Abstract
Laminar-turbulent transition flow can be observed in the thermal engineering applications, while the flow resistance and heat transfer characteristics were not fully understood. In this work, the flow and heat transfer for laminar-turbulent transition in the rectangular channel were predicted by a four-equation transition turbulent model. A set of correlations for heat transfer coefficient in the rectangular channel were developed and implemented into the RELAP5/MOD3.1 code to make it capable for the analysis of plate-type fuel assembly with rectangular coolant channel. The improved RELAP5/MOD3.1 code was employed to analyze the SBLOCA along with SBO scenario for an integrated pressurized reactor, illustrating the effects of model modification on the evolution of the accident.
Highlights
Rectangular channels have been widely used in thermal engineering applications, such as nuclear reactors with a plate-type fuel element (Tian et al, 2018) and high-efficiency heat exchangers (Xu et al, 2018), due to their characteristics of high heat transfer capacity and easy manufacture
Most heat exchangers operate in the regime of turbulent flow to reach a high heat transfer coefficient; there are still many heat exchangers that operate in the laminar-turbulent transition regime
Two new subroutines for heat transfer and flow resistance in the rectangular channel are added to the RELAP5 code and are named “dittusrectangular” and “fwdragrectangular.”
Summary
Rectangular channels have been widely used in thermal engineering applications, such as nuclear reactors with a plate-type fuel element (Tian et al, 2018) and high-efficiency heat exchangers (Xu et al, 2018), due to their characteristics of high heat transfer capacity and easy manufacture. Silin et al (2010a,b) carried out experimental work to study the heat transfer characteristics in the laminar to turbulent transition regime for water flowing in a rectangular channel. Based on these experimental and theoretical investigations, the heat transfer and flow resistance correlations can be developed. The mechanisms for the laminar-turbulent transition were not well-resolved from the experimental work, and the current system analysis codes cannot predict the heat transfer and flow resistance characteristics for laminar-turbulent transition flow, they are significant for the design and safety analysis of nuclear power plants. The governing equations for the transition SST turbulent model are given as (ANSYS Inc., 2017):
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