Enhancement of heat transfer in subcooled flow boiling with microbubble emission

Subcooled flow boiling of water was tested for a large heating surface of 5 cm length and 2 cm width in a horizontal rectangular channel of 5 mm height and 24 mm width. Microbubble emission boiling occurred in transition boiling at 40 K of liquid subcooling and 0.5 m/s of liquid velocity and the maximum heat flux was higher than the ordinary critical heat flux. Maximum heat flux obtained was 5 MW/m2. In subcooled pool boiling of alcohol-water mixtures, critical heat fluxes were higher than that of water, especially, polyhydric alcohol-water mixtures such as 1-butanol and 2-propanol showed about 50% higher critical heat fluxes than water. In the subcooled flow boiling with small heating surface of 10 mm × 10 mm, microbubble emission boiling occurred in transition boiling and the maximum heat fluxes were 10% higher than the water.