Analysis of Cross-Flow Type of Air-to-Air Total Heat Exchangers Made of Functional Paper

Operation of the total heat exchangers (THXs) discussed in this article is based on thin fibrous paper, permeable to moisture but highly impermeable to air, capable of recovering both sensible and latent heat from air. By exchanging sensible and latent heat between fresh air and exhaust air, THXs show great energy-saving potential when fresh air is required for IAQ purposes in a conditioned space. Due to the fibrous permeability of the functional paper, air leakage may occur and, when significant, must be accounted for in evaluating the performance of THXs. In this study, a concept of effective fresh air efficiency defined on the basis of per-unit-effective-fresh-air is proposed and the leakage effect on efficiency is examined with experiments. Both heat and mass transfer effectiveness of THXs were compared with that of the Japan Refrigeration and Air Conditioning Industry Association standards (JRAIA). The results showed that the energy-saving index, or THX effectiveness, of JRA overestimated the performance of THXs if air leakage was present.