Motion of water drops on hydrophobic expanded polymer mat surfaces due to tangential air flow

Hydrophobic expanded polymer mats are used in a wide range of industries for many purposes. Their relatively low cost, availability in a wide range of polymer materials, and consistency of pore size distribution are advantageous for some applications such as the separation of liquid drops from gas streams. When fabricated of a non-wetting material, liquid drops tend to stay on one side of the mat and can move across the mat surface due to drag of the gas flow. The rate of movement of drops on the surface can affect the rate of coalescence, the drop size, the loading of drops on the surface of the mat, and ultimately the effectiveness of the mat to separate the drops from a gas stream. In this work the movements of water drops on the surfaces of expanded polymer mats due to tangential air flow are observed to determine the effects of mat material properties and geometrical characteristics, drop dimensions and air flow conditions. A correlation for a drag coefficient of drop movement on the mat surface is developed. A second correlation for the minimum Reynolds number of the gas to initiate the movement of drop on the surface of the mat is also developed. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.