Date of Graduation

5-2025

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Hu, Han

Committee Member

Leylek, Jim

Abstract

In this paper, we have investigated the effect of thermal interface materials (TIMs) on the accuracy and uncertainty of thermal conductivity measurements. A modified ASTM D5470 thermal resistance tester (TRT) is developed to measure the out-of-plane thermal conductivity of pyrolytic graphite (PG) and grade 2 titanium (TiG2) with and without TIMs. Compared to the ASTM D5470 standard, this modified design uses three thermocouples per side to support regressive analysis and explores the use of TIMs.s Nine PG samples and four TiG2 samples of varying thickness have been tested to obtain thermal resistance as a function of sample thickness. The steady-state temperature profiles were used for heat flux and thermal resistance calculation. The results reveal that TIMs significantly reduce measurement uncertainty for both samples, i.e., 42.85% for TiG2 and 48.81% for PG. The effect of TIMs on the measurement accuracy diverges, with a far more pronounced effect on TiG2 than PG. This is owing to the higher out-of-plane thermal conductivity of TiG2 (~ 17 W/mK) than PG (~ 2 W/mK). For materials with higher thermal conductivity, the percentage of the contact resistance between the sample and sample holder in the total resistance is very high. Thus, good control of the contact resistance by using TIMs is helpful in improving the measurement accuracy. For lower conductivity materials, the weight of contact resistance is lower and the effect of TIMs is thus less pronounced.

Keywords

Thermal Conductivity Measurement; Pyrolytic Graphite; Titanium; Heat Transfer; Thermal Contact Resistance; Thermal Interface Materials

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