Gold-in-water nanofluids in microchannels: Surfactant effect

Heat transfer and pressure drop performance of gold-in-water nanofluids in microchannels are experimentally investigated. Gold nanoparticles are suspended in de-ionized (DI) water. The nanofluid stability is maintained by polyvinylpyrrolidone (PVP) for over 4 years. Nanofluids are tested in rectangular, MEMS produced copper microchannels of 70 µm x 50 µm cross-sectional area in a very low Reynolds number range of 30 < Re < 50. The performances of DI-water, PVP added DI-water, and gold-in-water nanofluid with added PVP are compared. The nanofluids always yielded a higher heat transfer coefficients than PVP-DI water solution. For occasional combinations of the particle size, volumetric concentration and flow rate, gold nanofluids yielded higher heat transfer coefficients compared to DI water as well. The effects of flow rate and particle size on the figure of merit (FM) are presented. The study is rare in dealing with pure metals (gold), and is important in emphasizing the surfactant effects on stable duration of nanofluids, and their thermal performance.