ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-472-4
ISBN Online: 978-1-56700-471-7
3rd Thermal and Fluids Engineering Conference (TFEC)
Void Fraction Distribution and Mass/Energy Transfer Characteristics in Rod Bundle
Resumo
Subcooled boiling heat transfer, which is related to Departure from Nucleate Boiling (DNB), is highly concerned
in fuel assembly of Pressurized Water Reactor (PWR). It is of importance and significance to predict void
fraction and mass/energy transfer characteristics among sub-channels under subcooled boiling with 3-D CFD
code to obtain more details for better understanding of two-phase flow process in rod bundle. To better
understand and predict void distribution and its transportation characteristics in rod bundle, two-phase flow
simulation with two-fluid model was carried out with Heat Partitioning Model. In this study, the 5×5 full length
rod bundle of NUPEC PWR Sub-channel and Bundle Test (PSBT) with Uniform-Axial Power Distribution (UAPD)
was used under prototype condition (test serial of B5 configuration) to test the physical method. The
parameter distribution in axial and radial orientation among different sub-channels at the downstream of the last
Mixing Vane Grid (MVG), where the DNB occurs at the end of the heated section, was studied. Different void
fraction distribution was observed among central channels, side channels and corner channels. It is induced by
different mass transfer process results from the layout of mixing vanes. Moreover, the intensity and direction of
mass transfer process shows as a dominant effect on the void fraction distribution and development among subchannels.
Energy transfer is related to the mass transfer among sub-channels. The development of two phase
flow at the downstream of MVG and SSG indicate that the simple support grid (SSG) draws into a suppression
of radial transverse flow and of mass transfer process, which are introduced by the mixing vanes for heat transfer
enhancement.