Experimental investigation of the effect of graphite-pure water nanofluid use on thermal performance in a heat exchanger

In this study, the effect of the use of nanofluid on heat transfer in order to improve heat transfer under parallel and opposite flow conditions in a concentric and nested tubular heat exchanger whose inner tube is helical type was investigated. The effect of nanofluid obtained by adding nanoparticles to the basic liquid on thermal performance has been investigated experimentally. Water was used as a cold fluid in the study. Water and graphite nanofluid were used as hot fluids, respectively. The hot fluid was sent to the system at constant flow rate and constant temperature. The flow rate of hot fluid to cold fluid is 1, 0.75, 0.50 and 0.25 they were taken and the cold fluid was sent to the system at 3, 4, 6 and 12 l/min flow rates. In the study, the hot water flow rate was taken as constant at 3 l/min and the inlet temperature was taken as constant at 55 °C. The experiment was conducted at room temperature. In the experiment conducted with water, while the fluid was at a flow rate of 3 l/min, the Reynolds number was calculated as 11215.29 under parallel flow conditions and it was found that the flow was turbulent. In studies conducted with nanofluidics, turbulent flow has generally been preferred in the literature. In this study, it was also ensured that the flow was turbulent. Calculations were made and compared using the data, obtained from experiments with pure water and nanofluid. In the whole experiment, data were taken after the system became stable. As a result of the experiment, it was observed that the particles added to the basic liquid increase the heat transfer. It has been determined that the use of graphite/pure water nanofluid increases the heat transfer significantly compared to pure water. In the experiment, the graphite/püre water nanofluid showed a better performance than the basic liquid. The best results in the study, the improvement rate of 23.053% was determined under opposite flow conditions at a hot fluid flow rate of 3 l/min. On the other hand, heat transfer rate improved by 11.657% under parallel flow conditions and 13.498% under opposite flow conditions with the use of graphite/pure water nanofluid.