Experimental study of a water-based titanium oxide nanofluid in a circular pipe with transition flow and conical strip inserts

The heat transfer characteristics of a horizontal circular tube in a transition regime with conical strip inserts are determined experimentally. A water-based titanium oxide nanofluid was employed as a heat transfer fluid and was prepared using a two-step method with the volume concentration of 0.1 vol.% and 0.5 vol.%. Staggered and nonstaggered conical strips having three different twist ratios are employed. It was observed that the heat transfer performance of the nanofluids increases with the particle volume fraction. Moreover, the heat transfer performance increased enormously with the use of conical strip inserts in comparison with a plain tube. It was also observed that the strip geometry and nanofluid had a major effect on the thermal performance of the circular tube. The maximum Nusselt number was achieved using the staggered type of strips for both forward and backward directions at the Reynolds number 5790.3 with 0.5 vol.% concentration and at a twist ratio of 5 of a conical strip insert. © 2018 by Begell House, Inc.