experimental investigation of convective heat transfer of carbon nanotubes / water flow in a helical triple tube heat exchanger

in this work, the thermal performance of cnt/water nanofluid for the heatexchanger with helical triple tubes is investigated experimentally. the geometry of the tube, the volume percentage of nanoparticles, and reynolds number are three key characteristics investigated. twocases with different curvature ratios of 0.010 and 0.0167 are constructed and compared to investigate the impact of the curvature ratio on convection heat transfer. the results show that the nusselt number of nanofluids is larger than the base fluid. in addition, maximum andminimum values of nusselt number are found for reynolds numbers of1000 and 5000 correspondingly. the results show a slight reduction inpressure drop for pure water as the dean number increased. moreover, while the volume fraction of nanoparticles less than 0.1%, the nusselt number increased with a shallow slope.