Dataset Information

Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions.

ABSTRACT: Accuracy of the Harman measurement largely depends on the heat transfer between the sample and its surroundings, so-called parasitic thermal effects (PTEs). Similar to the material evaluations, measuring thermoelectric modules (TEMs) is also affected by the PTEs especially when measuring under atmospheric condition. Here, we study the correction methods for the Harman measurements with systematically varied samples (both bulk materials and TEMs) at various conditions. Among several PTEs, the heat transfer via electric wires is critical. Thus, we estimate the thermal conductance of the electric wires, and correct the measured properties for a certain sample shape and measuring temperature. The PTEs are responsible for the underestimation of the TEM properties especially under atmospheric conditions (10-35%). This study will be useful to accurately characterize the thermoelectric properties of materials and modules.

SUBMITTER: Roh IJ

PROVIDER: S-EPMC5155428 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions.

Roh Im-Jun IJ Lee Yun Goo YG Kang Min-Su MS Lee Jae-Uk JU Baek Seung-Hyub SH Kim Seong Keun SK Ju Byeong-Kwon BK Hyun Dow-Bin DB Kim Jin-Sang JS Kwon Beomjin B

Scientific reports 20161214

Accuracy of the Harman measurement largely depends on the heat transfer between the sample and its surroundings, so-called parasitic thermal effects (PTEs). Similar to the material evaluations, measuring thermoelectric modules (TEMs) is also affected by the PTEs especially when measuring under atmospheric condition. Here, we study the correction methods for the Harman measurements with systematically varied samples (both bulk materials and TEMs) at various conditions. Among several PTEs, the hea ...[more]

PMID: 27966622

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Project description:Thermal conductivity measurements using Scanning Thermal Microscopy (SThM) usually involve heat transfer across the mechanical contact and liquid meniscus between the thermal probe and the sample. However, variations in contact conditions due to capillary effects at probe-sample contact and probe and sample wear due to mechanical contact interfere with accurate determination of the thermal conductivity. This paper presents measurements of thin film thermal conductivity using a SThM method employing a Wollaston probe in non-contact mode in synergy with detailed heat transfer analysis. In this technique, the thermal probe is scanned above the sample at a distance comparable with the mean free path of the ambient gas molecules. A Three-Dimensional Finite Element Model (3DFEM) that includes the specifics of the heat transfer between the sample and the probe in transition heat conduction regime was developed to predict the SThM probe thermal resistance and fit the thermal conductivity of the measured thin films. Proof-of-concept experimental in-plane thermal conductivity results for 240 nm and 46.6 nm Au films deposited on glass and silicon substrates were validated by experimental measurements of their electrical conductivity coupled with the Wiedemann-Franz law, with a discrepancy < 6.4%. Moreover, predictions based on a kinetic theory model for thin-film thermal conductivity agreed with the experimental results for the Au films with <6.6% discrepancy. To reduce the time and complexity of data analysis and facilitate experimental planning, an analytical model was also developed for the thermal transport between the Wollaston probe, ambient, and film-on-substrate samples. The accuracy of thin film thermal conductivity measurements using the analytical model was investigated using 3DFEM simulations. Fitted functions were developed for fast data analysis of thermal conductivity of thin films in the range of ∼100-600 W m-1 K-1 and thickness between ∼50-300 nm deposited on the two types of substrates investigated in this work, which yielded results with a discrepancy of 6-16.7% when compared to the Au films' thermal conductivity values.

Dataset Information

Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions.

Publications

Harman Measurements for Thermoelectric Materials and Modules under Non-Adiabatic Conditions.

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