Accurate measurement of the longitudinal thermal conductivity and volumetric heat capacity of single carbon fibers with the 3 omega method

摘要

An experimental setup for 3 omega method with a constant current source and two differential amplifiers was built to measure the thermal conductivity and the volumetric heat capacity of single polyacrylonitrile (PAN)-based carbon fiber. In complement to a well-known analytical thermal model, a numerical one was developed that can check the validity of the analytical one and can also take into account the effect of convective heat loss on the measurements. A detailed sensitivity analysis of the unknown parameters was presented that would finally help in the better design of the setup for 3 omega method. The tests were performed under vacuum and atmospheric pressure for chromel wire as a reference sample and under vacuum for two types of PAN-based carbon fiber. Detailed measurements were performed displaying the influence of convective loss and the thermal contact resistance between fiber and copper electrodes on the estimation of thermal properties of carbon fiber.