Boiling performance on nanostructure coated tubes with water and FC-72

Boiling heat transfer is used in many applications, such as power generation and refrigeration, because of the ability to transfer a large amount of heat energy due to the phase change process. Because of this, much research has been performed to determine different methods and techniques that enhance the performance of the boiling process. Many recent boiling enhancements have been discovered by modifying the boiling surface with nanoscale structures. Much of this research has been performed using small flat boiling surfaces, however most boiling applications typically use tubular geometries instead of flat surfaces. This has led to the motivation of this research-to study how changing from flat surfaces to tubular surfaces affected performance when applying boiling enhancement techniques, which had been initially applied to flat surfaces, to tubular surfaces instead. As such, this work has focused on tube boiling using water as well as FC-72 as the working fluids. This work led to four main findings: the demonstration of a local circumferential temperature variation when boiling with water on a nanostructure coated tube, the finding that applying a nanostructure, which was previously used to increase critical heat flux (CHF) of FC-72 boiling on flat surfaces, to tubes reduces CHF, the discovery of a hereto previously undescribed pulsating secondary flow during boiling with FC-72, and the creation of a new nondimensional number as well as a new combination of nondimensional numbers used to characterize the pulsating secondary flow.