Modified upright cup method for testing water vapor permeability in porous membranes

Abstract A membrane based heat and mass exchanger is a promising technology used to control both sensible and latent loads. Membranes are porous materials that allow water vapor transmission from one medium to another. Water vapor permeability of these membranes is the key parameter for establishing their performance. Various techniques exist to measure the water vapor permeability in membranes of different types and characteristics. The most commonly used is the cup test based on the standards published by The American Society for Testing and Materials (ASTM). The upright cup test described in the ASTM E96 standard is mainly used to predict the values of low to moderate permeable materials where the air resistance above the cup is relatively small. This paper briefly describes the ASTM test and introduces a modified technique that infers the water vapor transmission in highly permeable materials considering explicitly the air resistance. Different porous materials, initially manufactured for considerations other than operating as membranes, are identified and experiments are conducted to derive their permeability using an identification method. The results of the experiments are subjected to an uncertainty analysis to assess the accuracy of the measuring technique showing acceptable values ranging from 8% to 26%.