Heat transfer of supercritical CO2 in vertical round tube: A considerate turbulent Prandtl number modification
2020
Du, Xin | Lv, Zhihao | Yu, Xiao | Cao, Maoguo | Zhou, Jianjun | Ren, Yongxiang | Qiu, Qinggang | Zhu, Xiaojing
In order to predict the heat transfer deterioration (HTD) of supercritical pressure fluids and to provide practical guidance for engineering applications of supercritical pressure CO₂ (SC-CO₂), a considerate turbulent Prandtl number (Prₜ) modification was proposed with the use of shear stress transport k−ω turbulent model. The proposed variable Prₜ model considering the effects of system pressure, fluid properties and tube diameters was validated by comparing with 26 reported experimental data, especially for HTD cases. The comparison results show that the present model not only predicts the HTD but also reproduces the onset of it. The modification of Prₜ in the buffer layer is the key to predict the wall temperature accurately, since the modified Prₜ changes in association with the molecular Pr and accommodates the contribution rate of molecular conduction to turbulent mixing on heat transfer. Moreover, the correction factors for tube diameter and system pressure are implemented to adjust the modification of Prₜ. The applicability of the proposed model to various operating conditions is verified in this paper, therefore the present modification for Prₜ may be popularized to extensive engineering applications of SC-CO₂, especially for the optimization design of SC-CO₂ heat exchanger.
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