Design and Validation of a High-Temperature Comparative Thermal-Conductivity Measurement System

Abstract

A measurement system has been designed and built for the specific application of measuring the effective thermal conductivity of a composite, nuclear-fuel compact (small cylinder) over a temperature range of 100 • C to 800 • C. Because of the composite nature of the sample as well as the need to measure samples pre-and postirradiation, measurement must be performed on the whole compact non-destructively. No existing measurement system is capable of obtaining its thermal conductivity in a non-destructive manner. The designed apparatus is an adaptation of the guardedcomparative-longitudinal heat flow technique. The system uniquely demonstrates the use of a radiative heat sink to provide cooling which greatly simplifies the design and setup of such high-temperature systems. The design was aimed to measure thermalconductivity values covering the expected range of effective thermal conductivity of the composite nuclear fuel from 10 W · m −1 · K −1 to 70 W · m −1 · K −1 . Several materials having thermal conductivities covering this expected range have been measured for system validation, and results are presented. A comparison of the results has been made to data from existing literature. Additionally, an uncertainty analysis is presented finding an overall uncertainty in sample thermal conductivity to be 6 %, matching well with the results of the validation samples.

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

“…The measurements are taken at a mean temperature between the hot and cold ends of a sample and there may be difficulties due to contact resistances [27].…”

The design of high-temperature thermal conductivity measurements apparatus for thin sample size

“…The created equipment has a specification only for thin material testing and does not allow the placing of a thermocouple on the sample material, so to determine the surface temperature of the material or sample (TH and TC) only be done by calculation. Meanwhile, from other research which using the same method and allowing the thermocouple to be bored to the material sample, the thermal contact resistance does not significantly affect the calculation of TH and TC because those values were measured directly using a bored thermocouple in the sample [15]. Several methods were applied such as pressure application, liquid/gel adding, or minimize the probe for minimizing thermal contact resistance.…”

“…Other proposed thermal conductivity measurements have proposed using point probe method [10] and stamp sensor method [11,12,13] that has the capability in in-situ measurements, but this method also has a limitation in high-temperature measurements. The common method in high-temperature thermal conductivity measurements is axial heat flow based on the standard of ASTM E1225-99 [14] which use a bored thermocouple in the specimen [15,16]. Unfortunately, the last method could not measure for a thermoelectric method which usually thins form and fragile in the machining process.…”

Investigation of thermal transport in composites and ion beam irradiated materials for nuclear energy applications

“…For hightemperature measurements, large radiative losses through the surface and unavailability of high-temperature thermocouples make direct measurement impractical. 10 Xenon thermal flash and more recently laser flash method have become the primary methods used for measurement of thermal transport in materials utilized for nuclear applications. 5,11,12 It is applied on a disk shaped specimen with flat parallel surfaces.…”