstationary Temperature ◽  
Random Component ◽  
Contact Conductance ◽  
Elastic Plastic

Nowadays a new science direction has arisen from decades of experimental work carried out in 20th century — micromechanics of contact processes (deformation, heat transfer, electric conduction). To determine contact area a dynamic elastic-plastic deformation problem is to be solved even in the simplest case — butt contact of two rough surfaces under pressure. It is followed by the solution of spatial boundary heat transfer problem to obtain nonstationary temperature distribution for two bodies. In principal, this stage is not difficult to perform with finite element program ANSYS. Meanwhile the questions concerning deformation and conduction through oxide films of metals as well as directional effect remain. In the literature there are attempts to simulate thermal contact conductance numerically of such authors as M.K.Thompson, S.Lee et al, M. Ciavarella, M.M.Yovanovich and others. The disadvantages of existing spatial models are: - surfaces profiles has no random component; - only elastic or only plastic material behavior; - microroughness is not considered. In the present work the roughness before contact of two rough surfaces of copper bodies was presented as spatial two-level (roughness and microroughness) model with the use of fractal Weierstrass–Mandelbrot function. In quasistatic approach the 3D deformation and heat transfer problems of contacting bodies under pressure were solved within elastic-plastic material behavior. Contact ANSYS elements were used. Copper compression diagram was replaced by multilinear model of isotropic hardening. From the cycle of calculations real contact areas, shapes of contact spots, temperature and stress distributions were determined for the range of pressures. Good agreement with experimental data took place only when microroughness is considered.

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