Study of self-rewetting fluid applied to loop heat pipe

Abstract

This study investigated the application of self-rewetting fluid to loop heat pipe (LHP) and its effect on the heat transfer performance of LHP, proposing a most suitable solute and concentration for LHP. At a certain temperature, a self-rewetting fluid, contrary to common newtonian fluids, has the ability to reverse its surface tension's trend, inducing colder fluid to flow to the heated surface and delaying the occurrence of dry-out in LHP during operation. The most important variables for a self-rewetting fluid are its concentration and solute. Thus, this study focused on a few self-rewetting fluids (including butanol, pentanol, and hexanol aqueous solutions); the surface tensions of these fluids at different concentrations were measured to find the best self-rewetting fluid, and then it was applied to LHP as working fluid to investigate its effect on the heat transfer performance.Results of surface tension measurement showed that, concerning the concentration of a self-rewetting fluid, the optimal concentration for a self-rewetting fluid was its saturation concentration; concerning the solute of a self-rewetting fluid, after comparing all the tested working fluids at the optimal concentration, 6% butanol aqueous solution was the best type of self-rewetting fluid. Results from applying 6% butanol to LHP as working fluid for performance testing showed that the critical heat load was 650 W and the total thermal resistance was 0.25 ° C/W. Compared with LHP with regular working fluid, the critical heat load was 2.5 times higher and total thermal resistance decreased by about 60%, indicating high potential for self-rewetting fluids to enhance the heat transfer performance of LHPs.