Experimental And Theoretical Investigation On Low-temperature Interfacial Thermal Contact Resistance

Interfacial thermal contact resistance (ITCR) has profound theoretical and practical value. Started from extensive investigation on Kapitza resistance in 1930's and later on contact resistance in 1960's, this area had continuously attracted numerous researchers, and had revealed its complexity and depth. Basing on projects like: Novel Thermal Management of Micro-Satellites and Design & Optimization of Superconductive (SMES) Cryo-systems, and Photothermal method of ITCR measurement, this thesis reports the author's efforts in both experimental and theoretical aspects of low temperature interfacial thermal resistance.From the perspective of Micro-cryogenics engineering, a micro or nano scale interfacial layer exists at the contact region, which has a property different from bulk material on either side of the interface. Proper modeling of this lay will explain ITCR, and should have great impact both experimentally and theoretically.As to theoretical work, it focuses on the identification and systematic comparison of various thermal resistance mechanisms in the interfacial layer. The present study proposes several definition of interfacial layer by emphasizing"defects"of different scale: from macroscopic discontinuity of heat flow down to micro-scale of heat carrier scattering events. Constriction resistance and boundary resistance were adopt to approximate the whole range of thermal resistance effect. A unified model was then constructed. Especially, faithful modeling of the rough surface was given priority that multi-scale nature of surface roughness was retained using fractal modeling. The effect of this intrinsic characteristic was analyzed, and some possible explanation of seemingly strange temperature dependence of ITCR at low temperature was posed.As to experimental work, Photo-thermal method was applied to cryogenic temperature, its applicability at cryogenic temperature was verified, and its merits were also discussed.It is crucial to study ITCR in a thermal system rather than itself, as ITCR is not always the bottleneck of engineering problems. To illustrate this, its importance in SMES current leads design was discussed. Besides the work's value in SMES cable design & optimization, this analysis gives a vivid illustration of the importance of knowledge in ITCR and its control.