| dc.description.abstract | Nowadays, systems based on convective boiling flows are found in a wide variety of industrial applications, such as boiling water reactors, boilers, thermosiphons, heat exchangers, condenser, chemical reactors and some other chemical process units. Such systems take advantage of the high heat transfer rates that a boiling fluid can reach at moderate temperature differences. However, those systems are unfortunately susceptible to thermally induced two-phase flow instabilities, such as Density Wave Oscillations. Thereby, the aim of present research is to perform an experimental investigation on Density Wave Oscillations, focusing on the analysis of the operational parameter effect in the system stability and characteristics of the oscillations. As a result of this investigation, the Ishii-Zuber plane is found to be appropriate to represent the system stability and that the Guido?s criteria cannot be used to estimate the instability threshold. Moreover, the oscillation amplitude monotonically increases by increasing the heat flux until it reaches an asymptote and the period is found to decrease when the amplitude is increased. Finally, a new dimensionless correlation based on amplitude ratio, is proposed as a result of the observed trends. It is found to be very useful, not only correlates well the collected data at the onset of Density Wave Oscillation, but also predicts the maximum amplitude for the given sets of operating conditions. | nb_NO |
