Verification of thermal conductivity measurements using guarded hot plate and heat flow meter methods

The guarded hot plate (GHP) and the heat flow meter (HFM) methods are two widely used techniques to measure the thermal conductivity (lambda) of insulation specimens. In this study, the lambda measurement of the two methods was validated using the certified reference material (CRM) IRMM-440 and an expanded polystyrene (EPS) board at temperatures from - 10 to 50 degrees C. The GHP apparatus was a commercially available apparatus for 300 mm x 300 mm specimens, and the HFM apparatus for 900 mm x 900 mm specimens was built in-house. The lambda of the CRM measured using the GHP was within 2% of the certified lambda value. Subsequently, the lambda values of specimens of nominally identical EPS with 20 mm thicknesses were measured using both the GHP and the HFM methods. A comparison of the lambda measurements showed that the two methods were consistent to within 3%. Finally, the lambda values of EPS specimens of various thicknesses from 50 to 200 mm were measured using the HFM method. Although the specimens were nominally identical, values of lambda for the specimens with thicknesses of 20-150 mm were increased by 0.09% mm(-1) at - 10 degrees C and by 0.07% mm(-1) at 10 degrees C.

Automated summary

The study validated the effectiveness of the guarded hot plate and heat flow meter methods in measuring the thermal conductivity of insulation materials, and compared the measurements of identical materials, showing a high level of consistency between the two methods in the experiments.