of moisture removal is achieved with affordable vacuum pump
energy consumption.
Recently, Scovazzo et al. [2] have reported significant dehumidification
performance at a permeate pressure much higher than
the partial water vapor pressure in the feed air. The researchers
extracted some of the air from the output air stream and introduce
back into the permeate stream as a sweep gas. In this manner, the
concentrated water vapor in the permeate stream is diluted with
the sweep air. Therefore, the partial water vapor pressure in permeate
stream is reduced significantly, which leads to a higher driving
force for water transmission through the membrane. We
observe this dilution effect when low selectivity membranes are
used. It means that lower membrane’s selectivity gives higher
dehumidification performance at higher permeate pressure. An
interesting question arises if lower selectivity implies higher dehumidification
COP?
In this work, we report the fabrication of composite membranes
from stainless steel wire mesh, porous titania and hydrophilic
poly(vinyl alcohol) with varied water vapor permeability and
selectivity. Based on the characteristics of the synthesized membranes,
the feasibility of the membrane-based isothermal dehumidification
is systematically investigated. Key factors
influencing the dehumidification performance and COP of a membrane
system such as permeate pressure, velocity and RH of the
feed air, permeability and selectivity of the working membrane
are studied through experiments and numerical analysis