Numerical analysis of thermal-hydraulic characteristics of steam-air condensation in vertical sinusoidal corrugated tubes

The thermal-hydraulic characteristics of steam-air in the vertical corrugated tubes with sinusoidal waveform condensing wall of various amplitudes and wavelengths under the different inlet velocities, air mass fractions and wall subcoolings are numerically investigated, in the cases that the mass, species, energy and momentum sink terms are added in the cells adjacent to the condensing wall to simulate the condensation process. The mechanisms of turbulent flow and heat transfer enhancement of steam-air in condensation are also explored. The results show that the detached vortex characteristics and accumulated air in waveform domain influence the condensation heat transfer greatly, which are closely related to the amplitude and wavelength of basic waveform as well as inlet velocity. To evaluate the thermal-hydraulic performance of steam-air fluid in the corrugated tubes, the thermal-hydraulic performance factor, phi, describing the relation of heat transfer performance (i.e., ) to pressure drop characteristic (i.e., eta), is defined. The better thermal-hydraulic performance can be obtained in the corrugated tubes with longer wavelength and higher amplitude waveform condensing wall under a low inlet velocity as well as with lower amplitude waveform condensing wall under a high inlet velocity. Besides, the corrugated tubes with A=0.5, 2 mm at L=21 mm respectively in the inlet velocity range of v=2-4 m/s and v=5-12 m/s are the better design of geometric parameters. (C) 2020 Elsevier Ltd. All rights reserved.