Moisture diffusion coefficients of a PE/PA composite membrane in an enthalpy exchanger for heat and moisture recovery

Abstract

Paper membranes have long been used in an enthalpy exchanger. However, there has been a continuous concern on the durability or the anti-bacterial performance. In this study, heat and moisture transfer characteristics of a recently-developed PE/PA (polyethylene/polyacetate) composite membrane was investigated as a possible substitute to the paper membrane. Results showed that the diffusion coefficients of the PE/PA membrane (7.7 × 10−10 m2/s to 1.8 × 10−9 m2/s) were higher than those of the paper membrane (1.8 × 10−11 m2/s to 6.0 × 10−11 m2/s). Furthermore, the diffusion coefficient increased as relative humidity increased, reached a maximum at 50 % to 60 % and then decreased. For PE/PA membrane, the sorption constant increased as temperature increased, which was the reversed trend to the paper membrane. Successful prediction of the moisture transfer effectivenesses of the separate pseudo-counter flow enthalpy exchangers further strengthened the validity of the obtained diffusion coefficients.