Methods Requiring Calibration
The calibration of comparative thermal conductivity testing methods is a critical preparation step before measurement of unknown materials. Whether calibration is performed by the user or the factory, the same basic limitations and sources of error apply.
There are two basic types of comparative thermal conductivity testing methods:
Multi-point or Secondary Calibration
This complex calibration procedure uses three or more materials to calibrate the method for a definitive range of thermal conductivity or thermal effusivity. Calibration materials should be of similar density and surface qualities to that of the sample. All testing parameters of selected reference materials, test time, power, contact agent and applied force are locked in and require re-calibration to be adjusted. Sources of greatest errors are caused by the lack of certified reference materials. Any errors introduced into the calibration procedure with use of non-certified reference materials become part of the composite accuracy of the method. Common thermal conductivity testing methods which require multi-point calibration:
- Modified Transient Plane Source (MTPS). Method is typically factory (yearly) calibrated for a definitive thermal conductivity range (ie. polymers, metals, etc) . Multiple calibration materials are not used in a traditional off-set manner, but a secondary calibration manner. The slope of the unknown sample is compared to a secondary calibration graph generated by measurement of reference materials. Demonstration materials may be used to verify operation.
- Transient Line Source (TLS). Method can be single-point or multi-point factory calibrated depending on thermal conductivity range. Demonstration materials may be used to verify operation.
Single-point calibration
This simple offset calibration is used to adjust small offsets which are typical for calibration of convection, contact and radiation effects. Typically, measurement ranges are quite small. Sources of errors include use of non-certified calibration materials, testing samples of different thickness and density to that of the calibration material. Common thermal conductivity testing methods which require single-point calibration:
- Transient Hot Wire (THW). Simple user calibration procedure on a liquid or solid of similar density to that of the sample.
- Transient Hot Strip (THS). Simple user calibration procedure on a solid reference material of similar density to that of the sample.
- Heat Flow Meter (HFM). User calibration procedure at a specific mean / delta temperature on a solid reference material of similar density to that of the sample.
- Guarded Heat Flow Meter (GHFM). User calibration procedure at a specific mean / delta temperature on a solid reference material of similar density to that of the sample.
- Guarded Comparative Longitudinal Heat Flow (GCLHF). User calibration procedure at a specific mean / delta temperature on a solid reference material of similar density to that of the sample.
References:
1 – Modified Transient Plane Source (MTPS):
Paper: M. Emanuel. 2006. Effusivity Sensor Package (ESP) System for Process Monitoring and Control. THERMAL CONDUCTIVITY 28: 256
Available at: https://memanuel.files.wordpress.com/2010/08/mathis_effusivity_sensor_technology3.pdf
ASTM:ASTM D7984-16, Standard Test Method for Measurement of Thermal Effusivity of Fabrics Using a Modified Transient Plane Source (MTPS) Instrument, ASTM International, West Conshohocken, PA, 2016, www.astm.org
2 – Transient Line Source (TLS):
Paper: B. Pilkington, P. de Wilde, S. Goodhew, and R. Griffiths. 2006. Development of a Probe for Measuring In-situ the Thermal Properties of Building Materials. The 23rd Conference on Passive and Low Energy Architecture, Geneva, Switzerland, 6-8 September 2006.
Available at: http://www.unige.ch/cuepe/html/plea2006/Vol2/PLEA2006_PAPER185.pdf
ASTM: ASTM D5334-22, Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure, ASTM International, West Conshohocken, PA, 2014, www.astm.org
1 – Transient Hot Wire (THW):
Paper: L. Loiselle, I. Fofana, and D. Hume. 2011. Influence of Transformer Oil Decay Products on its Thermal Conductivity. THERMAL CONDUCTIVITY 31, THERMAL EXPANSION 19.
Available at: https://books.google.ca/books?id=7tMSqG0HKyoC&pg=PA249&lpg=PA249&dq=Influence+of…
ASTM: ASTM D7896-14, Standard Test Method for Thermal Conductivity, Thermal Diffusivity and Volumetric Heat Capacity of Engine Coolants and Related Fluids by Transient Hot Wire Liquid Thermal Conductivity Method, ASTM International, West Conshohocken, PA, 2014, www.astm.org
2 – Transient Hot Strip (THS):
Paper: S. E. Gustafsson, E. Karawacki, and M. Nazim Khan. 1979. Transient hot-strip method for simultaneously measuring thermal conductivity and thermal diffusivity of solids and fluids. Journal of Physics D: Applied Physics, 12(9): 1411.
Available at: http://iopscience.iop.org/article/10.1088/0022-3727/12/9/003/pdf
M. Gustavsson, H. Wang, R. M. Trejo, E. Lara-Curzio, R. B. Dinwiddie, and S. E. Gustafsson. 2006. On the Use of the Transient Hot-Strip Method for Measuring the Thermal Conductivity of High-Conducting Thin Bars. International Journal of Thermophysics, 27(6): 1816-1825.
Available at: http://thermophysics.ru/pdf_doc/AutoPlay/Docs/CollectionOfManuscripts/ECTP2005paper45.pdf
3 – Heat Flow Meter (HFM):
Paper: M. Bomberg, and K. R. Solvason. Discussion of Heat Flow Meter Apparatus and Transfer Standards Used for Error Analysis. Guarded Hot Plate and Heat Flow Meter Methodology. ASTM STP 879. Eds. American Society for Testing and Materials, Philadelphia, 140-153.
Available at: https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP32904S.htm
R. P. Tye, K. G. Coumou, A. O. Desjarlais, and D. M. Haines. Historical Development of Heat Flow Meter Apparatus for Measurements of Thermal Resistance of Insulations. Thermal Insulation: Materials and Systems ASTM STP 922. American Society for Testing and Materials, Philadelphia, 651-664.
Available at: https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP18510S.htm
ASTM: ASTM C518-15, Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, ASTM International, West Conshohocken, PA, 2015, www.astm.org
4 – Guarded Heat Flow Meter (GHFM):
Paper: S. Yoon, D. E. Macphee, and M. S. Imbabi. 2014. Estimation of the thermal properties of hardened cement paste on the basis of guarded heat flow meter measurements. Thermochimica Acta, 588: 1-10.
Available at: http://www.sciencedirect.com/science/article/pii/S0040603114001695
A. Lorenzati, S. Fantucci, A. Capozzoli and M. Perino. 2016. Experimental and numerical investigation of thermal bridging effects of jointed Vacuum Insulation Panels. Energy and Buildings, 111: 164-175.
Available at: http://www.sciencedirect.com/science/article/pii/S0378778815303911
ASTM: ASTM E1530-11, Standard Test Method for Evaluating the Resistance to Thermal Transmission of Materials by the Guarded Heat Flow Meter Technique, ASTM International, West Conshohocken, PA, 2011,www.astm.org
5 – Guarded Comparative Longitudinal Heat Flow (GCLHF):
Paper: K. J. Gross, and B. Hardy. 2014. Recommended Best Practices for Characterizing Engineering Properties of Hydrogen Storage Materials.
Available at: https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/best_practices_hydrogen_storage.pdf
V. Mirkovich. 1965. Comparative Method and Choice of Standards for Thermal Conductivity Determinations. Journal of American Ceramic Society, 48(8): 387-391.
Available at: https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/best_practices_hydrogen_storage.pdf
ASTM: ASTM E1225-04, Standard Test Method for Thermal Conductivity of Solids by Means of the Guarded-Comparative-Longitudinal Heat Flow Technique, ASTM International, West Conshohocken, PA, 2004, www.astm.org