New heat wheels for GEA CAIR<i>plus</i> and COM4<i>plus</i> central air-handling systems assures low pollution of room air served by heat recovery
15. January 2014 GEA Heat Exchangers now offers its two air-handling units of CAIR<i>plus</i> and COM4<i>plus</i> series with sorption-type rotary heat exchangers for heat recovery with 3A molecular sieves. Thanks to these molecular sieves, the new rotary heat exchanger effectively transfer thermal energy and humidity from extract air to supply air – but transfer virtually no volatile organic compounds (VOC gases).
An industrial study, in collaboration with Luzern Technical College (Switzerland), confirmed that air conditioned with the new rotary heat exchanger absorbs less odorous substance and pollution than air conditioned with a conventional sorption wheel. In a test for trace gases with the new heat wheel, the total transfer rate of all volatile organic compounds was only 3 % during summer operation, and only 4 % during winter. In comparison, a rotary heat exchanger with conventional silica gel demonstrated a total transfer rate almost ten times greater: during summer operation, the total transfer rate of the silica-gel heat wheel was 24 % and in winter, 36 %.
Throughout the entire year, sorption rotors result in high levels of humidity transfer and can consequently considerably reduce the energy required for humidification or dehumidification of supply air. Here, humidity transfer takes place by means of the coating of the rotor matrix: a material that adsorbs humidity and transfers it to the other air flow.
The fact that the new rotary heat exchanger transfers virtually no VOC gases is the result of the adsorption capability of its fine coating. Whereas a silica-gel coating demonstrates a relatively coarse and undefined pore structure, and adsorbs almost all molecule sizes, the surface of the molecular sieve captures only small molecules with diameters ≤ 3 Å, (a water molecule has a diameter of 2.7 Å). Molecular sieve systems accordingly do not transport large organic compounds.
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