Evaluation of Exerting Force on the Heating Surface Due to Bubble Ebullition in Subcooled Flow Boiling

Vibration characteristics of subcooled flow boiling on thin and long structures such as a heating rod were recently investigated by the author. The results show that the intensity of the subcooled boiling-induced vibration (SBIV) was influenced strongly by the conditions of the subcooling temperature, linear power density and flow velocity. Implosive bubble formation and collapse are the main nature of subcooled boiling, and their behaviors are the only sources to originate from SBIV. Therefore, in order to explain the phenomenon of SBIV, it is essential to obtain reliable information about bubble behavior in subcooled boiling conditions. This was investigated at different conditions of coolant subcooling temperatures of 25 to 75°C, coolant flow velocities of 0.16 to 0.53m/s, and linear power densities of 100 to 600 W/cm. High speed photography at 13,500 frames per second was performed at these conditions. The results show that even at the highest subcooling condition, the absolute majority of bubbles collapse very close to the surface after detaching from the heating surface. Based on these observations, a simple model of surface tension and momentum change is introduced to offer a rough quantitative estimate of the force exerted on the heating surface during the bubble ebullition. The formation of a typical bubble in subcooled boiling is predicted to exert an excitation force in the order of 10-4 N.

Authors:

• M. R. Nematollahi

Keywords:

• Subcooled boiling
• vibration mechanism
• bubble behavior.

References:

[1] Omatskii, A.P. and Vinyarskii, L.S., 1965, "Critical Heat Transfer in the
Forced Motion of Under heated Water-Alcohol Mixtures in Tubes of
Diameter 0.5mm", Teplofizika Vyskikh Temperature (High
Temperature), Vol. 3, No. 6, pp. 881-3.
[2] Zhou Tao, Wang Zenghui , Yang Ruichang, 2005, "Study on model of
onset of nucleate boiling in natural circulation with subcooled boiling
using unascertained mathematics", in Nuclear Eng. And Design.
[3] Sakurai, A., 2000, "Mechanisms of transitions to film boiling at CHFs in
subcooled and pressurized liquids due to steady and increasing heat
inputs", in Nuclear Eng. And Design.
[4] Nematollahi, M.R., Toda, S. and Hashizume H., 1998, "Characteristic
Phenomena of Subcooled flow boiling Instability", Proceeding of the 6th
Int. Conference on Nuclear Engineering (ICONE6), Paper No. 6403.
[5] Nematollahi, M.R.., Toda, S. and Hashizume, H., 1998, "Vibration
Characteristic of Subcooled flow boiling Instability", 1st European-
Japanese Two-Phase flow Group Meeting, and 36th European Two-
Phase flow Group Meeting, Portoroz, Slovenia Jun 1-5.
[6] Nematollahi, M.R., Toda, S., Hashizume, H. and Yuki, K., 1999,
"Vibration Characteristic of Heated Rod induced by Subcooled flow
boiling", Journal of Nuclear Science and Technology, Vol. 36, No. 7, pp.
575-583.
[7] Bergles, A.E., 1964, "In Influence of Flow Vibration on Forced-
Convection Heat Transfer", Transaction of the ASME, J. of Heat
Transfer, Vol. 107, pp. 559-560.
[8] Takahashi, K. and Endoh, K., 1990, "A New Correlation Method for the
Effect of Vibration on Forced-Convection Heat Transfer", J. of
Chemical Engineering of Japan, Vol. 23, pp. 45-50.
[9] Smimov, H.F., Zrodnikov, V.V. and Boshkova, I.L., 1997,
"Thermoacoustic Phenomena at Boiling Subcooled Liquid in Channels",
Int. J. Heat & Mass Transfer, Vol. 40, No. 8, pp. 1977-1983.
[10] Celata, G.P., Dell Orco, G. and Gaspari, G.P., 1995, "Detection of
Subcooled Boiling Heat Transfer Regimes up to Critical Heat Flux by
Acceleration Equipment", Fusion Engineering and Design, Vol. 28, pp.
44-52.
[11] Nematollahi, M.R., Hashizume, H., and Toda, S., 1998, "The Heated
Rod Vibration in Different Heat Transfer Regimes", 1998 Fall Meeting
of the Atomic Energy Society of Japan, Paper No: G16, pp.410.
[12] Nematollahi, M.R., 1999, "Fundamental Study of Vibration Induced by
Subcooled flow boiling", Ph.D. thesis, Tohoku University, Japan.
[13] Toda, S., and Nematollahi, M.R., 2000, "Heat Transfer Mechanism of
Subcooled flow boiling According to High-speed Photography Results
of a Heating Surface", Second Japanese-European Two-Phase Flow
Group Meeting, September 25-29, Tsukuba, Japan.
[14] Rinehart J.S. and Pearson J., 1963, "Explosive working of metals",
Oxford, Pergamon Press.
[15] Del Valle M.V.H. and Kenning D.B.R., 1985, "Subcooled flow boiling
at High Heat Flux", Int. J. Heat & Mass Transfer, Vol. 28, pp. 1907-
1920.