Influence of carbon nanotubes on pressure drop and heat transfer rate of water in helically coiled tubes

Heat transfer rate and pressure drop of CNT/water nanofluid are measured in a helically coiled tube. The tube wall temperature is assumed to be constant and uniform in all experiments. It is known that carbon nanotubes will enhance the heat transfer rate, and increase the pressure drop of the system, simultaneously. A spiral passage of the helically coiled tubes has the same effects on the system. The combined influence of both heat transfer and pressure drop has not been investigated so far (neither numerically nor experimentally). The results revealed that as the curvature ratio rises, the friction factor will increase. The addition of nanotubes to the base fluid augments the heat transfer rate, which continues with increased concentration of nanoparticles. The critical Reynolds number of the spiral tubes is higher than the straight tubes and the addition of nanotubes to the base fluid will increase the Nusselt number, which is also enhanced with augmented nanoparticle concentration.