Proof of Concept

The feasibility of using commercially available membranes for capillary condensation and subsequent transport of condensate into a salt solution was demonstrated first in a laboratory scale experiment.  A glass container, filled to the top with a salt solution, was covered with a membrane.  A narrow tube attached to the side of the container extends up above the container.  Humid air was blown across the top of the membrane and the rate of removal of water from the air was measured by the change in liquid level in the tube.  Membranes tested were those used commercially for water purification.  Salt solutions that were very effective were lithium chloride and magnesium chloride.  The latter salt is inexpensive, benign and readily available.

Results suggest that 1 square meter of the membranes that worked most effectively removes about 0.7 liters/hr of water vapor at relative humidity levels between 80 and 90%.  The rate of condensation per unit of surface area is considerably smaller than for a uniform pore size capillary condenser.  However, the polymer membranes are stable, inexpensive, flexible, and offer simple methods for providing large surface area interfaces between humid air and films of liquid salt solution.