Abstract:
Compressible materials are popularly applied in thermal insulation applications. Measuring the
thermal conductivity of those materials is a challenge. Existing measuring methods are mostly
focused on measuring the thermal conductivity of rigid materials. It causes in-accuracies due to
several reasons such as externally applied pressure, change of dimensions of the specimen, and
change of density of the specimen while being tested in the case of compressible materials.
Therefore, in this research work, a dedicated concept of measuring the thermal conductivity of
compressible materials was developed and fabricated a device complying with the industry
standards. According to the literature review which was conducted initially, several thermal
conductivity measuring devices which can be possibly used for compressible materials were
identified. Based on the literature review, several conceptual designs were finalized. A heat
flow meter apparatus that is currently available at the author’s affiliation was then studied and
tested to identify the inaccuracies and difficulties of the heat flow meter method when utilizing
incompressible materials. From all the conceptual designs developed, a concept similar to the
hot wire method was identified and developed as a steady-state method. A mathematical model
for the finalized concept was then developed based on the theories of heat transfer. A computer
simulation was also done by using ANSYS simulation software to identify the design
parameters of the device. Finally, the device was fabricated and tested for accuracy using a coirbased
composite. Thermal conductivity tested with the currently available heat flow meter of
compressible coir-based composite material was less than 0.5 𝑊/𝑚𝐾. For the same material,
the method developed by this project gave an acceptable thermal conductivity value which is
0.211 𝑊/𝑚𝐾.
