In-plane thermal anisotropy of natural cork and its variability

[Display omitted] •First-time appraisal of thermal diffusivity of cork along its main growth directions.•In-plane thermography and thermal ellipsometry assessment of natural cork on heating.•Insights on natural cork’s thermal anisotropy and orientation-dependent variability.•Natural cork thermal con...

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Bibliographic Details
Published in:Measurement : journal of the International Measurement Confederation 2025-01, Vol.242, p.116062, Article 116062
Main Authors: Santos, T., Amaral, J.S., Amaral, V.S., Costa, V.A.F.
Format: Article
Language:English
Subjects:
Hot Disk
Infrared thermography
Natural cork
Thermal anisotropy
Thermal conductivity
Thermal diffusivity
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Summary:[Display omitted] •First-time appraisal of thermal diffusivity of cork along its main growth directions.•In-plane thermography and thermal ellipsometry assessment of natural cork on heating.•Insights on natural cork’s thermal anisotropy and orientation-dependent variability.•Natural cork thermal conductivity measurements ranging from 0.033 to 0.048 W/(m·K).•Thermal anisotropy/ellipsometry of natural cork varies within a range of 23%. This study investigates the natural cork thermal anisotropy and its variability using plane slice samples of 1.4 mm thickness, cut along the principal radial, longitudinal, and tangential directions, from bark previously treated for cork stoppers production. Heating was pointwise applied to the rear face using a copper needle coupled to a Peltier element, while an in-plane thermographic technique monitored temperature evolution on the front surfaces using a Flir SC5650 infrared camera. Thermal diffusivity measurements yielded values of 0.172 ± 0.038 mm2/s (radial), 0.161 ± 0.022 mm2/s (longitudinal), and 0.160 ± 0.027 mm2/s (tangential). Additionally, a volumetric heat capacity of 0.25 MJ/(m3·K) was determined using the Hot Disk technique. This information enabled the calculation of thermal conductivity, ranging from 0.033 to 0.048 W/(m·K). Findings align with existing literature, which reports thermal diffusivity between 0.08 and 0.24 mm2/s and thermal conductivity between 0.035 and 0.045 W/(m·K). This study contributes valuable insights into the thermal properties of natural cork and their orientation-dependent variability.
ISSN:0263-2241
DOI:10.1016/j.measurement.2024.116062