Pressure drop and critical mass flux of water flowing upward in a uniformly heated vertical tube

doi:10.16511/j.cnki.qhdxxb.2018.25.039

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Journal of Tsinghua University(Science and Technology) ›› 2018, Vol. 58 ›› Issue (11) : 1021-1028. DOI: 10.16511/j.cnki.qhdxxb.2018.25.039

THERMAL ENGINEERING

Pressure drop and critical mass flux of water flowing upward in a uniformly heated vertical tube

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Abstract

The critical mass flux, G₀, is a key parameter in the design of vertical water wall in once-through boilers. A vertical water wall has positive flow characteristic only when the mass flux inside the parallel tubes is less than G₀. While G₀ has been reported to be 1 000-1 200 kg/(m²·s), there are few studies on the factors influencing G₀ in the literature. This paper presents a hydrodynamic model based on the classical pressure loss computation method and empirical correlations. The model predicts the pressure drop variation for water flowing upward inside a uniformly heated tube at supercritical/subcritical pressures for various heat fluxes, tube lengths and tube inner diameters. The results show that G₀ increases with decreasing heat flux and tube length and decreases with increasing inner diameter.

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vertical water wall / low mass flux / positive flow characteristic / self-compensating characteristic / critical mass flux

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TANG Guoli, GU Junping, WU Yuxin, LI Zhouhang, LÜ Junfu, LIU Qing. Pressure drop and critical mass flux of water flowing upward in a uniformly heated vertical tube[J]. Journal of Tsinghua University(Science and Technology). 2018, 58(11): 1021-1028 https://doi.org/10.16511/j.cnki.qhdxxb.2018.25.039

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