ISSN Online: 2377-424X
International Heat Transfer Conference 12
Flow Boiling at Low Mass Flux
Abstract
This paper reports new experimental results for flow boiling of iso-octane in a vertical tube, at low mass flux. The
experiments were carried out over a range of pressures from 2 to 6 bar, mass fluxes from 70 to 300 kg/m2s and heat fluxes from 10 to 50 kW/m2. Under these conditions the slug and churn regimes are expected to dominate. The
results show some distinctive trends of the heat transfer coefficient at near-zero quality, similar to those observed by
previous researchers (Kandlbinder, 1997; Jeglic and Grace, 1965; Ishii, 1982, Cheah, 1995). For the slug flow region
an attempt was made to calculate the heat transfer coefficient using a model where the effect of nucleate boiling along with its suppression by convective flow was taken into account. The model seems to provide predictions, which broadly agree with the experimental results. It fails, however, to predict the more complex trends of increasing and decreasing heat transfer coefficient with respect to vapour quality. In order to explain these more complex trends an alternative hypothesis is advanced.