Enthalpy exchanger

A heat and moisture exchanger comprising:

• a plurality of panels, each of the panels comprising
• a flexible separator formed to provide projections to either side of a plane of the separator;
• and
• first and second thin water-vapor-permeable membrane sheets attached to the projections on opposing faces of the flexible separator, the flexible separator holding the first and second water-vapor-permeable membrane sheets in a spaced-apart parallel relationship, the panel stiffened by attachment of the membrane sheets to the flexible separator, the projections formed to provide first channels operable for carrying a first flow between the flexible separator and the first and second water-vapor-permeable membrane sheets in a first direction across each of the panels;
• and
• elongated spacers between the adjacent ones of the panels, the elongated spacers spaced apart from one another in the first direction such that the second channels comprise openings having widths 20 times or more a thickness of the panels;
• the panels stacked in a parallel spaced-apart relationship to provide open second channels between adjacent ones of the panels, the second channels extending to carry a second flow through the heat and moisture exchanger in a second direction transverse to the first direction;
• wherein adjacent ones of the panels are spaced apart from one another by distances that are less than a thickness of the panels, and the flexible separator of each of the plurality of panels has a depth that is at least 110% of a height of the second channels.