Heat transfer from the surface of a steam bubble in turbulent subcooled liquid stream

Turbulent heat transfer coefficients have been measured at the surface of single bubbles formed by injecting steam into a subcooled water stream at atmospheric pressure. Depending upon the steam flow rate (0.4 to 1.5 g./min), the water temperature (80° to 180°F.), and the water velocity (0.9 to 7.2 ft./sec.) the bubbles ranged from small, smooth, ellipsoidal bubbles, similar to those observed in highly subcooled nucleate boiling, to large, irregular bubbles which oscillated in size. The bubble frequencies were in the range 200 to 2,500 cycles/sec. and the surface heat transfer coefficients 13,000 to 320,000 B.t.u./(hr.) (sq. ft.) (°F.). Because of these exceptionally high heat transfer coefficients a significant fraction of the total heat flow in Gunther's subcooled boiling experiments is estimated to be attributable to latent heat transport.