Performance assessment in a tube with rotor-assembled strands mixed by spiral ladder rotor and low flow resistance rotor

The article presents an experimental study of turbulent heat transfer and friction characteristics in a circular tube equipped with single spiral ladder rotor (SLR)-assembled strand, single low flow resistance rotor (LFR)-assembled strand and rotor-assembled strands mixed by spiral ladder rotor (SLR) and low flow resistance rotor (LFR). Seven different mixed-rotor-assembled strands are tested in the current work; they included the mixed-rotor-assemble strand with five different number ratios, Y=3, 2, 1, 0.5 and 0.33, and three total numbers, H=2, 4 and 6, of rotors in each group at Y=1. The obtained results reveal that mixed-rotor-assembled strand with number ratio, Y=1, yields higher mean thermal performance factor than those with other number ratios, Y=3, 2, 0.5 and 0.33 around 3.9%, 8.3%, 18.9% and 15.1%, respectively and the highest thermal performance factor of mixed-rotor-assembled strands at Y=1 with H=2, 4 and 6, are found to be 2.04, 1.96 and 1.85. In addition, the empirical correlations of the heat transfer, friction factor and thermal performance factor are also reported.