The calculation of wave-plate demister efficiencies using numerical simulation of the flow field and droplet motion

In this paper the collection efficiency of two wave-plate demisters is calculated by numerically simulating both the turbulent gas flow through the demisters and the droplet motion. Comparison of the numerical results with experimental data(1) reveals that (i) the numerical prediction of the collection efficiency based on a low Reynolds number k - epsilon turbulence model coincides better with that found from experiments than the numerical prediction based on the standard k - epsilon turbulence model and that (ii) the separation cut-off points predicted numerically agree well with those found from experiments. In addition, the numerically predicted efficiency curves have the same trends as those obtained experimentally. However, large discrepancies exist between numerically predicted and measured collection efficiencies over a range of droplet sizes. These are probably due to the fact that the influence of turbulence on droplet motion has not been included in the numerical simulation. It is also found that the amount of liquid in the first bend of the demisters formed by the deposited droplets increases significantly with the bulk gas speed and that over 70% of the total amount of trapped water in the demisters is within the first two bends in the cases when the bulk speed is 2ms(-1) and 5ms(-1). Suggestions for improved design of wave-plate demisters are made accordingly.