Droplet deposition in radial turbines

In this paper droplet deposition in radial turbines used for waste heat recovery in the chemical industry is investigated. During expansion, the water vapour in the working fluid undergoes sub-cooling, at a certain point a cloud of fine droplets begins to form and a fraction of these droplets is deposited on the blade surfaces. In this paper, droplet deposition is calculated by incorporating turbulent fluctuations and Brownian motion into a Lagrange particle tracking algorithm. After introducing the calculation approach, a validation of the enhanced CFD code by means of deposition experiments in a straight tube is presented. For a radial turbine, the functional relation between the location of maximum sub-cooling and the onset of droplet deposition is pointed out. Even though the validation of the numerical code is quite satisfactory, some uncertainties arise from the nucleation modelling. This uncertainty will be addressed in the publication as well. The paper concludes with suggestions on how to increase the reliability of the calculations.