A three-dimensional fluid flow model for a self-rotating twisted-tape-inserted tube was presented.The RNG k-ε turbulent model was used to simulate the fluid flow and heat transfer in the self-rotating twisted-tape-inserted tube.The characteristics of fluid flow and heat transfer in the self-rotating twisted-tape-inserted tube were determined.Numerical simulation results showed that the fluid flow was a complex three-dimensional helix flow in the self-rotating twisted-tape-inserted tube.Axial velocity was higher in the annular area near the tube wall than that in the smooth tube; the tangential velocity in the diameter area corresponding to the width of twisted tape increased with the radius.The tangential motion in the annular area between the twisted tape and tube wall was obvious

but the tangential velocity decreased with the radius. However

the tangential motion of the fluid in the smooth tube was only stochastic

and the tangential velocity was smaller by two orders of magnitude.The radial velocity and turbulence intensity were also larger than those in the smooth tube.Due to increase of the axial velocity

tangential velocity

radial velocity and turbulence intensity

the convection heat transfer of the fluid was strengthened and the surface heat transfer coefficient for the self-rotating twisted-tape-inserted tube was larger than that of the smooth tube.In addition

numerical simulation results of the velocity field were compared with the experimental data measured by Laser Doppler Velocimeter （LDV） system.The numerical simulation results showed reasonably good agreement with the experimental data.