A high sensitivity thermoelectric sensor to measure all relevant thermal transport properties has been developed. This so-called transient hot bridge (THB) decidedly improves the state of the art for transient measurements of the thermal conductivity, thermal diffusivity, and volumetric specific heat. The new sensor is realized as a printed circuit foil of nickel between two polyimide sheets. Its layout consists of four identical strips arranged in parallel and connected for an equal-ratio Wheatstone bridge. At uniform temperature, the bridge is inherently balanced, i.e., no nulling is required prior to a run. An electric current makes the unequally spaced strips establish an inhomogeneous temperature profile that turns the bridge into an unbalanced condition. From then on, the THB produces an offset-free output signal of high sensitivity as a measure of the properties mentioned of the surrounding specimen. The signal is virtually free of thermal emf’s because no external bridge resistors are needed. Each single strip is meander-shaped to give it a higher resistivity and, additionally, segmented into a long and short part to compensate for the end effect. The THB closely meets the specific requirements of industry and research institutes for an easy to handle and accurate low cost sensor. As the key component of an instrument, it allows rapid thermal-conductivity measurements on solid and fluid specimens from 0.02 to 100 W· m−1·K−1 at temperatures up to 250°C. Measurements on some reference materials and thermal insulations are presented. These verify the preliminary estimated uncertainty of 2% in thermal conductivity.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Gustafsson S.E., Karawacki E., and Khan M.N. (1979). J Phys D 12:1411
U. Hammerschmidt, V. Meier, and R. Model, “New Transient Hot Bridge Sensor to Measure the Thermal Conductivity,“ in Proc. 28th Int. Thermal Cond. Conf., St.Andrews-by-the-Sea, New Brunswick, Canada, 2005 (to be published).
Gustafsson S.E., Ahmed K., Hamdani A.J., and Maqsood A. (1982). J. Appl. Phys. 53:6064
U. Hammerschmidt, in Proc. 24th Int. Thermal Cond. Conf., P. S. Gaal, ed. (Technomic, Lancaster, Pennsylvania,1999), pp. 123–134.
Hammerschmidt U. and Sabuga W. (2000). Int. J. Thermophys. 21:217
Hammerschmidt U. (2003). Int. J. Thermophys. 24:1291
Groß U., Song Y.W., and Hahne E. (1992). Fluid Phase Equilib. 76:273
Rudtsch S. and Hammerschmidt U. (2004). Int. J. Thermophys. 25:1475
S. Rudtsch, R. Stosch, and U. Hammerschmidt, in Proc. 16th European Conference on Thermophysical Properties (ECTP 2002), London (2002).
Guide to the Expression of Uncertainty in Measurement (ISO, Geneva, 1992).
R. Model, R. Stosch, and U. Hammerschmidt, “Improved Transient Hot Strip Sensor Design by Means of FEM Simulations,” in Proc. 28th Int. Thermal Cond. Conf., St. Andrews-by-the-Sea, New Brunswick, Canada, 2005 (to be published).
U. Hammerschmidt, V. Meier, and R. Model, “JANUS: High Temperature Transient Hot Bridge Sensor,” in Proc. 28th Int. Thermal Cond. Conf., St. Andrews-by-the-Sea, New Brunswick, Canada, 2005 (to be published).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hammerschmidt, U., Meier, V. New Transient Hot-Bridge Sensor to Measure Thermal Conductivity, Thermal Diffusivity, and Volumetric Specific Heat. Int J Thermophys 27, 840–865 (2006). https://doi.org/10.1007/s10765-006-0061-2
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10765-006-0061-2