Design and selection of curved vane demisters using Taguchi based CFD analysis

The present work discusses the design and selection of a curved vane demister as used in seawater desalination. A baseline design of a curved vane demister was chosen and the key geometrical parameter which influences the demister performance was identified. To optimize the curved vane demister geometry with multiple parameters with multiple levels, a design of an experiment approach using Taguchi method was chosen to select an orthogonal array of 25 designs. Numerical computations for the water vapor flow carrying water droplets in different curved vane geometries, with options like Wave droplet breakup and Realizable k-ε turbulence model using Fluent 14.0, were carried out. Water droplets were injected using discrete phase modeling approach and Rosin-Rammler size distribution at four vapor velocities of 5, 7.5, 10 and 12.5 m/s. The mean water droplet diameter, the Sauter mean diameter and the droplet separation efficiency along with the associated pressure drop were estimated, compared and reported. The values of the lowest friction factor and the highest separation efficiency were found to be 2.54 and 99.98% for one case and 1.88 and 99.29% for another case respectively. With a little compromise on pressure drop, the former case may be considered as the best, as it has the highest water droplet separation efficiency.