Extending Transient Plane Source-Based Measurements for Accurate Determination of Thermal Properties
Doctoral thesis, 2025
The Transient Plane Source (TPS) method is a widely used technique for measuring the thermal properties of isotropic materials, including the thermal conductivity, the thermal diffusivity, and the specific heat capacity. To accommodate various sample geometries and samples with directional properties, several variants of the TPS method have been developed.
One variant was designed to characterize micrometre-thick layers with a low thermal conductivity ( < 2 W/(m·K)), which involves sandwiching the layer between the TPS probe and backing substrates. By assuming one-dimensional (1D) heat flux across the layer after a certain period, its thermal conductivity can be estimated by incorporating Fourier’s law in the calculation. However, thermal contact resistance impedes heat conduction and leads to significant errors. This thesis shows that introducing a liquid interface material, e.g., deionized water, effectively reduces and enables arcuate thermal conductivity determination (errors < 4 %) from measurements of layers with different thicknesses.
Once the layer has either a higher thermal conductivity ( > 2 W/(m·K)) or a greater thickness ( > 600 μm), the measured thermal conductivity tends to be significantly overestimated, as the heat flux across the layer can no longer be assumed to be 1D. To overcome this limitation, the Layer 2D model, which accounts for 2D heat flux within the layer, was proposed. This model extends the measurable range of thermal conductivity by an order of magnitude (up to 20 W/(m·K)) and thickness by about three times (up to 2000 μm), while maintaining errors below 10 %.
Another TPS variant was developed that allows to directly characterize the specific heat capacity. In this approach, the sample is placed in a holder that is attached to the TPS probe. Although the sample-holder assembly is surrounded by thermal insulation, the influence of heat loss increases over time and eventually introduces substantial errors, particularly for low thermal conductivity samples. To address this issue, a novel data analysis method assisted by finite element simulations was proposed, which allows for precise estimation of heat loss and thus accurate determination of the heat capacity (error < 4 %).
Overall, this study offers critical insights that significantly extend the applicability of TPS measurements, thereby contributing to the advancement of thermal property characterization.
One variant was designed to characterize micrometre-thick layers with a low thermal conductivity ( < 2 W/(m·K)), which involves sandwiching the layer between the TPS probe and backing substrates. By assuming one-dimensional (1D) heat flux across the layer after a certain period, its thermal conductivity can be estimated by incorporating Fourier’s law in the calculation. However, thermal contact resistance impedes heat conduction and leads to significant errors. This thesis shows that introducing a liquid interface material, e.g., deionized water, effectively reduces and enables arcuate thermal conductivity determination (errors < 4 %) from measurements of layers with different thicknesses.
Once the layer has either a higher thermal conductivity ( > 2 W/(m·K)) or a greater thickness ( > 600 μm), the measured thermal conductivity tends to be significantly overestimated, as the heat flux across the layer can no longer be assumed to be 1D. To overcome this limitation, the Layer 2D model, which accounts for 2D heat flux within the layer, was proposed. This model extends the measurable range of thermal conductivity by an order of magnitude (up to 20 W/(m·K)) and thickness by about three times (up to 2000 μm), while maintaining errors below 10 %.
Another TPS variant was developed that allows to directly characterize the specific heat capacity. In this approach, the sample is placed in a holder that is attached to the TPS probe. Although the sample-holder assembly is surrounded by thermal insulation, the influence of heat loss increases over time and eventually introduces substantial errors, particularly for low thermal conductivity samples. To address this issue, a novel data analysis method assisted by finite element simulations was proposed, which allows for precise estimation of heat loss and thus accurate determination of the heat capacity (error < 4 %).
Overall, this study offers critical insights that significantly extend the applicability of TPS measurements, thereby contributing to the advancement of thermal property characterization.
thermal conductivity
finite element simulation
polymer.
