Preparation and Pool Boiling Characteristics of Silver Nanofluids Over a Flat Plate Heater

Abstract

Silver nanoparticles of 15 nm average size were prepared by sputtering method and were characterized through x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The pool boiling heat transfer characteristics of nanofluids with 0.25%, 0.5%, and 0.75% by weight concentrations of silver nanoparticles suspended in distilled water are compared with that of pure water. Followed by the same concentration of silver nanoparticles in 9.0% weight of sodium lauryl sulfate anionic surfactant compared with that of pure water. The pool boiling heat transfer data were obtained for a 30-mm-square and 0.44-mm-thickness stainless-steel flat-plate heater. Results reveal that the silver nanoparticle enhances the heat transfer coefficient of water. The heat transfer coefficient increases with increase of silver nanoparticles concentration. The highest enhancement has been found to be 1.9 times greater than that of water at a heat flux of 120 kW/m2 with 0.75% of silver nanoparticles in water. In a water–surfactant nanofluid, it has been found 2.5 times greater than that of water at the heat flux of 250 kW/m2 with 0.75% of silver nanoparticles. With further increase in heat flux the enhancement is found to decrease; however, it is always higher than that of water up to the critical heat flux. Furthermore, the critical heat flux decreases in both the water–silver and water–silver–surfactant nanofluid as well, with increase of silver nanoparticles concentration.