A study of the efficiency of recovery of micron size droplets from high velocity air-liquid mixtures in a centrifugal field, employing a metal and plastic porous disc

• Main Author: Gunawardana, Wahalathanthriga Dhanapala
• Published: University of East London 2002
• Subjects: 551.57
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532487

This work is specially contributes to the knowledge in the field of efficient removal of entrained micron size liquid drops from air mist in a centrifugal field using bimetallic and bi-surface (low and high energy) porous discs. The available equipment was suitably modified, commissioned and utilised in this investigation. The variables investigated include: different rotational speeds; various air and liquid flow-rates; three materials of construction and five porosities of the rotating porous discs. The average residence time of two-phase two-component flow of fine air mist through the rotating porous disc was in the range of 0.7ms to 3.0ms. A high-resolution and magnification optical method has been used to record, explain and understand the mechanism of wettability of the bi-metal and bi-surface energy porous discs. Navier-Stokes equations of momentum have been used to develop a mathematical model to predict the width of a liquid film formed on top of the rotating porous disc. The predictions of the model compared very favorably with the experimental data. The final empirical equations that represents the separation efficiency, (45 to near 100 %) of the bi-metallic and bi-surface energy (high and low) porous disc rotating at, 0+ to 6100 r/min, are [equation 1] for inline arragement of openings/holes in the porous disc. And [equation 2] for staggered arrangement of openings/holes in the porous disc. Artificial neural networks have been successfully used for the modelling and correlation of experimental data, collected from six porous discs with five porosities and three materials of construction with high and low surface energies, on percent separation efficiency from mixture of air-water mist. The correlation coefficient between the experimental and predicted separation efficiency was found to be 0.95. The Lockhart- Martinelli approach has been used to develop an empirical equation for the constant B, as defined by Lockhart- Martinelli that may be used for the calculation of co-current plus cross-current two-phase two-component pressure drop in this system. [equation 3] An empirical equation that has been developed to predict the liquid film's width is [equation 4] The correlation coefficient between the experimental and predicted film widths was found to be 0.92. Equations 1 to 4 may be used to design a new system for the continuous removal/separation of entrained micron size drops from high velocity air mist.