TY - GEN
T1 - Direct Numerical Simulation of Low and Unitary Prandtl Number Fluids in a Simultaneously Cooled Vertical Channel
AU - Tai, Cheng Kai
AU - Nguyen, Tri
AU - Merzari, Elia
AU - Bolotnov, Igor A.
N1 - Publisher Copyright:
© 2023 Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023. All rights reserved.
PY - 2023
Y1 - 2023
N2 - Understanding vertical mixed convection of low-to-unitary Prandtl fluids is the backbone to the passive heat removal assessment in the advanced reactors designs. Buoyancy effect could give rise to considerable impact on the convective heat transfer. Currently, there is a need for high-resolution data to support modeling of this complicated phenomenon. A series of direct numerical simulations is carried out to study the low flow mixed convection of liquid metals and unitary Prandtl in a downcomer-representing vertical channel. We further focus on the simultaneous cooling downflow scenario, in which the buoyancy is aligned with the direction of bulk flow. In this scenario, the buoyancy accelerates of the flow within range of thermal boundary layer. The acceleration first caused laminarization of the turbulence and accompanied by the surge of the high-velocity sweep near the walls. The unitary Prandtl fluid was identified to be more susceptible to the buoyancy effect in this case, owing to the inhomogeneity of the temperature across the walls. The laminarization also rendered considerable impairment of convective heat transfer because of the reduced turbulent heat transfer. Also note that the flow regime transition could span across the channel at the low buoyancy cases, which may pose challenge for the turbulence modeling. For the liquid metals, the high thermal diffusivity rendered low temperature difference between the near wall and the bulk fluid. Hence the establishment of the buoyancy effect is more visible at strong buoyancy cases.
AB - Understanding vertical mixed convection of low-to-unitary Prandtl fluids is the backbone to the passive heat removal assessment in the advanced reactors designs. Buoyancy effect could give rise to considerable impact on the convective heat transfer. Currently, there is a need for high-resolution data to support modeling of this complicated phenomenon. A series of direct numerical simulations is carried out to study the low flow mixed convection of liquid metals and unitary Prandtl in a downcomer-representing vertical channel. We further focus on the simultaneous cooling downflow scenario, in which the buoyancy is aligned with the direction of bulk flow. In this scenario, the buoyancy accelerates of the flow within range of thermal boundary layer. The acceleration first caused laminarization of the turbulence and accompanied by the surge of the high-velocity sweep near the walls. The unitary Prandtl fluid was identified to be more susceptible to the buoyancy effect in this case, owing to the inhomogeneity of the temperature across the walls. The laminarization also rendered considerable impairment of convective heat transfer because of the reduced turbulent heat transfer. Also note that the flow regime transition could span across the channel at the low buoyancy cases, which may pose challenge for the turbulence modeling. For the liquid metals, the high thermal diffusivity rendered low temperature difference between the near wall and the bulk fluid. Hence the establishment of the buoyancy effect is more visible at strong buoyancy cases.
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U2 - 10.13182/NURETH20-40391
DO - 10.13182/NURETH20-40391
M3 - Conference contribution
AN - SCOPUS:85202929192
T3 - Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
SP - 1219
EP - 1232
BT - Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
PB - American Nuclear Society
T2 - 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023
Y2 - 20 August 2023 through 25 August 2023
ER -