Experimental research on transient critical heat flux in vertical tube under oscillatory flow condition

• Published in: International journal of multiphase flow Vol. 37; no. 9; pp. 1235 - 1244
• Main Authors: Zhao, D.W., Su, G.H., Liang, Z.H., Zhang, Y.J., Tian, W.X., Qiu, S.Z.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-11-2011; Elsevier
• Subjects: Applied sciences; Continuous dryout; Critical heat flux; Droplets; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Flow oscillation; Fluctuation; Heat flux; Heat transfer; Inlet flow; Installations for energy generation and conversion: thermal and electrical energy; Liquid films; Oscillations; Periodic dryout; Theoretical studies. Data and constants. Metering; Tubes; Continuous dryout; Periodic dryout; Flow oscillation; Critical heat flux; Flow boiling; Two phase flow; Instrumentation; Critical heat flow; Experimental study; Boiling; Vertical tube; Nuclear reactor; Dry out; Oscillating flow; Thermohydraulics; Heat transfer
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/j.ijmultiphaseflow.2011.06.012

► We conducted critical heat flux experiments with sinusoidal inlet flow oscillation. ► Periodic dryout results in wall temperature fluctuations during post-periodic dryout. ► Long-playing periodic dryout could significantly pre-trigger continuous dryout. ► We proposed a periodic dryout heat flux correlation for oscillatory flow.
The transient critical heat flux (CHF) experiments with forced sinusoidal inlet flow oscillation (oscillation period in 1–11
s, normalized amplitude of inlet flow oscillation in 0–3.0) were conducted in a vertical tube under low pressure condition. To analyze the triggering mechanism and aftermath of periodic dryout, the wall temperature fluctuation characteristics at the onset of periodic dryout and during post-periodic dryout were investigated. Under inlet flow oscillation condition, periodic dryout would be triggered at the wave trough of liquid film oscillation as wall heat flux far below the stable-flow CHF. The transient periodic dryout would give rise to temperature fluctuations on the tube wall, the amplitude of which increased with oscillation period and heat flux. The large wall temperature fluctuation during long-playing periodic dryout could significantly pre-trigger continuous dryout. The changing trends of the periodic dryout heat flux show a reasonable agreement with Okawa’s theoretical model, in which the liquid film oscillation was supposed be weakened by the axial mixing of liquid film. Moreover, the droplet entrainment at the oscillatory interface also has noticeable influence on the oscillation characteristics of liquid film. Based on the analysis of parameter effects on periodic dryout, a semi-empirical correlation was proposed to predict the periodic dryout heat flux under inlet flow oscillation condition.