Experimental research of bubble characteristics in narrow rectangular channel under heaving motion

Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. Although numerous works have been done on two-phase flow phenomena, most of these works focus on land-based channels. Therefore, for identifying the heat transfer phenomena in the barge-mounted system, it is necessary to know the local flow condition in an oscillating acceleration field. In this study, forced convection subcooled water boiling experiments are conducted in narrow rectangular channels at low frequency oscillations. The bubble size, bubble velocity and bubble number density have been statistically analyzed under different heaving conditions and at different flow rates. The results of the bubble size distribution have been presented as cumulative distribution functions, which exhibit in reality a very wide spread of bubble size. The results show that an increase of the oscillation frequency causes an increase fluctuation of bubble size, bubble velocity and bubble number density. Under the same heaving condition, an increase of mass flow rate leads to a decrease fluctuation of bubble size and bubble velocity. A correlation has been sought for the fluctuation of bubble diameter due to heaving motion. The proposed model agrees well with the experimental data within the averaged relative deviation of ±19.2%. (authors)