Growth rates of free vapor bubbles in liquids at uniform superheats under normal and zero gravity conditions

Abstract

Extensive experimental data is presented for growth rates of vapor bubbles in water, ethanol, and isopropanol at small uniform superheats up to 4.9°C The measured phase growth occurred in the free volume of the liquid away from solid surfaces and at a nominal pressure level of 1 atm. Uniform, essentially constant superheats were obtained by a pressure release technique. Initial observation times for most bubbles occurred at about 1 ms. Final observation times as large as 450 ms were achieved Comparison of growth data taken at normal gravity to data taken at zero gravity, using a small drop tower, clearly show the point at which effects due to bubble translational motion become significant A detailed comparison is made to Scriven's exact solution for spherically symmetric, heat transfer controlled phase growth. Good agreement is obtained for the rnzero- g data over the entire observation time, while the agreement for the normal- g data is satisfactory up to times at which effects of the buoyant force become significant An interpretation that the increased growth rates observed at later times is due to bubble translational effects is supported by a semi-quantitative comparison to an approximate theory due to Aleksandrov et al. Previous experimental results for bubble growth under uniform, essentially constant superheat conditions and their relation to the present work are also discussed.