The effect of boiling in a thermosyphon on surface tension and contact angle of silica and graphene oxide nanofluids

Thermosyphons are heat transfer devices characterised by high efficiency due to simultaneous phase changes occurring in the evaporation-condensation cycle of working fluid. One most promising solutions enhance their capacity device is use nanofluids – suspensions particles with at least one dimension below 100 nm. It was determined that nanofluid does not influence work thermosyphons condenser section and focus should be put on boiling process evaporator section. During boiling, nanoparticles tend deposit heater’s surface, what alters characteristics this surface near hydrodynamics. This appearance nanofluid, but precise effect how deposition affects properties unknown. Changes tension wettability affect regimes (e.g. reduced reduces size departing bubbles inhibits geysering), through device. Understanding those parameters crucial for development appropriate models describing thermosyphon nanofluids. The main goal study determine contact angle based silica nano-sized graphene oxide flakes before after experimental thermosyphon. Results show that, comparison water, (2 vol%) lower angles both analysed surfaces. After-use exhibited noticeably higher averaged smaller fresh medium. change likely decreased concentration caused during operation. Still, differences between before-use after-use samples were than measurement uncertainties. Before-use already showed similar water low (0.1 g/L). Consequently, fluid also much different from water. Additional measurements without addition sodium dodecyl sulphate surfactant allowed differentiate effects surfactant. case pure