Stethoscope-type 3ω independent detector for fast measurement of material thermal conductivity.

As one of the most basic properties of materials, thermal conductivity is a key parameter to investigate the analysis and design of the particular thermal process, such as the analysis of the thermal/cool energy storage and release process, the thermal/cool energy storage system design, and so on. Also, it is the foundation of energy technology development. In order to overcome the problem that the measurement frequency of a polyimide substrate independent detector is lower and the measurement time is longer, based on the relationship among 3ω detection frequency, thermal wave penetration depth, and thermal properties of the substrate material, this paper developed a stethoscope-type 3ω independent detector based on a sapphire substrate for fast measurement of material thermal conductivity. Nickel, with a high resistance temperature coefficient, was used as the metal detector. The influence of the width of the nickel metal detector and the thickness of the sapphire substrate on the measurement accuracy was analyzed by introducing an effective heat flow ratio. The sapphire substrate independent detector was calibrated by using copper, aluminum, 304 stainless steel, quartz glass, ethylene glycol, and plexiglass with known thermal conductivities. The experiment shows that the measurement frequency of the stethoscope detector can be ten times higher than that of a Kapton film independent detector. Its measurement time is only one tenth of that of the Kapton film independent detector.