Hermanson, JamesMurthy, Shuba2025-10-022025-10-022025-10-022025Murthy_washington_0250O_28480.pdfhttps://hdl.handle.net/1773/53890Thesis (Master's)--University of Washington, 2025Cryogenic boiling plays a pivotal role in propulsion and thermal management systems, where efficient heat transfer is essential. Enhancing nucleate boiling through surface modifications has emerged as a promising passive technique to improve heat flux. Building on prior work by Andrew et al., which demonstrated improved performance using axially grooved aluminum cylinders, this study investigates the effects of two additional surface treatments: a wider 3 mm groove spacing and a knurled pattern with a 10° pitch angle and 0.03 mm depth. Heat flux was estimated from thermocouple-based temperature profiles using a one-dimensional conduction model, independent of electrical input power. Results show a distinct performance hierarchy influenced by surface geometry: the 2 mm grooved surface (Andrew's) delivered the highest heat flux, followed by the 3 mm grooved and knurled surfaces, which showed reduced performance due to lower nucleation site density and altered wetting dynamics. These findings highlight the sensitivity of cryogenic boiling to fine-scale surface geometry and support ongoing development of optimized surface designs for advanced cryogenic systems. Imaging techniques have also been investigated to obtain optical data.application/pdfen-USnoneAerospace Heat TransferCryogenicsHeat FluxNucleate BoilingAerospace engineeringFluid mechanicsAeronautics and astronauticsThesis