Volume 8, Issue 6 (June 2011)
Boiling Heat Transfer of Butanol Aqueous Solution-Augmentation of Critical Heat Flux
Boiling heat transfer, especially critical heat flux (CHF), of some aqueous solutions is enhanced by adding small amount of alcohol such as butanol. Such aqueous solutions show nonlinear surface tension dependence on liquid temperature and are sometimes called as “Self-rewetting liquid”, being applied recently to thermal devices such as heat pipes. However, the heat transfer characteristics of boiling of self-rewetting liquids are not fully understood. In the present research, by employing butanol aqueous solution as a typical test solution, a fundamental boiling test is performed on a heated wire with special attention to CHF augmentation in order to observe the boiling phenomena and to address the fundamental issues. In the experiment, solution density and liquid subcooling was changed in a wide range. From the experiment, it is found that generating bubbles are very small and large in number and are difficult to coalescence and that the CHF of saturated boiling is enhanced from 2 to 3 times when compared with that of pure water. It is also found that the dependence of CHF on liquid subcooling is peculiar. Namely, with increasing subcooling, CHF decreases first, takes a minimum and then increases.