Phase-Separation of Wetting Fluids

Phase separation in two-phase microfluidic exchangers is a promising strategy for reducing the required pumping power. Past research has focused on using hydrophobic nanoporous structures in order to extract water vapor and retain liquid within the vapor-cooling device. This study focuses on characterizing the bursting pressure, the maximum Laplace pressure for liquid containment, of nanoporous alumina membranes and micro-glass capillaries. The pore size diameters of the alumina membranes have a nominal diameter of 170 nm that can produce a pressure drop of 1.5 kPa for wetting dielectric liquids. In order to contain higher Laplace pressures, the pore geometry for ‘pinning’ of the fluid at the liquid-vapor interface needs to be optimized. Single glass micro-glass capillaries were used in order to study the ‘pinning effect’ of wetting fluids for various micro-capillary diameters. The glass capillary diameters ranged from 250-840 µm with measured Laplace pressures up to ~0.9 kPa. Experimental results agreed well with an analytical model that calculates the Laplace pressure as a function of pore geometry.

Agonafer, D.D., Lopez, K., Won, Y., Palko, J., Asheghi, M., Santiago, J.G., Goodson, K.E., “Phase-Separation of Wetting Fluids Using Nanoporous Alumina Membranes and Micro-GLASS Capillaries”, IEEE Intersociety Conferenceon Thermal and Thermomechanical Phenomenain Electronic Systems (ITHERM) 2014, May20 – 20, Orlando,FL,USA.