An emulsion is a system containing two immiscible phases: a dispersed phase and a continuous phase. Components needed to prepare an emulsion are oil, water, surfactant, and energy. The nature of surfactant determines the type of emulsion (oil-in-water (O/W) or water-in-oil (W/O)). A nanoemulsion is an emulsion with 20–200 nm droplet size. The required energy to form a nanoemulsion can be obtained from a mechanical device (high-energy emulsification) or from the chemical potential of the components (low-energy emulsification). High-energy emulsification consists of high-pressure homogenization (HPH), ultrasonication, and microfluidization and low-energy emulsification consists of phase inversion temperature (PIT), phase inversion composition (PIC), and solvent diffusion. O/W nanoemulsions have been studied more than W/O nanoemulsions and the preparation of nanoemulsions with high-energy emulsification is more reported than low-energy emulsification. The small droplet size of a nanoemulsion enhances the emulsion stability; therefore, nanoemulsions have various applications in the industrial field, such as personal care and cosmetics as well as health care, food, and agrochemicals. Pharmacy and cosmetics are fields where more direct applications of nanoemulsions are proposed.

In this paper, geyser boiling phenomenon (GBP) in a two-phase closed thermosyphon has been investigated experimentally. Here, the effects of the inclination angle, filling ratio, input heat rate, mass flowrate of coolant, and inside diameter of the tube on the GBP have been discussed. Three copper thermosyphons with inside diameters of 14 mm, 20 mm, and 24 mm and a length of 1000 mm were employed. Distilled water was used as the working fluid. A series of experiments was carried out to investigate the effect of the inclination angle range of 5° to 90°, the input heat rate range of 50 to 312.4 W, the coolant mass flow rate range of 0.00389 to 0.0164 kg/s, and the filling ratio range of 15 to 45%. The GBP has been investigated by analyzing the time variations of the evaporator and adiabatic wall temperature and outlet water temperature from condenser jacket. The results show that the period of GBP was longer for higher inclination angles and filling ratios. Furthermore, it was discovered that the GBP did not take place for inclination angles of less than 15°.