Thermal-Hydraulics and CFD Codes
Thermal-hydraulic and computational-fluid-dynamics codes predict how coolant removes heat from fusion components and keeps temperatures within limits.
Removing the heat
Fusion components absorb intense heat from plasma radiation, particle flux, and neutron deposition. Thermal-hydraulic codes model how coolant flowing through channels removes that heat, predicting the temperatures of the structure and the coolant. If temperatures exceed material limits, the component fails, so this analysis is a hard design constraint.
From system codes to CFD
- System thermal-hydraulic codes treat flow as one-dimensional networks of channels, fast and suited to whole-loop analysis
- Computational fluid dynamics resolves the three-dimensional flow field, capturing turbulence, mixing, and local hot spots
- Conjugate heat transfer couples the fluid to heat conduction in the solid structure
Coupling to nuclear heating
In a fusion blanket, much of the heat is deposited volumetrically by neutrons and gammas throughout the material, not just on the surface. Thermal-hydraulic analysis therefore takes a spatial heating map from neutronics as its source term, linking the neutron transport calculation to the cooling design.
Design questions answered
These codes determine coolant flow rates and channel layouts, peak component temperatures, pressure drops across the cooling circuit, and margins to boiling or other limits. Their results feed structural analysis, since temperature fields cause thermal stress, and feed the overall heat-removal design.
Verification
CFD accuracy depends on the turbulence model, mesh, and boundary conditions, so results are validated against benchmark experiments and checked for mesh convergence. For safety-relevant analysis, code validation against relevant test data is a documented part of the process.
Cooling analysis is essential for high-heat-flux components like the divertor and first wall, and for the breeding blanket where nuclear heating and coolant flow must be balanced.