Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.
Effective thermal conductivity models which can be used to
analyze the heat transfer phenomena of a prismatic fuel block
were evaluated by the experiments. In the accident condition of
VHTR when forced convection is lost, the heat flows in radial
direction through the hexagonal fuel blocks that contain the large
number of coolant holes and fuel compacts. Due to the complex
geometry of fuel block and radiation heat transfer, the detail
computation of heat transfer on the fuel block needs excessive
computation resources. Therefore, the detail computation isn't
appropriate for the lumped parameter code and a system code
such as GAMMA+ adopts effective thermal conductivity model.
Despite the complexity in heat transfer modes, the accurate
analysis on the heat transfer in fuel block is necessary since it is
directly relevant to the integrity of nuclear fuel embedded in fuel
block. To satisfy the accurate analysis of complex heat transfer
modes with limited computing sources, the credible effective
thermal conductivity (ETC) models in which the effects of all of
heat transfer modes are lumped is necessary. In this study,
various ETC models were evaluated with the experiment result.
Experiments for measuring the ETC values of the VHTR fuel
block geometry were conducted with IG-11 graphite block. And
four probable models compared to the experiment result showed
good agreement with them, and thus they could be a candidate
ETC model for VHTR fuel block.