Heat Transfer Controlled Collapse of a Cylindrical Vapor Bubble in a Vertical Isothermal Tube

Abstract

An experimental program was conducted to determine the collapse rate of slug-type vapor bubbles rising due to buoyancy through subcooled parent liquid in a vertical isothermal tube. The experimental apparatus included a vertical glass tube with an outer glass container providing a constant temperature water bath for the inner tube. The inner tube contained distilled, deaerated water, and water vapor bubbles were generated at the bottom of this tube with a pulsed electric heater. The parent liquid was uniformly subcooled with respect to the vapor bubble resulting in heat transfer controlled bubble collapse. Collapse rates and rise velocities were recorded by high-speed motion picture photography. Over a limited range of subcooling, the bubble collapse was well behaved, and a simple, quasi-steady boundary layer heat transfer analysis adapted from slug flow over a flat plate correlated the experimental results with a high degree of accuracy. Experimental results were obtained with tubes having inside diameters of 0.0127, 0.0218, and 0.0381 m and for a range of subcooling from 0.5 to 9.0 K.