Transient Plane Source method
specific heat capacity
data analysis
Lecture hall HA2, Hörsalsvägen 4
Opponent: Vlastimil Boháč, Slovak Academy of Sciences, Slovak
Author
Zijin Zeng
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Liquid Interface for Accurate Intrinsic Thermal Conductivity Measurements of Polymer Films Using the Transient Plane Source Method
Journal of Thermal Science and Engineering Applications,;Vol. 17(2025)
Journal article
Poly(benzodifurandione) Coated Silk Yarn for Thermoelectric Textiles
Advanced Science,;Vol. 11(2024)
Journal article
Extending the Transient Plane Source Scanning method for determining the specific heat capacity of low thermal conductivity materials through a numerical study
Thermochimica Acta,;Vol. 742(2024)
Journal article
Z. Zeng, J. Gustavsson, C. Müller, and B. Mihiretie, Improved Transient Plane Source Measurements of Layer–Substrate Structures via a Semi‑Analytical Temperature Response Model
P. Sowinski, Z. Zeng, et. al., Prediction of the thermal conductivity of polypropylenes and propylene copolymers based on crystallinity or elastic modulus
We need thick jackets to stay warm during the long Swedish winters. The insulation layers used in these jackets—composed of e.g. down or polyester fibers—have a very low thermal conductivity, meaning they slow down the flow of heat between our bodies and the icy air that surrounds us. The thicker the jacket, the greater the thermal barrier it creates against heat loss to the environment.
Another important property of a “thermal barrier” is its heat capacity—its ability to absorb and store heat. When you first put on a jacket, part of your body heat is not immediately transported to the environment; instead, it first warms up the jacket itself. This is why you might feel a brief chill just after putting on a jacket, before it adjusts to your body temperature.
To quantify these two key thermal properties—thermal conductivity and heat capacity—scientists have many advanced measurement techniques at their disposal. Each technique comes with advantages and disadvantages. The Transient Plane Source (TPS) method is one such technique. It enables accurate and highly reproducible measurements of thermal properties through the use of precise instrumentation. The TPS method has its challenges, especially when characterizing the thermal conductivity of micrometer-thick layers and the heat capacity of low thermal conductivity samples.
This thesis addresses these challenges by developing new models and experimental procedures that allow to extend the capabilities of the TPS technique. In doing so, it contributes to the design of better thermal management materials—whether for keeping people warm in cold winters or protecting sensitive electronics from overheating.
Another important property of a “thermal barrier” is its heat capacity—its ability to absorb and store heat. When you first put on a jacket, part of your body heat is not immediately transported to the environment; instead, it first warms up the jacket itself. This is why you might feel a brief chill just after putting on a jacket, before it adjusts to your body temperature.
To quantify these two key thermal properties—thermal conductivity and heat capacity—scientists have many advanced measurement techniques at their disposal. Each technique comes with advantages and disadvantages. The Transient Plane Source (TPS) method is one such technique. It enables accurate and highly reproducible measurements of thermal properties through the use of precise instrumentation. The TPS method has its challenges, especially when characterizing the thermal conductivity of micrometer-thick layers and the heat capacity of low thermal conductivity samples.
This thesis addresses these challenges by developing new models and experimental procedures that allow to extend the capabilities of the TPS technique. In doing so, it contributes to the design of better thermal management materials—whether for keeping people warm in cold winters or protecting sensitive electronics from overheating.
Hybrid and Organic Thermoelectric Systems (HORATES)
European Commission (EC) (EC/H2020/955837), 2021-03-01 -- 2025-02-28.
Subject Categories (SSIF 2025)
Other Engineering and Technologies
Manufacturing, Surface and Joining Technology
Ceramics and Powder Metallurgical Materials
Textile, Rubber and Polymeric Materials
Other Mechanical Engineering
Mechanical Engineering
Areas of Advance
Energy
Materials Science
Infrastructure
Chalmers Laboratory of Fluids and Thermal Sciences
Chalmers Materials Analysis Laboratory
DOI
10.63959/chalmers.dt/5784
ISBN
978-91-8103-327-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5784
Publisher
Chalmers
Lecture hall HA2, Hörsalsvägen 4
Opponent: Vlastimil Boháč, Slovak Academy of Sciences, Slovak