The current state on the thermal performance of twisted tapes: A geometrical categorisation approach

Abstract

Twisted tapes are used in thermal performance intensification of heat exchangers. The present paper focuses on the last eleven years experimental and numerical studies of the twisted tapes that are inserted into a plain circular horizontal tube with different kind of working fluids such as air, water, nanofluids, high viscosity oil, servotherm medium oil, microencapsulated phase change material slurry, non-Newtonian tomato puree, carboxymethyl cellulose and CuO mixture, lubricating oil. It aims to be a summarising and guiding source with detailed tables, figures, graphs and a criticization for the researchers. Correlation equations of friction and Nusselt number for "plain tube" and "classical twisted tape inserted plain tube" were summarised for laminar/turbulent regimes. Equipment (or used software) list was made, and items were explained for experimental and numerical works. Ranges of some critical parameters were presented from the selected works. Twisted tapes were categorised according to their geometrical designs. Then, performance considerations were made on them (in the category itself) while the flow regimes were also taken into account. Finally, by considering all the geometrical variation groups, the relation between design and performance was tried to be figured out. Some geometrical design suggestions were given for twisted tapes.