Uncertainty Analysis Of Thermal Bridge Method And Comparative Study Of Thermal Bridge Method And Self-heating Method

With the development of experimental measurement methods and measuring instruments,many experimental methods have emerged for the measurement of thermal conductivity of one-dimensional nanostructures.The thermal bridge method and the self-heating method are both widely used measurement methods.In-depth study of these two measurement methods is of great significance for understanding micro-nano scale heat transfer.The measuring principles of thermal bridge method and self-heating method are deduced.The self-heating method measurement device for measuring the thermal conductivity of one-dimensional nanomaterials is designed and manufactured,the self-heating method measurement platform is introduced.The copper-nickel alloy nanowires produced by the liquid-phase reduction method are determined as the test samples for the comparative measurement.Uncertainty analysis is performed on the thermal bridge measurements of a carbon nanotube sample and a cadmium selenide nanowire sample.Both the Taylor series method and the Monte Carlo method are used to figure out the propagation of the errors in the direct measurements.Our results show that the uncertainty of the thermal conductance decreases as the thermal conductance of the measured sample decreases,which can be attributed to the increase in the temperature drop on the measured sample.This finding indicates that increasing the measured length of the sample or increasing the Joule heating generated on the heat source can reduce the measurement uncertainty.And the influence of the uncertainty of a single direct measurement is analyzed.Using the lock-in amplifier to measure the AC voltage drop of the variable resistance in the thermal bridge method can improve the measurement accuracy of the thermal bridge method.The thermal bridge measurement system and the self-heating measurement system were used to measure the thermal conductivity of a single copper-nickel alloy nanowire,and a comparative study was made between the two results.The comparison results show that the thermal bridge method and the self-heating method have basically the same trend in the results of measuring the thermal conductivity,and the thermal conductivity of the copper-nickel alloy nanowires increases with the increase in temperature.The difference between the test results of the two methods is less than 15%.The measurement results of thermal bridge method and self-heating method show that copper-nickel alloy nanowires not only have high thermal conductivity,but also have excellent electrical conductivity.The Lorentz number of copper-nickel alloy nanowire is less than 2.45×10^-8 W·?/K²,and it decreases as the temperature decreases.