CFD-Informed Spacer Grid Models in the Subchannel Code CTF
- Pennsylvania State University: 137 Reber Building, University Park, PA, 16802 (United States)
- Oak Ridge National Laboratory: P.O. Box 2008, Oak Ridge, TN, 37831 (United States)
- North Carolina State University: 2107 Burlington Laboratory, Raleigh, NC, 27695 (United States)
Data from computational fluid dynamics (CFD) simulations can be utilized to improve the predictive capabilities of the subchannel code CTF. Past work incorporating CFD results into CTF has included accounting for directed crossflow and turbulent mixing between adjacent subchannels. Spacer grids impact fluid flow in various ways, and this work focuses on four spacer grid effects, namely: 1. Directed crossflow; 2. Turbulent mixing; 3. Enhanced downstream heat transfer; 4. Pressure drop correlation. Heat transfer augmentation occurs partially due to the disturbances in the developed flow and from the additional turbulence generated by the presence of obstructions in the fluid flow's path. The boundary layer disruption is caused in part by the newly-directed flow just downstream of the spacer grid vanes. This effect lessens as the distance from the grid increases and the flow returns to its developed state, closer to what would be expected in a bare subchannel. Current plans of this work are to develop a method for incorporating the effects of spacer grids on the heat transfer calculation within CTF. Proposed techniques include the addition of an enhancement factor to the local heat transfer coefficient. The inclusion of CFD data from properly-designed simulations will allow CTF to better predict parameters such as fluid temperatures near spacer grids. Improved pressure loss coefficients for each grid can also be generated using CFD simulations. The heat transfer modification has been studied, with other authors noting correlations which are dependent on grid properties such as the blockage ratio. Parameters considered in this study are the turbulent kinetic energy (TKE) and vorticity. There are currently no models to calculate or store either of these parameters within CTF. When accounting for spacer grid effects in CTF, it is important to not double-count the effects towards two different CTF models. This requires carefully designing CFD simulations around capturing specific phenomena from the grids and being able to apply these CFD results to all appropriate flow conditions. (authors)
- OSTI ID:
- 23042918
- Journal Information:
- Transactions of the American Nuclear Society, Vol. 115; Conference: 2016 ANS Winter Meeting and Nuclear Technology Expo, Las Vegas, NV (United States), 6-10 Nov 2016; Other Information: Country of input: France; 7 refs.; available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (US); ISSN 0003-018X
- Country of Publication:
- United States
- Language:
- English
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