Investigation Of Heat Transport On The Solid-solid Contact Interface At Low Temperature

At low temperature, the heat transfer between two contact bulks determinates the reliability and life of apparatus, at same time, in aerospace, cryogenics, cooling superconductor fields, the heat trasfer between two contact bulks determinates whether the thermal manager of system. The heat transfer between two contact bulks is investigated using experimental and thoerical method, which can resolve the technique key and problem of discipline. So it is a hot to disclosure the mechanism of heat transfer between two contact bulks. The main task of this paper is investigated the heat transfe between two contact bulks using experimental and thoerical method at low temperatue.With the development of the high temperature superconducting material and mini-cooler, the cooler cooling is a cooling for the cooling superconductor. The cooler cooling of superconductor, since the contact heat transfer exists between the superconductor, between superconductor and metal, it affects the temperature distribution of superconducting maganet and system, so the key factors which affects themal stability and temperature of the superconducting maganet is the contact interface resistance. The cryocooler conduction cooling system of the superconducting magnet is set up, the test is conducted in this system using static maganet and quasi-steady state, and the feature of cooling on the 35KJ model superconducting magnet is obtained. The study shown that decreasing and controlling the thermal contact resistance is the technology key. The thermal contact conduction on the cryocooler conduction cooling is the start of this study, and the investigation is conducted under supporting the National nature science Foundation(51076013), the National 863 Foundation Research(2002AA306331-4), and the Specialized Research Fund of the Doctoral Program of Higher Education(20040487039).From the Micro-Nano cryogenic view, there is a micrometer (nanometer) interface layer between two bulks contact interface, the microstructure of the interface layer is different from that of bulk material. The cryogenic interface layer may result in the thermal contact resistance, so it has an important significance and application value for studying the character of interface layer, interface layer thermal contact resistance and the heat transport of the interface layer. A temperature extrapolation is usually used at steady state method for studying the thermal contact resistance. Since the influence of microstructure of the interface layer on the thermal contact resistance is neglected using the temperature extrapolation, so it may be shortage for studying the contact interface resistance. The modulation laser photothermal is exploitively used for studying the thermal contact resistance. Using cooler as cold source, the photothemal experimental platform has been set up.The thermal physic property is basic for studying the contact resistance, since the difference of component results in the large difference of the thermal physic property. To consider the difference, ensure the reliabilty of the investigation on thermal contact resistance, first, the thermal diffusivity on the copper, stainless steel and aluminium is studied at photothermal experimental platform. The results are resported on the photothemal at a temperature range from 20 to 300K. It is consistence with the result obtained using the steady state. Based on the thermal diffusivity, the contact interface resistance is intimately investigated, at a contact pressure range from 1.2MPa to 4.28 MPa, at a temperature range from 20K to 300K, the contact interface resistance decreases with rising of the contact pressure and temperature. The new technique and theory is applied in this study, it exploit a new path to invetigation of the contact interface resistance at low temperature.The microstructure explain on cryo-interface layer is basic to resolve the contact heat transfer, the conception of three dimension cryo-interface layer is fully explain, the interface layer is clearly divided into two parts—the interface and the sub-surface. The DBITR model is set up using the ballistic and diffusive transport of the phonon. The phonon transfer coefficient is obtained using the attenuation similar between the phonon wave and electron maganet wave. The prediction of the DBITR and experiment is basiclly identical.The transfer coefficient of the phonon is affected by the interface conditon, state density of phonon, temperature. Since the transfer coefficient is complex, the full investigation on the transfer coefficient is seldom reported. The transfer coefficient of the AMM and DMM model is concluded under considering the interface condition, from the view of energy and momentum of the heat carrier, under the elastic specular scattering and diffusivity scattering. The application example about the transport coefficient between YBCO and MgO is given, the difference between the prediction and experiment is that the influence of the microstrcuture of the sub-surface layer on the phonon transport. The transfer coefficient in the AMM is obtained from the DBITR under phonon normal incidence.The comparison is conducted between the AMM and DBITR model, the result shown that the prediction of the DBITR is consistent with the experiment under the pressure contact interface, however, the difference is exist on film on matrix contact interface. It is value that the DBITR model is set up for studying the problem of the contact heat conduction.