Research On Thermal Conductivity Measurement With Transient Hot Wire Method

The thermal conductivity is the basic thermal properties of the material.In terms of production,life and scientific activities,thermal conductivity has a wide range of applications.Transient hot wire method,as one of the most accurate methods of measuring the thermal conductivity,plays an important role in the measurement of thermal conductivity.Based on the principle of transient hot wire method,a thermal conductivity test system based on LabVIEW was studied.For the initial resistance of the hot wire,the principle of extrapolation of the initial resistance of single hot wire was analyzed theoretically.The initial resistance of the hot wire was measured using a small current method and an extrapolation method respectively.The deviation of the result of using extrapolation and small current method to obtain initial resistance was within 0.012%.But the extrapolation method was more stable.The measurement method of initial resistance of work hot wire based on test system was studied.The steady-state resistance of the working hot wire was obtained by measuring the steady-state voltage of each measuring point under different power supply voltage,and the extrapolation of the voltage square(power)was established to measure resistance method.In order to simplify the measurement process,an improved double hot wire of initial resistance measurement method was proposed,which eliminated the influence of other resistance factors by making the difference between the measured long hot wire and the short hot wire voltage data.The deviation of the two methods to measure initial resistance was less than 0.3%.In this paper,the finite volume method was used to simulate the thermal conductivity of the transient hot wire method,and the data processing program was written by fotran language.In order to realize the integration of data acquisition system and data processing program,the method of mixed programming between LabVIEW and Fortran language was studied.According to the mixed programming theory,the dynamic link library was developed by using the data processing program,and the system integration was realized.Reliability of the test system was verified eventually.