Thermal performance enhancement studies on a circular finned coil-in-shell heat exchanger using graphene oxide nanofluid

The objective of this study is to investigate the effect on heat transfer augmentation by the combined effect of circular fins directly attached to the helical surface of the coil in two different orientations (45 degrees and 90 degrees) and Graphene Oxide nanofluid as a heat transport agent, in a coil-in-shell heat exchanger. The attached circular fins not only act as turbulators on the shell side but could also add to heat transfer from the hot side to the cold side, by a combined mechanism of conduction and convection.The experiment is conducted at constant heat flux, with the cold nanofluid in the coil side and hot air in the shell side. Test runs are taken by varying hot air velocities from 1 m/s to 5 m/s, keeping fixed volume concentration of nanofluid (0.05-0.15%) and flow rate (500 <= Re <= 5500) one at a time. Experimental results indicated significant enhancement in heat transfer performance for the finned configuration. For 90 degrees and 45 degrees fin orientation-0.15% volume concentration of nanofluid, the maximum heat transfer increase is by 78.46%, and 82.22%, Nusselt number increase is by 32.57%, 60.79% respectively, at a hot air velocity of 3 m/s. The coil side pressure drop and friction factor increased to 32.72% and 24.64% for 0.15% GO nanofluid when compared to pure water at the maximum flow rate. The thermal-hydraulic performance improvement is nearly two-fold with 45 degrees fin orientation-GO nanofluid combination. [GRAPHICS] .