Heat transfer enhancement in the tube fitted with Left–Right helical blade rotors

• Nusselt number increased with the decreasing numbers of Right helical blade rotors.
• Friction factor increased with the decreasing number ratios.
• Thermal performance factor increased with decreasing Right helical blade rotor number.

The thermohydraulic characteristics of the circular tube equipped with Left–Right helical blade rotors were reported; meanwhile, the influence of the assembled mode of Left–Right helical blade rotors on heat transfer, friction factor and thermal performance factor characteristics of the enhanced tube was also investigated. The experimental results revealed that the Nusselt number and friction factor of the tube with helical blade rotors was 77.9–182.2% and 22.1–71.1% higher than that of plain tube, respectively. The Nusselt number of the tube with Left–Right helical blade rotors increased with the decreasing numbers of Right helical blade rotors; the enhanced tube with the ratio of Left–Right helical blade rotors number as 1/3 generated the highest Nusselt number than others. The friction factor of the enhanced tube increased with the decreasing numbers of Right helical blade rotors and the decreasing number ratios. The thermal performance factor of Left–Right helical blade rotors increased with the decreasing number of the Right helical blade rotor; meanwhile, the enhanced tube with the ratio of Left–Right helical blade rotors number as 1/3 generated the highest thermal performance factor.