Investigation of graphene based carbon nanofluids and their use in heat exchanger systems

INVESTIGATION OF GRAPHENE BASED CARBON NANOFLUIDS AND THEIR USE IN HEAT EXCHANGER SYSTEMS The nanofluids are the new type of heat transfer fluids that are made by adding nano particulates which have high thermal conductivity to a conventional fluid. Adding nanoparticles to the fluid leads to a significant improvement in heat transfer since the heat capacity of the fluid increases due to the high surface area of the nanoparticles. Among the nano-particulates, nano-carbons are usually preferred as the nanofluids in heating/cooling systems. In this study, it is aimed to produce carbon nanofluid containing single or multilayer graphene with high efficiency and to increase the heat transfer performance of heat exchangers. For the liquid phase exfoliation method, the effects of pretreatment, the amount of the surfactant used and sonication time on the yield were investigated. When the chemical/heat-treated expanded graphite: sodium cholate ratio was 5:1, the yield was obtained as 4.2 % at 12 hours of sonication. Thermal conductivities of the nanofluid in stationary state was determined and these fluids were used as the hot fluid in laboratory-scale double-pipe, counter-flow heat exchanger and heat transfer performance tests were carried out. According to the results, it was found that carbon nanofluid could be used as alternative fluid in heat exchanger systems.