Experiment Research On Solid Interface Thermal Contact Conductance Coefficient

Due to the exist of microcosmic roughness in the contact surfaces, when two solid interfaces contact each other, the real contact area is only a small fraction of the nominal contact area, and they only contact in some discrete microscopic asperities. This imperfect contact between the interfaces causes the constriction of the heat flow and the sudden change of the temperature between the solid interfaces. This phenomenon is called thermal contact conductance (TCC), and it is widely used and developed in the fields of aerospace, metallurgy, chemical engineering, nuclear energy, mechanical manufacture, microelectronics etc.. Since the researches on TCC between two solid interfaces have become more and more importance in various fields, it is necessary to carry out further research on its producing mechanism and the main influencing factors.After reviewing relative literatures at home and abroad, the present research analyzes the main factors influencing TCC. The main factors influencing the heat transfer between two solid interfaces includes the micro-geometry of contacting surfaces, such as surface roughness, surface waviness, surface's rake; The situation of intefacial pressure, such as contact pressure and the load history; The condition of temperature, such as interfcial temperature, the heat flow's density and direction, the changing history of the temperature; the material's property, such as the thermophysics properties of the contact material and the medium; The condition of contact interfaces, such as whether it have other medium or relative slide between the interfaces. Considering all the above factors, the research on TCC between the solid interfaces is truly a complex one.The measurement of the TCC coefficient is emphasized in the present research. Taking the main influencing factors on TCC into consideration, a set of self-developed TCC experimental system was employed and related data collecting and computing software system was also developed. The materials and dies which are widely used in material processing, such as aluminum alloy and 5CrMnMo die steel, stainless steel and stainless steel, pure copper and 3Cr2V8W alloy steel, GH4169 and 5CrMnMo die steel, TC11 and 5CrMnMo die steel, TA15 and 5CrMnMo die steel are used as subjects in the experiments. The TCC between each pair is analyzed under different contact pressure, different interfacial temperature, different contact condition, and in different contact process. The relationships between TCC and interfacial temperature, contact pressure, medium, contact process are analyzed respectively, and the conclusions are as follows:1. The TCC coefficient is not direct proportion to interfacial temperature.2. The TCC coefficient is roughly in proportion to contact pressure.3. The medium between the interfaces can effectively change the TCC coefficient. A sound thermal conductivity medium can increase the TCC coefficient, but a malfunctioning thermal conductivity medium can reduce the TCC coefficient.4. In the same contact condition, the TCC coefficient will be different when the contact process is different.