Chapter 3
Experiments in Pebble Bed Heat Transfer
3.1 Introduction
Effective thermal diffusivity and conductivity are two crucial parameters to determine
inherent safety in porous pebble bed of High Temperature Gas-cooled Reactor. In the
Institute of Nuclear and New Energy Technology, Tsinghua University, a full-radiusscale heat test facility has been developed to measure these thermal properties at hightemperatures. Two vacuum tests and two atmospheric-pressure helium tests up to
1200
◦ C have been conducted to determine the temperature-dependent parameters
by the inverse method of heat transfer. Repeatable results have been verified in both
tests with different heating processes. Furthermore, the primary experimental errors
from installation positions of thermocouples, as well as random packing effect are
reduced by retrieving positions in the inverse method. Sensitivity and uncertainty
analyses are carried out in each test to give a reasonable description of the results of
effective thermal diffusivity and conductivity in these tests. The correct knowledge
on effective thermal diffusivity and conductivity of pebble bed inside the reactor core
is significant to ensure the valid design and inherent safety, which will give a better
balance between safety and economic competitiveness.
3.2 Experimental Facility and Methodology
3.2.1 Configuration of Heat Test Facility
Figure (3.1a) shows an overview of the whole heat test facility. The test facility is
constructed as a cylindrical steel vessel with 5 m in diameter and 7 m from ground
to its header. The water jacket is embedded in the steel vessel, and four mechanical
vacuum pumps maintain the 20Pa vacuum in the same period. Center assembly in
the pebble bed is a graphite heater manufactured based on the power requirement
© Tsinghua University Press 2021
S. Jiang et al., Multiphase Flow and Heat Transfer in Pebble Bed Reactor Core,
https://doi.org/10.1007/978-981-15-9565-3_3
121
Experiments in Pebble Bed Heat Transfer
3.1 Introduction
Effective thermal diffusivity and conductivity are two crucial parameters to determine
inherent safety in porous pebble bed of High Temperature Gas-cooled Reactor. In the
Institute of Nuclear and New Energy Technology, Tsinghua University, a full-radiusscale heat test facility has been developed to measure these thermal properties at hightemperatures. Two vacuum tests and two atmospheric-pressure helium tests up to
1200
◦ C have been conducted to determine the temperature-dependent parameters
by the inverse method of heat transfer. Repeatable results have been verified in both
tests with different heating processes. Furthermore, the primary experimental errors
from installation positions of thermocouples, as well as random packing effect are
reduced by retrieving positions in the inverse method. Sensitivity and uncertainty
analyses are carried out in each test to give a reasonable description of the results of
effective thermal diffusivity and conductivity in these tests. The correct knowledge
on effective thermal diffusivity and conductivity of pebble bed inside the reactor core
is significant to ensure the valid design and inherent safety, which will give a better
balance between safety and economic competitiveness.
3.2 Experimental Facility and Methodology
3.2.1 Configuration of Heat Test Facility
Figure (3.1a) shows an overview of the whole heat test facility. The test facility is
constructed as a cylindrical steel vessel with 5 m in diameter and 7 m from ground
to its header. The water jacket is embedded in the steel vessel, and four mechanical
vacuum pumps maintain the 20Pa vacuum in the same period. Center assembly in
the pebble bed is a graphite heater manufactured based on the power requirement
© Tsinghua University Press 2021
S. Jiang et al., Multiphase Flow and Heat Transfer in Pebble Bed Reactor Core,
https://doi.org/10.1007/978-981-15-9565-3_3
121