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

The article presents an experimental study of turbulent heat transfer and flow characteristics in a circular tube equipped with single spiral slot rotor (SSR)-assembled strand, single low flow resistance rotor (LFR)-assembled strand and rotor-assembled strands mixed by spiral slot rotor (SSR) and low flow resistance rotor (LFR). Five different mixed-rotor-assembled strands are tested in the current work; they included the mixed-rotor-assemble strand with three different number ratios, Y = 2, 1 and 0.5, and three total numbers, H = 3, 6 and 9, of rotors in each group at Y = 2. The obtained results reveal that mixed-rotor-assembled strand with number ratio, Y = 2, yields higher mean thermal performance factor than those with other number ratios, Y = 1 and 0.5 around 2.83% and 1.64%, respectively and the thermal performance factor decreases with increasing total number (H) of rotors in each group when number ratio is at a constant value Y = 2.