2026 ASEE Annual Conference & Exposition

Wherever two solids meet, such as heat sinks on chips, bolted joints in engines, battery pack interfaces, and exchanger plates, thermal contact resistance (TCR) frequently dominates the thermal budget, as the actual surfaces only touch at minuscule asperities with trapped gaps of air or filler between them. The value of the TCR is susceptible to material combinations, oxidation, cleanliness, flatness, hardness, clamping pressure, and the presence or thickness of thermal interface materials. Handbook values or purely analytical models may be orders of magnitude incorrect for a particular assembly due to the nonlinear interactions between all these elements. Therefore, under the precise conditions a design would encounter, lab measurement is the most dependable method of obtaining a usable TCR.

This “Bring Your Own Experiment” (BYOE) paper describes a modular, lab-scale implementation of the ASTM E1530 guarded heat-flow meter (GHFM) method. The modular architecture uses swappable components so instructors can change samples, Thermal Interface Materials (TIMs), and meter bar materials and lengths, while preserving the E1530 boundary conditions and quasi-1D guarded geometry. The students can simply expand experiments by sweeping pressure and different TIM and sample selections. This setup was built for an undergraduate heat transfer laboratory course.

The experimental setup allows measurements of one-dimensional heat transfer through a specimen under steady state conditions using Fourier’s law. A silicon wafer test sample is mounted in a stack between a heat source, two meter bars, and a heat sink. Thermistors are placed at specific locations in the meter bars to measure the thermal gradient in the meters bars. A surrounding “guard” region is held at nearly the same temperature as the meter path, suppressing lateral losses so the conduction is effectively 1D. With heat flux q known, the bulk of the specimen and the interface thermal resistance follow from R=ΔT/q. To correlate the dependence of the TCR on clamping force, this setup includes an integrated load cell into the stack to measure and control the normal force at the interface. Students vary clamping pressure quantitatively, measure the TCR as a function of clamping pressure, and interpret results through both thermal and mechanical lenses (surface conformity, micro-contact area).

The experiment targets three learning outcomes: (i) translating the heat equation into experimental evidence through analysis of T(x) profiles; (ii) understanding how assembly variables govern TCR, as well as when a TIM meaningfully alters performance; and (iii) practicing experimental judgment (steady-state detection, uncertainty budgeting, replication). Because the setup construction is transparent and inexpensive, the exercise avoids “black-box” measurement and foregrounds the craft that determines credibility.
This BYOE paper is written with a goal of allowing students to examine steady-state gradients, reproduce assembly procedures, assess the significance of measurement uncertainty, and provide data that directly informs design margins and safety considerations, while also validating models in a controlled environment.