Laminarization of Low Reynolds Number Turbulent Flow in Heated Rotating Pipe

Numerical investigation of laminarization of low Reynolds number turbulent flow in a heated rotating vertical pipe is carried out using a rotation-sensitized k-omega Shear Stress Transport (SST) model with modifications to include low Reynolds number flow effects. The results show that rotation accelerates laminarization in heated pipes and leads to as much as 72% deterioration in heat transfer for a typical inlet Reynolds number of 5000 and at a rotation number of 2. Rotation causes a reduction of the velocity gradients in the near-wall region. The lower gradients result in a reduction in the rate of production of turbulence kinetic energy, which causes the flow to laminarize. A laminarization map that relates the nondimensional heat flux as a function of inlet Reynolds number and rotation number is presented in this study. Correlation to predict the nondimensional wall heat flux required to laminarize the flow as a function of inlet Reynolds number and rotation number is proposed. The proposed laminarization map and the correlation which predicts the nondimensional heat flux required for laminarization to within an accuracy of +/- 8.1% accuracy for flow of air in a heated rotating vertical pipe would be of value to operators and designers of heat exchangers using air as a working medium to maintain a heat flux or a rotation number below the threshold value to prevent flow laminarization.