turbulent pulsating nanofluids flow and heat transfer inside constant heat flux boundary condition helical-coil tube

Heat transfer enhancement has been the goal of many researches carried out over the past three decades. employing the modified fluids, changing the flow geometry, and active methods are among the commonly used techniques. the effects of three referred techniques, employing pulsation flow as active method, nanofluids instead of conventional fluid as modified fluids and helicalcoil tube as changing the flow geometry on the fluid flow and heat transfer have been investigated numerically. the results of interests with pulsation flow and nonpulsation flow have been presented. in this research, the results indicated that, the coil pitch tube and coil diameter have a minor effect on the nusselt number (5 and 7%, respectively). but the reynolds number has a major effect on the nusselt number, so that by increasing the reynolds number from 5000 to 100000, the nusselt number will be enhanced by more than 200%. the nanofluid pressure drop and heat transfer coefficient increased with nanoparticles volume fraction. in addition, by introducing a concept as the performance evaluation criteria, the mutual effects of the pressure drop and nusselt number were investigated with referred concept. performance evaluation criteria revealed that employing the nanofluid in lower reynolds numbers yields higher effects on the fluid flow and heat transfer.