Proper, John2020-08-252020-08-252020-05https://hdl.handle.net/11299/215023University of Minnesota M.S.M.E. thesis.May 2020. Major: Mechanical Engineering. Advisor: Francis Kulacki. 1 computer file (PDF); ix, 59 pages.Previous research has demonstrated that heat transfer of water may be enhanced by either the addition of surfactants or through emulsifying the water with a small volume of volatile disperse phase. However, the combination of surfactant and emulsion has not yet been thoroughly investigated. To accomplish this, experiments of boiling heat transfer were conducted with dilute FC-72 in water emulsions and Tween-20 surfactant. Boiling occurred over a flat upward-facing aluminum nitride heater in a vessel nearly 1 L in volume. FC72-in-water emulsions with volume fractions of 0.1, 0.5, and 1.0 % were tested with concentrations of 0, 10, 60, and 100 ppm Tween-20 surfactant. Turbulent mixing induced by pumping through a check valve caused the fluid to emulsify. Size distributions of oil droplets in the emulsions were measured via laser diffraction. The resulting boiling curves for emulsion without surfactant confirmed previously observed trends, with an increase in heat transfer occurring near 80 °C. Boiling with Tween-20 surfactant did not show any increase in heat transfer, in both aqueous surfactant systems and emulsions with surfactant. Laser diffraction imaging showed that emulsions with different volume fractions can have different particle size distributions even though the emulsification process was the same. Addition of surfactant to the emulsion tended to cluster the droplet diameter distribution around a mean of 2 µm. The similarity of boiling behavior between mixtures of water and Tween-20 and emulsions with Tween-20 suggests that the boiling behavior is characterized mostly by interface chemistry unique to Tween-20, rather than a secondary effect of droplet size distribution. However, there is considerable variety in surfactants, and there is still value in testing the effect of other surfactants on the boiling behavior of dilute oil-in-water solutions.enEmulsionHeat TransferPool BoilingSurfactantThesis or Dissertation