Preliminary study on air-to-air latent heat exchanger fabricated using hollow fiber composite membrane for air-conditioning applications

In this study, an air-to-air type hollow fiber composite membrane latent heat exchanger was built and its latent heat exchange characteristics were experimentally investigated under various test conditions. Based on experiments conducted on four prototypes, polyethersulfone with 9 wt% of polyvinyl-pyrrolidone was selected as the membrane material suitable for the latent heat exchanger. Using the selected material, shell-and-tube structured hollow fiber membrane modules were fabricated and tested under various operating conditions. The experimental data showed that the proposed membrane modules exhibited 35.3%-82.7% latent effectiveness and moisture removal rates of 0.027-0.124 g/s under various operating conditions; furthermore, the modules could provide latent cooling with few temperature changes. In addition, the results of the parametric analysis indicated that the inlet primary air humidity ratio was a critical factor affecting the latent cooling performance of the proposed system and the optimal ratio of the secondary to primary air flow was 1.0. The number of mass transfer units (NTUm) in the membrane module design should be higher than 1.7 to attain satisfactory latent cooling performance, that is, higher than 70% latent effectiveness.