Comparative Thermal Performance of Downdraft and Updraft Forced Convection in a Representative 3×3 Pwr Fuel Assembly
Abstract
A plethora of theoretical, numerical, and experimental investigations have relied on updraft forced convection of operating fuel assemblies for light water-cooled fuel assemblies. the inertial scales of turbulence in updraft flow through PWR fuel assemblies are primarily influenced by upstream mixing patterns within the lower plenum and consequent acceleration of flow through the lower core and support plates into the bottom nozzles. in secondary heat transfer applications such as steam generation, recuperation and economization, downdraft flow is utilized to retrieve maximal sensible heat from the primary coolant. Sub-channel volumes aligned vertically could also benefit from force of gravity in developing turbulent flows. a large reduction in pumping power, associated cost of operation and maintenance, and improved balance of plant is suggested to be possible through downdraft forced convection in PWR-type reactors. This article explores the impact of downdraft forced convection within the well-studied 3x3 sub-channel within a range of 20 hydraulic diameters across a representative intermediate flow mixing grid. a range of inflow Reynolds number from 10,000 to 60,000 is simulated over a range of equivalent heat loads of 20% to 100% spanning 20 hydraulic diameters. the fuel rods are represented in true geometric detail, and a constant-value heat profile is assumed for the investigation. at each inflow condition, the turbulence intensity, peak velocity, local heat transfer coefficient, peak wall heat flux, and peak wall temperature are collected across the sub-channel and compared with an updraft configuration evaluated at the same conditions.
Recommended Citation
V. M. Rao and J. D. Smith, "Comparative Thermal Performance of Downdraft and Updraft Forced Convection in a Representative 3×3 Pwr Fuel Assembly," Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2023, pp. 1105 - 1120, American Nuclear Society, Jan 2023.
The definitive version is available at https://doi.org/10.13182/NURETH20-40604
Department(s)
Chemical and Biochemical Engineering
Keywords and Phrases
3x3; CFD; coefficient; downdraft; intensity
International Standard Book Number (ISBN)
978-089448793-4
Document Type
Article - Conference proceedings
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 American Nuclear Society, All rights reserved.
Publication Date
01 Jan 2023
