Enhancement of Pool Boiling and Critical Heat Flux in Self-Rewetting Fluids at Above Atmospheric Pressures

Abstract

Pool boiling experiments have been conducted with a self-rewetting fluid consisting of an aqueous butanol solution to study the boiling heat transfer enhancement at pressures of 1 ∼ 4 bars. Although self-rewetting fluids have been used to enhance the performance of heat pipes, boiling heat transfer characteristics are yet to be fully understood especially at pressures above atmospheric. Pool boiling experiments with aqueous butanol solutions were performed using an electrically heated platinum wire to obtain pool boiling heat transfer data up to the Critical Heat Flux (CHF). Aqueous butanol solutions with butanol concentrations 2–7% showed enhanced heat transfer coefficients and CHF data at various pressure levels. In comparison to water, aqueous butanol solutions showed 20–270% higher values of CHF at pressures up to 4 bars. The bubble sizes were also observed to be significantly smaller in self-rewetting fluids compared to those in water at the same pressure. This observation was consistent even at higher pressures. However, for the highest butanol concentration tested (7%), the CHF enhancement was diminished at higher pressures.