Abstract: The fluid flow of self-rotating twisted-tape inserted tube is analyzed. According as tangential motion characteristic of fluid in self-rotating twisted-tape inserted tube, a conception of self-rotating twisted-tape being dummied as equivalent still twisted-tape is put forward. A three-dimensional physics and mathematical model of twisted-tape-inserted tubes are presented. RNG k-e turbulent model is adopted to simulate flow field and enhanced heat transfer of heat exchanger tubes with twisted-tape insert numerically. The distribution laws of the velocity field, pressure field, turbulent characteristic field and enhanced heat transfer characteristic of twisted-tape-inserted heat exchanger tubes are obtained. The heat transfer and pressure drop characteristic of still twisted-tape-inserted tubes, self-rotating twisted-tape inserted tubes and dummy equivalent still twisted-tape inserted tubes are compared. The influences of different twist pitch on enhanced heat transfer and pressure drop are analyzed. Numerical simulation calculation value of the velocity field is compared with the experimental data measured by laser doppler velocimeter (LDV) system. The numerical simulation results show reasonably good agreement with the experimental results.

Key words: Enhanced heat transfer, Heat exchanger tube with twisted-tape insert, Laser doppler velocimeter, Numerical simulation, RNG k-e turbulent model