Investigation of volume fraction of nanoparticles effect and aspect ratio of the twisted tape in the tube

In present study, the heat transfer of laminar and turbulent flow of water/Al2O3 nanofluid in the volume fraction of phi = 0-4% of solid nanoparticles in Reynolds numbers of 500-25,000 have been numerically investigated. The studied geometrics is a three-dimensional tube with the diameter of D = 2 cm and the length of L = 50 cm. In order to increase the heat transfer inside horizontal tube, the twisted tape in different aspect ratios has been used. In this research, the considered geometrics with aspect parameters, such as the twisted ratios (P/W) of 3, 3.5 and 4, the space ratios (C/D) of 0.3, 0.4 and 0.5 and the tape width ratios (W/D) at the range of 0.5-0.9, has been investigated. The results indicate that, in the turbulent flow, the use of solid nanoparticle in higher volume fractions and Reynolds numbers, comparing to the laminar flow, improves heat transfer. The existence of solid nanoparticles in lower twisted ratios (P/W) has great effect on the heat transfer enhancement. In the laminar flow, by increasing the width of twisted tape and the concentration of nanoparticles, heat transfer enhances.