| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 100 === A thermal conductivity meter that we have used commonly requires a long time to allow system temperature to reach steady state. With the Fourier Heat Conduction Equation, we evaluate thermal conductivity by using the temperature gradient that we measured from the known measurement points of spacing. Therefore, it takes a longer period of time to measure the amount of the thermal conductivity which generally requires 10 minutes to couples of hours. By this, there is a correspondent relationship between the thermal conductivity of steady-state measurement method and the thickness of test specimens. For the lower thermal conductivity material, this solution is suitable for a thinner test specimen. It usually causes serious concerns of heat loss when a thicker test specimen spends too much time waiting for the system to reach the steady state. As for the higher thermal conductivity material, this method is better merely used on a thicker test specimen. In contrary, it would tend to have larger error in the value of thermal conductivity because the difference of temperature measurement points we gathered from a thinner specimen was small.
In this essay, we study the characteristic foundation of transient heat conduction based on a self-made raw model composed with flat double-spiral heat source measurement which qualify both heating and temperature sensing functions. We make the components tightly clipped in between the test specimens which we use for testing later. After that, we evaluate the thermal conductivity and thermal diffusivity of the test specimens by measuring the temperature of the transient plane heat source which is reactivating with the passing of time.
This measuring techniques of Transient Plane Source is concentrated on the changes between the heat source when heating and its own temperature changing over time. It takes less period of time than traditional steady-state measurement techniques and we don''t have to wait for a system to keep heat stable. In addition, I examine the measurement difference of the measuring techniques of Transient Plane Source in the atmospheric and vacuum environment. My finding in this research discovers that the vacuum environment can efficiently isolate from the impact to the test specimens which is potentially influenced by external environment convection. With this discovery, we can significantly increase the measurement accuracy.
This Transient Plane Source Measurement System I have worked on has been helping me to obtain the following data. My research measured from the Brass JIS C1100 within 5.75 seconds appeared that the value of thermal conductivity was 370.6 W/m‧k and the normal average difference was less than 5%. As for the Aluminum Nitride, AIN, it took me 3.5 seconds to gather the value of thermal conductivity at 188.5 W/m‧k which was less 0.78% different from the statistics recorded at the Chung-shan Institute of Science and Technology in Taiwan. The value of thermal conductivity I collected when tested on Silicon Wafer in 5 seconds was 146.2 W/m‧k and the normal average difference was less than 7.47%. Spent 4.6 seconds to work on the Brass JIS C2680, I obtained the value of thermal conductivity at 123.9 W/m‧k which was less 4.6% different from the nominal average. As for the value of thermal conductivity measured from Stainless Steel within 80 seconds, it was 20.69 W/m‧k and the normal average difference was less 3.45%. When tested on a acrylic sheet within 180 seconds, I obtained the values of thermal conductivity at 0.202 W/m‧k which was less 3.35% different from the nominal average.
In this thesis, we have successfully established a efficient measuring system of transient heat conduction coefficient by taking lower cost efficiency. In the measurement of large thermal conductivity range from 0.202 to 370.6 W/m‧k), the overall error was lower under 7.47% and the time of measurement was within 180 seconds. To the unknown material of thermal conductivity, this device provides the academic research a efficient, precise and time-saving measurement application.
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