3.3 Effective Thermal Diffusivity and Conductivity
155
Fig. 3.22 Average effective thermal conductivities of all azimuthal sets with the improved method
(a) and with the expanded uncertainty at a 95% level of confidence (b)
mal distribution with the mean and standard uncertainties obtained in Sect. (3.3.5.3).
Then, it should generate the same quantity of samples of graphite density, specific
heat capacity, and averaged porosity from their distributions. The 95% expanded
uncertainty is obtained by counting the 95% possibility interval from the 10
6 conductivities. The final distribution of conductivity is slightly asymmetric according to
the Monte Carlo method.
In Fig. (3.22), the effective thermal conductivity and uncertainty obtained in this
facility are compared with the results of HTTU in South Africa [10] and SANA
in Germany [25]. It should be noted that the results of SANA-1 and SANA-2 are
the measured points in Figs. 4-79 and 4-109, of IAEA-TECDOC-1163 [25], respectively. The satisfactory agreement in the comparison illustrates the methodology of
the inversed method, as well as the conversion method used in this experiment, is
reasonable and effective to process experimental data. The valid highest temperatures of conductivity in the other two experiments are only about 900
◦ C in SANA
and 1000
◦ C in HTTU, but the tests in this study have provided the effective thermal
diffusivity and conductivity whose temperatures are up to 1,200
◦ C. Since it does not
have an obvious drawback in the methodology and experimental limit, even with a
higher temperature, the facility can be upgraded to measure the higher temperature
effective thermal diffusivity and conductivity of pebble bed up to 1,600
◦ C by fitting
the sheathed tungsten-rhenium thermocouples furthermore.
3.3.6 Short Summary
This section first presents an overview of the four independent tests, which are conducted to measure the thermal effective diffusivity and conductivity of a pebble bed
in the full-radius-scale heat test facility. The two vacuum tests and the two helium
155
Fig. 3.22 Average effective thermal conductivities of all azimuthal sets with the improved method
(a) and with the expanded uncertainty at a 95% level of confidence (b)
mal distribution with the mean and standard uncertainties obtained in Sect. (3.3.5.3).
Then, it should generate the same quantity of samples of graphite density, specific
heat capacity, and averaged porosity from their distributions. The 95% expanded
uncertainty is obtained by counting the 95% possibility interval from the 10
6 conductivities. The final distribution of conductivity is slightly asymmetric according to
the Monte Carlo method.
In Fig. (3.22), the effective thermal conductivity and uncertainty obtained in this
facility are compared with the results of HTTU in South Africa [10] and SANA
in Germany [25]. It should be noted that the results of SANA-1 and SANA-2 are
the measured points in Figs. 4-79 and 4-109, of IAEA-TECDOC-1163 [25], respectively. The satisfactory agreement in the comparison illustrates the methodology of
the inversed method, as well as the conversion method used in this experiment, is
reasonable and effective to process experimental data. The valid highest temperatures of conductivity in the other two experiments are only about 900
◦ C in SANA
and 1000
◦ C in HTTU, but the tests in this study have provided the effective thermal
diffusivity and conductivity whose temperatures are up to 1,200
◦ C. Since it does not
have an obvious drawback in the methodology and experimental limit, even with a
higher temperature, the facility can be upgraded to measure the higher temperature
effective thermal diffusivity and conductivity of pebble bed up to 1,600
◦ C by fitting
the sheathed tungsten-rhenium thermocouples furthermore.
3.3.6 Short Summary
This section first presents an overview of the four independent tests, which are conducted to measure the thermal effective diffusivity and conductivity of a pebble bed
in the full-radius-scale heat test facility. The two vacuum tests and the two helium