AUTHOR=Li Xianwen , Su Xingkang , Gu Long , Zhang Lu , Sheng Xin 

TITLE=Numerical Study of Low Pr Flow in a Bare 19-Rod Bundle Based on an Advanced Turbulent Heat Transfer Model

JOURNAL=Frontiers in Energy Research

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2022.922169

DOI=10.3389/fenrg.2022.922169

ISSN=2296-598X

ABSTRACT=<p>Compared to assuming a constant turbulent Prandtl number model, an advanced four-equation model has the potential to improve the numerical heat transfer calculation accuracy of low–Prandtl number <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>P</mml:mi><mml:mi>r</mml:mi></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math></inline-formula> fluids. Generally, a four-equation model consists of a two-equation <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ε</mml:mi></mml:mrow></mml:math></inline-formula> turbulence model and a two-equation <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>k</mml:mi><mml:mi>θ</mml:mi></mml:msub><mml:mo>−</mml:mo><mml:msub><mml:mi>ε</mml:mi><mml:mi>θ</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> heat transfer model. It is essential to analyze the influence of dissimilar turbulence models on the overall calculation accuracy of the four-equation model. The present study aims to study the effect of using different turbulence models on the same <inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>k</mml:mi><mml:mi>θ</mml:mi></mml:msub><mml:mo>−</mml:mo><mml:msub><mml:mi>ε</mml:mi><mml:mi>θ</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> heat transfer model. First, based on the open-source computational fluid dynamics software OpenFOAM, an advanced two-equation <inline-formula id="inf5"><mml:math id="m5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>k</mml:mi><mml:mi>θ</mml:mi></mml:msub><mml:mo>−</mml:mo><mml:msub><mml:mi>ε</mml:mi><mml:mi>θ</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> heat transfer model was introduced into the solver buoyant2eqnFoam, which was developed based on the self-solver buoyantSimpleFoam of OpenFOAM. In the solver buoyant2eqnFoam, various turbulence models built into OpenFOAM can be conveniently called to close the Reynolds stress and an advanced two-equation heat transfer model can be utilized to calculate the Reynolds heat flux of low-<inline-formula id="inf6"><mml:math id="m6" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi><mml:mi>r</mml:mi></mml:mrow></mml:math></inline-formula> fluids. Subsequently, the solver buoyant2eqnFoam was employed to study the fully developed flow heat transfer of low-<inline-formula id="inf7"><mml:math id="m7" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi><mml:mi>r</mml:mi></mml:mrow></mml:math></inline-formula> fluids in a bare 19-rod bundle. The numerical results were compared and analyzed with the experimental correlations and other simulation results to validate the effectiveness and feasibility of the solver buoyant2eqnFoam. Furthermore, the influence of combining different turbulence models with the same two-equation <inline-formula id="inf8"><mml:math id="m8" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>k</mml:mi><mml:mi>θ</mml:mi></mml:msub><mml:mo>−</mml:mo><mml:msub><mml:mi>ε</mml:mi><mml:mi>θ</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> heat transfer model was also presented in this study. The results show that the turbulence model has a considerable influence on the prediction of turbulent heat transfer in the high Peclet number range, suggesting that it should be prudent when picking a turbulence model in the simulations of low-<inline-formula id="inf9"><mml:math id="m9" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi><mml:mi>r</mml:mi></mml:mrow></mml:math></inline-formula> fluids.</p>