The team of CFD specialists at Adaptive Research combines experience in
modeling a wide range of fluid flow and heat transfer problems for various
industries, such as biomedical, environmental and aerospace. The group uses
a suite of CFD software tools that effectively model laminar and turbulent
flows, compressible and incompressible flows, Newtonian and non-Newtonian
flows, as well as problems involving heat and mass transfer, chemical
reactions, free surface, particle tracking, radiation, and fluid-structure
Research offers a variety of programs to suit every budget and need.
Engineering contracts typically fall into one of the following categories:
Level I –
one day to several days
Level II – one
week to several weeks
Level III – one month to several
All engineering projects are
accurately scoped and well defined before work commences. Project
deliverables typically include:
Detailed project report
CFD model files and
/ post-processing files and outputs
Excessive air and solid temperatures in spent fuel nuclear storage units can
have catastrophic consequences. It is therefore critical that the cooling
efficiency of such systems is accurately evaluated. Because of the complex
physics involved in predicting local air patterns and heat exchanges inside
the units, Computational Fluid Dynamics methods present significant
advantages to perform a coupled flow and heat transfer analysis.
The current study demonstrates that a numerical solution can provide
detailed temperature distributions on the canister, heat shields and
concrete walls, as well as demonstrate good agreement with experimental
measurements. Because CFD simulations are generally fast and inexpensive,
they open new possibilities to evaluate the design of spent fuel storage
units and improve the overall cooling efficiency of the system.
Spent fuel nuclear storage systems must guarantee sufficient cooling to
prevent excessive air and solid temperatures in the system and therefore
avoid the possibility of catastrophic accidents. Because of the complex
physical processes dictating flow conditions and heat transfer
characteristics inside the unit, analysis requirements must include the
ability to accurately predict free and forced convection, conductive and
radiative heat transfer, and turbulence.
In the current study, special emphasis is placed
on demonstrating that Computational Fluid Dynamics techniques can be used
efficiently to determine local flow patterns in the air passageways and
temperature distributions on the canister surface, heat shields and concrete
walls. The numerical simulation is compared with experimental measurements
reported by Pacific Northwest Laboratory for a 7 kW heating load in an
existing NUHOMS storage system.
The numerical model consists of four primary
components: spent fuel canister, stainless steel heat shield, concrete
enclosure, and air duct passageways. The geometry is decomposed into fluid
and solid sub-regions with a total computational mesh size of approximately
For the purpose of this analysis, air is treated
as an ideal gas and buoyancy effects are included using the Boussinesq
approximation. Turbulent fluctuations in the flow are accounted for by using
a standard k-ε model with appropriate wall function treatment. The relevant
physical properties for the different solid materials (density, thermal
conductivity, and emissivity) are treated as constant over the expected
range of temperatures. The thermal radiation energy exchanges between the
solid surfaces are computed based on a view factor radiative heating model
including internal obstructions.
The 7 kW heating load from the spent fuel is
applied as a constant heat flux on the lateral canister surface and over the
length of the fuel cavity. The axial heat flux through the end caps of the
canister is assumed to be small and is therefore neglected. In this
simplified model of the storage system, the heat exchanges within the
canister, including shell conductivity, are not represented.
The CFD solution is executed using an automatic
local time-stepping method until steady-state conditions are reached. The
CFD software utilized for this analysis, STORM/CFD2000 (owned and developed
by Adaptive Research), solves the full Navier-Stokes equations in a general
curvilinear coordinate system. The code employs a structured grid technique
and is based on a finite volume pressure-based approach applicable for all
flow speeds. The solution scheme is based on a strongly conservative
formulation for the Navier-Stokes equations and uses a modified PISO
Results and Discussion
The CFD simulation provides significant insight
on local flow patterns inside the storage unit, as well as detailed
information on heat transfer characteristics for the entire system.
Temperature distributions for the canister, heat shields, and concrete walls
are shown. Air velocities at the symmetry plane and air temperatures for an
axial cross-section are also presented.
The numerical results shows that for a total
heat load of 7 kW applied evenly over the fuel cavity length, the
temperatures distributions at the symmetry plane are in good agreement with
the experimental measurements. The slight discrepancies observed for the
center region of the canister and concrete walls, as well as at the back end
of the heat shield may be explained by some of the assumptions made in the
numerical model (canister shell conductivity neglected, constant axial heat
flux, no support rails). However, considering the uncertainty in the
experimental data and lack of information on the exact positioning of the
measurement devices, the numerical simulation performed well in predicting
the overall temperature distributions for the storage system.
The numerical solution provides accurate details on local free and forced
convection flow patterns, as well as conductive and radiative heat exchanges
inside the storage unit. The results demonstrate that temperature
distributions on the canister, heat shields and concrete walls are in good
agreement with experimental measurements.
passages and computational mesh.
Canister, shields and
Air velocity and temperature at symmetry