| Autor: |
Xiaoxu Ma, Taicheng Liu, Nan Dai, Maocheng Tian, Shijie Li |
| Jazyk: |
angličtina |
| Rok vydání: |
2022 |
| Předmět: |
|
| Zdroj: |
Frontiers in Energy Research, Vol 10 (2022) |
| Druh dokumentu: |
article |
| ISSN: |
2296-598X |
| DOI: |
10.3389/fenrg.2022.906809 |
| Popis: |
In this work, the perturbation length of vertical U-bend effects on the air–water two-phase flow in their adjacent straight tubes was investigated experimentally at ambient pressure and temperature. The experimental database covered test sections with three inner diameters of U-tubes (9, 12, and 16 mm), two curvature ratios (8.33 and 12.5), and two orientations (downward and upward). The air and water superficial velocities varied from 0.18 to 25.11 m/s and from 0.11 to 1.98 m/s, respectively. The dissipation of U-bend effects in the regions upstream and downstream of U-bends is characterized by the variation regularities of segmental pressure gradients along the contiguous straight tubes. It was found that the significant value of the dimensionless perturbation length (Lp/D) is less than 60 for the experimental conditions in this study. The influences of the inlet volume void fraction, two-phase mixed Froude number, mixed Weber number, and mixed Dean number on dimensionless perturbation length (Lp/D) are similar. With the increase in these parameters, Lp/D presents a unimodal distribution which first increases and then decreases. The maximum value of Lp/D takes place at a volume void fraction of around 90%. New dimensionless correlations to predict the influence length of U-bends on the straight tubes upstream and downstream have been provided. The prediction errors of 80% of data are within ± 30% compared with the present experimental data. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
|
