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.

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A technique adapted from the guarded-comparative-longitudinal heat flow method was selected for the measurement of the thermal conductivity of a nuclear fuel compact over a temperature range characteristic of its usage. This technique fulfills the requirement for non-destructive measurement of the composite compact. Although numerous measurement systems have been created based on the guarded-comparative method, comprehensive systematic (bias) and measurement (precision) uncertainty associated with this technique have not been fully analyzed. In addition to the geometric effect in the bias error, which has been analyzed previously, this paper studies the working condition which is another potential error source. Using finite element analysis, this study showed the effect of these two types of error sources in the thermal conductivity measurement process and the limitations in the design selection of various parameters by considering their effect on the precision error. The results and conclusions provide valuable reference for designing and operating an experimental measurement system using this technique.

The present numerical study examines the influence of horizontal louvres (Venetian blinds) on the convective heat transfer from a vertical isothermal surface. A steady, laminar, two dimensional, conjugate conduction/convection solution to this problem has been obtained using the finite element method. Detailed comparisons are made with temperature field and local Nusselt number data obtained using a Mach-Zehnder Interferometer. Also, numerically predicted stream function contours are compared to streamlines obtained from flow visualization experiments. All results are obtained for Pr = 0.7, as the intended application of this study is for air. Results show that as the blind tip-to-plate spacing decreases, the difference between numerical solutions and experimental results increase. This suggests that radiation heat transfer may be a significant factor at smaller blind spacings.