Simulation of turbulent heat transfer in annular flow with asymmetric wall roughness

The heat transfer in stationary, fully developed annular flow with static or moving cores and asymmetric wall roughness is simulated. In order to describe the fully developed flow field a Reynolds stress model for high Reynolds numbers is derived in the cylindrical coordinate system. The accurate description of the highly asymmetric annular flow is a prerequisite for the heat transfer computation, the turbulence transport properties being known, the heat transfer may be readily computed. The near wall region is described by an appropriate distribution law and using the Boussinesq approach. Temperature and flow fields are computed on two different grids, using a finite difference scheme on stretched grids. The model is validated by comparison with experimental single phase convective heat transfer and pressure loss data for annuli with artificial roughness at the outer wall. For the intensive cooling of hot-rolled wires in cooling tubes with turbulence promoters at the outer, adiabatic wall extensive experimental data is available. The cooling of hot rolled wires with a smooth surface in the film boiling region is modelled, using an equivalent roughness for the turbulence promoters.