A three dimensional mathematical model for a heat transfer tube with a self-rotating cleaning twisted-tape insert are presented. The RNG k- ε turbulent model is applied to simulate the flow field in the tube. The flow characteristics and heat transfer are obtained. The results show that the behavior of fluid flow in the tube with the self-rotating cleaning twisted-tape insert is different from that in a smooth tube, and it is a complex 3D helix rotating flow. The axial velocity is higher near the tube wall region than that of the smooth tube, and the tangential velocity increases as the radius. However, the tangential motion of the fluid in the smooth tube is only stochastic, furthermore the tangential velocity in the smooth tube is less about 2-quantity level than that in the twisted-tape tube. The radial velocity and turbulence intensity are larger than that of the smooth tube. Because the axial velocity near the tube wall region, the tangential velocity, the radial velocity and turbulence intensity increase, they strengthen the convection heat transfer of the fluid, and the surface heat transfer coefficient in the tube with a self-rotating twisted-tape insert is larger than that of the smooth tube. In addition, the numerical simulation results of the velocity field have been compared with the experimental data measured by Laser Doppler Velocimeter (LDV) system. The numerical simulation results show reasonably good agreement with the experimental results.
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