Thermal contact conductance of composite cylinders - An experimentalstudy
When two concentric cylinders are assembled with a slight interference fit and heat flows radially through such a joint, the contact at the interface may improve or deteriorate depending on several factors, including the direction of heat flow, the magnitude of the heat flux, and the thermomechanical properties of the materials of the two cylinders. This paper deals with the design and construction of an apparatus to measure the thermal contact conductance of cylindrical joints as a function of the heat flux. Results are presented for stainless steel -> stainless steel and stainless steel -» aluminum composite cylinders, for radially outward heat flow. It is noted that the results obtained are in reasonable agreement with those predicted by theory.
A major factor determining the insulating quality of a liquid under high electrical stress will be the nature of the interfaces between the liquid and the metal electrodes. In practical situations there will often be a solid dielectric layer interposed between the liquid and one or both the electrodes and in these cases there will be liquid/solid dielectric as well as solid dielectric/metal interfaces to consider. These interfaces are very important because in many instances they are the essential barriers controlling electron flow to or from the metal electrodes. This contribution to the review of liquid insulation is concerned with their electrical nature and the way in which they might exert influence on electrical breakdown.