Numerical investigation of system pressure effect on heat transfer of supercritical water flows in a horizontal round tube
Shang, Z., Yao, Y. and Chen, S. (2008) Numerical investigation of system pressure effect on heat transfer of supercritical water flows in a horizontal round tube. Chemical Engineering Science, 63 (16). pp. 4150-4158. ISSN 0009-2509
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Publisher's URL: http://dx.doi.org/10.1016/j.ces.2008.05.036
The systempressureeffect on heattransfer of supercriticalwater (SCW) flows in ahorizontalroundtube has been studied by using computational fluid dynamics (CFD) technique, aiming for extending previous researches on the buoyancy effect by further investigating the coupling effects of the systempressure and the buoyancy. A commercial CFD software STAR-CD v4.02 has been used for this purpose. Simulation starts with the sensitive study of key issues, i.e. the mesh dependency, the turbulence model influence, and the near-wall treatments. It was found that on baseline mesh of 477 000 elements with near-wall grid resolution of y+=0.2, the simulation using the Speziale nonlinear high Reynolds k–ɛ turbulence model and the Hassid and Poreh near-wall treatment gives the best predictions in comparison with the experimental data. After the validation, further simulations continued to study the systempressureeffect on heattransfer characteristics of SCW flows in ahorizontalroundtube. It was found that when the buoyancy effect is negligible, the systempressure change has significant effects on the heattransfer of the flow. This implied that the SCW physical property variations due to the systempressure change could play some dominate roles on the heattransfer. However, when the buoyancy effect was considerably strong, the systempressure change has less effect on the heattransfer due to the strong influences of the buoyancy force. This finding has indicated that the heattransfer of SCW flows in ahorizontalroundtube was primarily governed by the buoyancy effect as observed by previous researchers, but the systempressure changes could also have some effects that cannot be simply ignored.