Jet flows from bubbles during subcooled pool boiling on micro wires
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An experimental investigation was conducted on subcooled nucleate boiling on ultra-small wires having diameters of 25–100 μm. High-speed photography and laser PIV (Particle Image Velocimetry) technology were used to visually observe the bubble dynamics. For highly subcooled boiling, at moderate heat fluxes, the bubbles generally remained attached to the micro heating wires and bubble-top jet flows were clearly observed. Smaller bubbles usually had stronger bubble-top jet flows, while larger bubbles seemed to produce multi-jet flows. The structures of the bubble-top jet flows, as well as multi-jet flows, were proposed from the experimental observation. A model was developed to describe jet flow phenomena from bubbles on micro wires. Numerical simulations for bubbles having diameter of 0.03 and 0.06 mm showed that both the bubble-top and multi-jet flows were induced by a strong Marangoni effect due to high temperature gradients near the wire. The predicted velocity magnitudes and flow structures agreed very well with experimental measurements. The bubble size relative to the wire is an important factor affecting the jet flow structure. For a 0.03 mm bubble on a 0.1 mm wire, only a bubble-top jet flow forms, while a complex multi-jet flow pattern forms around the bubble with a weak bubble-top jet and two side jet flows for a 0.06 mm bubble.
Keywordssubcooled boiling bubble multi-jet jet flow PIV Marangoni CFD
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- 1.Dhir, V. K., Nucleate and transition boiling heat transfer under pool boiling and external flow conditions, in Proc. 9th Int. Heat Transfer Conf., Jeruslem, Israel, Vol. 1, 1990, 129–155.Google Scholar
- 2.Carey, V. P., Liquid Vapor Phase-Transition Phenomena, New York: Hemisphere Publishing House, 1992.Google Scholar
- 4.Sadasivan, P., Unal, C., Nelson, R. A., Nonlinear aspects of high heat flux nucleate boiling heat transfer: formulation, LAUR-94-2222, also ASME HTD-298, 1994, 91–102.Google Scholar
- 5.Sadasivan, P., Unal, C., Nelson, R. A., Nonlinear aspects of high heat, flux nucleate boiling heat transfer: results LAUR-94-106-Revised, also ASME HTD-298, 1994, 103–114.Google Scholar
- 7.Eddington, R. I., Kenning, D. B. R., The prediction of flow boiling bubble populations from gas bubbles nucleation experiments, in Proceedings of 6th International Heat, Transfer Conference, Toronto, Vol. 1, 1978, 275–279.Google Scholar
- 17.Shekriladze, I. G., On the role of the “Punping effect” of a vapor bubble growing at the wall during nucleate boiling, in Voprosy konvektivnogo teploobmena I chistoty vodianogo para (in Russian), Tbilisi: Metsniereba Press, 1970, 90–97.Google Scholar
- 19.Shekriladze, I. G., Mechanisms of heat, removal in the process of developed Boiling, Heat Transfer-Soviet Research, 1990, 22(4): 445–463.Google Scholar
- 20.Sharp, R. R., The nature of liquid film evaporation during nucleate boiling NASA TND-1997, Oct. 1964.Google Scholar
- 21.Carey, V. P., Liquid Vapor Phase-Transition Phenomena, New York: Hemisphere Publishing House, 1992.Google Scholar
- 22.Paul, B., Complication of evaporation coefficients, ARS Journal, 1962, 32: 1321–1328.Google Scholar